PITTSBURGH CONFERENCE ABSTRACTS

Pittcon 2020

PP110 - Online Analysis of Mercury in Water with Part Per Trillion Detection Limits

Authors: Dr Warren Corns, Shaun Lancaster, Jasmina Allen and Yasmin Vaeli (PSA)

In 2015, the US EPA finalized a rule revising the regulations for the Steam Electric Power Generating category (40 CFR Part 423). The EPA ruling is an attempt to reduce the amount of toxic metals and other pollutants discharged to surface water from power plants. The main pollutants of concern include metals (e.g Hg, As and Se), nitrogen and total dissolved solids (TDS). Toxic metal discharges have a huge impact on the environment as they bio-accumulate in wildlife and cause a wide array of human health issues. The new ruling will establish new and additional requirements for wastewaters associated with FGD wastewater, fly and bottom ash transportation water, flue gas mercury control water, combustion residual leachates from landfill and surface impoundments, metal cleaning wastes and gasification wastewater. In this poster we will provide an overview on our new online based AFS instrument for mercury. The system is based on oxidative UV photolysis of Hg with cold vapour gold amalgamation – AFS. The instrument was developed to meet the forthcoming effluent discharge limits for the USA which requires a discharge limit of 12ng/L (ppt). The system has been designed to minimize reagent consumption by use of syringe automation and batch analysis. Detection limits are achieved by the use gold amalgamation and the use of small quantities of high purity reagents. The poster will present analytical performance characteristics and also comparison data with offline EPA 245.7 mercury measurements from real waste water samples collected in the field.

PP111 - Occupational Study of Mercury in the Oil and Gas Industry

Authors: Dr Warren Corns, Jasmina Allen and Tony Rogers (PSA)

Mercury is toxic elemental that is hazardous to human health even at low concentrations of exposure. Chronic occupation exposure can lead to a large number of symptoms, including motor impairment, excess salivation, insomnia, memory losses, gingivitis, erythrism and behavioural changes such as excitability and excessive shyness. As mercury is an accumulative poison these symptoms may appear later in life even after the period of exposure has ceased. In the Oil and Gas Industry mercury is present in gas, condensate and produced water in various forms over a wide concentration range. Identifying the sources or mercury, concentration levels and its chemical forms are the first steps in managing the risks to employees. It is also important to identify the process equipment and components where Hg may accumulate, job activities where exposure may occur and the higher risk exposure groups. Understanding these factors provides important information on how to manage and to minimize exposure rates to Hg. In this poster, we will present and review the analytical methods and instrumentation required to provide a comprehensive mercury occupational survey for both offshore and onshore production facilities. The paper will focus on the use of Atomic Fluorescence Spectrometry for the determination of Hg in various process related samples such gas, condensate, water, glycols, amines, spent adsorbents, residues, sludges, pipe scale, spent filters and gas vents. In addition to the results of wipe samples and personal exposure monitoring tubes in relation to job occupation and activities will be presented.  

PP112 - Passive Sampling of Hg in Ambient Air using Gold Amalgamation with Atomic Fluorescence Spectrometry

Authors: Ben Jones, Dr Warren Corns and Tony Rogers (PSA)

Mercury is an air pollutant of global concern because of its high toxicity and ability to bio-accumulate in the food chain. Currently the monitoring of mercury is ambient air is not extensive due to the limited number of monitoring sites around the globe. Cost effective monitoring solutions are therefore required in order to facilitate extra mercury vapour monitoring, because the sources of mercury vapour are different to those of other pollutants and therefore may require specific monitoring locations. This poster presents the validation and application of existing, gold on silica AmasilTM adsorption tubes designed for pumped mercury vapour sampling as passive samplers. The uptake rates of these tubes have been found to be low (approximately 0.215 ml/min) as compared to bespoke passive samplers for mercury vapour which are typically in the range of 20-50 ml/min. When deployed in the field for several months they pre-concentrate a sufficient mass of mercury to be analytically measured by dual-amalgamation AFS. One of the advantages of using these tubes is that they can be analysed in the lab by thermal desorption without the need of wet digestion methods. After establishing a blank, the tubes can therefore be re-used.

The uptake rate of each batch of tubes was determined using the micro-exposure chamber in combination with a dynamic Hg Generator prior to deployment. The output of the generator was certified using a SI Traceable Hg generator as part of the MercOx project1. Results have shown that the uptake rate determined in the micro-exposure chamber is invariant of concentration, and therefore these uptakes rates may be determined at a high mercury vapour concentration for many tubes at once in less than one hour. The uptake rate of the adsorption tubes under these conditions may be determined with a precision of 5%. Measurements made on various field trials in indoor and outdoor ambient air locations. This work has shown that these tubes give results in acceptable agreement with more traditional pumped sampling methods, although longer sampling periods are required in order to reduce the uncertainty of the measurement, which is currently approximately 30%.

1, EMPIR Project 16ENV01 MercOx – Metrology for Oxidized Hg

 

Pittcon 2019

PP103 - Overcoming the effect of dissolved acid gases for analysis of total mercury in foodstuffs by CV-AFS after closed digestion

Authors: Jasmina Allen, Shaun Lancaster and Dr Warren Corns (PSA)

It is common practice in food labs worldwide to digest samples using closed digestion vessels with concentrated acids at high temperature. In European food labs they must follow a set digestion procedure described in European Standards Method 13805 when analysing metals in foodstuffs. However, this method requires closed vessel microwave digestion with concentrated nitric acid, which generates dissolved gases such as NOx in the digest sample that can cause quenching of mercury fluorescence, rendering the digestion method incompatible with the highly sensitive cold vapour – atomic fluorescence spectrometry (CV-AFS) approach. Thus, creating a secondary step that works in accordance with the European Standards Method is of paramount importance.

A secondary digestion step using hydrogen peroxide with microwave digestion, followed by a cold bromination step, was employed to overcome the effect of dissolved gases in the sample digest. The use of these steps applied after the nitric acid digestion was found to significantly improve the precision and accuracy when analysing with CV-AFS. Preliminary studies have been carried out using 6 certified reference materials including fish, rice, chicken, and poplar leaf matrixes. The initial measurements showed good precision on measurements of each reference material, generally less than 5% RSD, and recoveries of mercury ranging from 82 – 105%.

PP104 - Hg, As and Se determination by photochemical vapour generation - AFS: Challenging Industrial Applications

Authors: Shaun Lancaster and Dr Warren Corns (PSA) and Jorg Feldmann and Eva Krupp (University of Aberdeen)

The determination of Hg or hydride forming elements, e.g. As and Se, by cold vapour- or hydride generation-atomic fluorescence spectrometry (AFS) is a well-established technique. Traditionally, cold vapour or hydride generation is carried out using tin(II) chloride or sodium borohydride respectively. However, these methods use a plethora of chemicals which is costly and prone to error, as well as instrumental issues due to the complex wet chemistry necessary.
Another pathway is photochemical vapour generation (PVG), which has been used in conjunction with AFS as an alternative vapour generation method. PVG of hydride forming elements using UV with formic acid has been widely studied in the past. Recently, PVG has been applied to total mercury measurements using UV with formic acid or acetic acid. PVG promises a simpler, more cost effective approach with fewer, greener chemicals, achieving results comparable to the traditional approach.

A new online system for industrial wastewater discharge samples based on oxidative UV photolysis of Hg with amalgamation – AFS was developed to meet the forthcoming effluent discharge limits for the USA. A new effluent discharge limit of 12ng/L has been set which is an extremely demanding online measurement given the complexity of the matrix. The system will be modified to also analyse As and Se via hydride generation – AFS. PVG will be applied, evaluated and critically compared to traditional chemical vapour and hydride generation methods.

PP105 - Development of an online direct mercury analyser for workroom air monitoring

Authors: Dr Warren Corns, Tony Rogers and Robert Kennett (PSA)

Mercury is toxic elemental that is hazardous to human health even at low concentrations.  The nervous system is considered to be the main organ affected by mercury vapour. Chronic occupation exposure can lead to a large number of symptoms including motor impairment, excess salivation, insomnia, memory losses, gingivitis, erythrism and behavioural changes such as excitability and excessive shyness. These symptoms may appear later in life even after the period of exposure has ceased.  Despite this knowledge mercury continues to be used in various industrial processes and there is an increasing trend to recycle and recover mercury to control its emission to the environment. Occupational exposure of elemental mercury in the workplace therefore has to be carefully monitored. Hg exposure is typically monitored via urine testing programs and passive badges. These approaches however do not alert staff of a high exposure level until after the event has taken place. Handheld Hg sniffers are commercially available and offer a more rapid response. These however are not used in a continuous fashion and are more typically used to spot check concentration levels. On site calibration of these devices can be issue and more often that not they have to be returned back to the supplier for calibration. This lack of calibration leads to a mistrust of the readings and an anxious workforce. In this work, we will describe a newly developed direct online Hg measurement system. The system comprises a touchscreen computer coupled with one or two atomic fluorescence spectrometers. Each spectrometer consists of a low pressure Hg lamp as an excitation source with a photomultiplier for detection. Each detection system is capable of connecting to multiple sample probes so that multi-room monitoring can be achieved. The analyser measures gas phase mercury and depending on configuration has a measurement response time of less than 30 seconds. A dynamic elemental Hg calibration system is integrated into the system to enable zero and span adjustment on a user defined interval basis. Detection limits are well below the typical exposure limits imposed for workroom air (20µg/m3) with an upper linear working range exceeding 1000µg/m3.

 

Pittcon 2018

PP099 - Title: Metrological Development and Evaluation of Oxidised Hg Calibration Systems

Authors: Warren Corns, Matthew Dexter and Shaun Lancaster (PSA)

The development of SI traceable measurements for the monitoring and control of mercury in gas emission sources and in the atmosphere is of prime importance for various groups, including mercury researchers, plant operators, regulators and also for the implementation of the Minamata Convention. Currently traceable calibration systems only exist for elemental Hg however such requirements are also required for oxidized Hg species namely (Hg2+).

Knowledge of Hg speciation in both air and in stack emissions is critical when validating models for predicting Hg emissions, transportation, deposition and fate on a global scale. Numerous methods and instrumentation exists for gas phase Hg speciation although this is rarely calibrated for oxidized Hg and if so the metrology of the calibrator is unknown. This raises the uncertainty of the speciation measurement and also inhibits the development of new measurement protocols.

The MercOx project is a European funded EMPIR Metrology project to develop traceable Hg online measurements for gas emissions and the atmosphere. In this paper we will provide an overview of our research work on the development and metrological assessment of various oxidised Hg calibration systems. Approaches include liquid evaporative HgCl2 generators, HgCl2 permeation devices, dilution of saturated sources of HgCl2 at known temperature, catalytic oxidisation of elemental Hg and ultra-sonication of aqueous HgCl2 solutions.

These approaches will be coupled to various wet chemical, sorbent trap and Hg-CEM mercury speciation measurement technologies.

PP100 - Determination of Inorganic Arsenic in Melarsomine Dihydrochloride Active Pharmaceutical Ingredient

Authors: Warren Corns and Jasmina Allen (PSA)

Melarsomine dihydrochloride is an organic arsenical chemotherapeutic agent used as an API for the treatment of cannine heartworm caused by Dirofilaria immitis. As part of a FDA requirement the API has to contain less than 250ppm of inorganic Arsenic based on the summation of Arsenate and Arsenite.

The test is challenging as the API contains 14% by mass of Arsenic which can affect the measurement technique by causing contamination and carryover between samples. Chromatographic separations were developed to not only separate Arsenate and Arsenite but also to flush the API agent from the column.
Method Development and validation was conducted using Ion chromatography with Hydride Generation – Atomic Fluorescence Spectrometry.  A summary of the validation data according to VICH GL2 guidelines will be presented. Validation of the method included a detailed study of system suitability, specificity, linearity, accuracy, precision, robustness, limit of detection, limit of quantification and ruggedness.

PP101: Greener and more cost effective analysis of methylmercury using acetic acid with LC-UV-CV-AFS

Authors: Shaun T. Lancaster, Jonas Kunigkeit, Warren T. Corns, Jörg Feldmann, Eva M. Krupp (University of Aberdeen and PSA)

A reliable method for the analysis of mercury species is cold vapour generation of mercury coupled with atomic fluorescence spectroscopy. The most commonly used method of cold vapour generation involves oxidising all organic mercury species to inorganic mercury (Hg2+), followed by a reduction to elemental mercury (Hg0) with tin(II) chloride or sodium borohydride. However, this method uses a plethora of chemicals which is both costly and prone to error as well as instrumental issues due to the complex wet chemistry necessary.

Another pathway is photochemical vapour generation (PVG), which has been used in the past in conjunction with a variety of detection methods such as atomic fluorescence spectroscopy (AFS) as an alternative method of cold vapour generation. PVG has been applied to total mercury measurements using UV with formic acid and acetic acid. In addition, the total mercury concentration in white vinegar was determined by matrix assisted photochemical vapour generation. PVG promises a much simpler and more cost effective approach, which uses fewer and more environmentally friendly chemicals to give results which are comparable or even more sensitive than the chemical vapour generation approach.

Here we apply acetic acid photochemical vapour generation of mercury to speciation measurements to provide a much simpler analysis of methylmercury in four selected matrices: seafood, hair, sediment, and rice. In total, 9 certified reference materials were analysed to assess the accuracy and precision of the method. A comparison was made for the methylmercury signal obtained between the PVG and CVG methods, which showed that the PVG method provided a sensitivity equal to that of the CVG method.

Pittcon 2017

PP095 - Arsenic Speciation in FGD Wastewater Samples using Liquid Chromatography - Hydride Generation Atomic Fluorescence Spectrometry

Authors: Dr. Warren T Corns & Jasmina Allen (PSA), Shaun Lancaster, Eva Krupp & Joerg Feldman (Aberdeen University

The EPA rule for Effluent Guideline Limits (40 CFR, part 423) is an attempt to reduce the amount of toxic metals and other pollutants discharged to surface water from power plants. Previous regulations did not consider the additional burden of water discharge pollutants from air pollution control systems such as flue gas desulphurization (FGD).

The main pollutants of concern include metals (e.g Hg, As & Se) , nitrogen and total dissolved solids (TDS). Toxic metal discharges have a huge impact on the environment as they bio-accumulate in wildlife and cause a wide array of human health issues.

The best available technology (BAT) that is economically achievable will need to be applied to reduce pollutant discharges. This is particularly challenging for dissolved forms of As, Se and Hg as they are not removed by surface impoundments. In addition waste streams cannot be comingled to achieve high dilution rates to meet discharge limits without first establishing pollutant levels.

Monitoring these streams is not easy because of the low concentrations that have been proposed, high dissolved solids and potential of sample matrix interference.

Online and laboratory measurements based on AFS will be used to confirm the efficiency of the wastewater treatment processes and for compliance monitoring. In this poster we will describe a system for arsenic speciation based on ion-chromatography coupled to hydride generation atomic fluorescence spectrometry. The measurement technology will be applied to the analysis of FGD wastewater samples. The importance of reliable arsenic speciation measurements in this type of sample will discussed in relation to the development of abatement systems for wastewater treatment technology. The summation of arsenic species detected will be compared to total arsenic measurements. Analytical performance data including detection limits, linearity, accuracy, precision and spike recoveries on real samples will be presented.

PP096 - Determination of Selenium Species in Bottled Mineral Water Causing Odour and Tainting

Authors: Dr. Warren T Corns & Jasmina Allen (PSA), Shaun Lancaster, Eva Krupp & Joerg Feldman (Aberdeen University

Bottled water is perceived to be healthier than tap water and as such more than 75 billion gallons of bottled water is estimated to be consumed worldwide per annum. Mineral water is defined as water from underground sources and microbiologically healthy. Bottled mineral water contains characteristic bacterial flora and microorganisms that are naturally occurring. In some cases the bacteria may be introduced as a contaminant during the collecting, processing and bottling stage. No treatment can be applied to the water that changes its natural composition and as such the only processes allowed are filtration, oxygenation, settling and treatment with ozone-rich air.

The presence of volatile selenium species such as dimethylselenide and dimethyldiselenide even at part per trillion ranges may cause objectionable odours similar to rotting cabbage and garlic. The standard method of analysis based on solid phase micro-extraction with GC-MS does not offer sufficient detection limits to quantify these species at the ppt level and furthermore it does not provide determination of non-volatile selenium species. In this paper we will report our findings on the development of techniques based on Atomic Fluorescence Spectrometry for this application. Bottle water samples with and without selenium odour issues will be analysed. Samples directly from the source prior to bottling will also be tested to see whether or not the volatile selenium species are formed during storage or processing or are present at source.

Pittcon 2016

PP090 - Online Analysis and Speciation of Antimony in Various Wastewater Streams using Hydride Generation - AFS

Authors: Dr Bin Chen, Dr Warren T Corns & Dr Peter B Stockwell (PSA)

Antimony levels in drinking water are generally quite low and not considered a major health concern. However it is used in various industrial processes and is discharged in wastewater. Antimony compounds are used as catalysts in the production of polyesters and flame retardants and these ultimately cause releases of antimony to the environment during production and disposal. In June 2013, the EPA proposed a new rule “40 CFR Part 423” which relates to effluent limitation guidelines to limit the amount of toxic metals being discharged to surface waters. Antimony is one of the main elements of concern because of its high toxicity and potential impact to the environment and wildlife. Online analysis of Sb in wastewater streams enables the possibilities of precise monitoring of the complete water treatment process and ensures the compliance with discharge regulations. However the analytical challenges remain due to the complexity of the wastewater matrix. Hydride generation is also oxidation state dependent and therefore online chemistries have to be developed to ensure accurate measurements are achieved. In this presentation, various industrial wastewater streams are successfully analysed by online analysis based on hydride generation atomic fluorescence spectrometry (HG-AFS). . Detection limits of 200 ppt with linearity to 100 ppm are achievable with the online instrumentation. The results were compared and cross examined by HPLC-HG-AFS and HG-AFS methodologies after the appropriate sample treatments.

PP091 - Speciation of Mercury in Rice with a new Online Pre-concentration HPLC-CV-AFS method

Authors: Cornelius Brombach, Piumi Kolambage Dona, Dr Bin Chen and Dr Warren T Corns (PSA), Eva Krup and Joerg Feldmen (Aberdeen Uni)

Rice is a global staple food and can provide up to 75 % of a person’s dietary energy supply. It is now accepted that rice is a mercury accumulator. Methylmercury (MeHg) is powerful neurotoxin so the monitoring of this species in rice is crucial.

We developed a speciation method for rice, which is based on an alkaline digestion and leaching extraction, the subsequent online pre-concentration and HPLC-CV-AFS detection.

A market study was done, where 87 commercial rice products (from the United Kingdom, Germany, Switzerland, Taiwan and China), including baby-food rice, were analyzed for total Hg and methylmercury content.  MeHg was analyzed with another independent method called species-specific isotope dilution GC-ICP-MS. The results for both methods were found to be in good agreement and a correlation coefficient of 0.972 and a slope of 1.013 was found.

The MeHg concentrations in all rice products investigated range from 0.11 to 6.45 µg kg-1 with an average value of 1.91 ± 1.07 µg kg-1. Total Hg ranges from 0.53 to 11.1 µg kg-1 with an average of 3.04 ± 2.07 µg kg-1. MeHg is the main Hg species with 71 ± 26 % of total Hg but can be as low as 6 % and as high as 100 %. Whilst these results seem relatively low, the mercury dietary contribution to infants and populations consuming large rice quantities is significant especially if the person also consumes fish products or has additional exposures to Hg.

This work clearly demonstrates the need for detailed food surveys to accurately determine MeHg in rice and rice products.  

PP092 - Speciation of Organic Mercury in Water Samples by Alkylation, Organic Solvent Extraction and GC-AFS Detection - A Comparison of Ethylation, Propylation and Phenylation

Authors: Cornelius Brombach, Dr Warren T Corns and Dr Bin Chen (PSA) and Jun Yoshinaga (University of Tokyo)

Gas chromatography is an established method for mercury speciation coupled to ICP-MS or AFS. AFS offers a low cost alternative to ICP-MS with similar analytical performance characteristics. The EPA method 1630 uses distillation, ethylation, and purge and trap for speciation of MeHg. Distillation in combination with purge and trap is known to form artefacts of MeHg in sediments and is a time-consuming step. The use of Ethylation also masks the determination of ethylmercury which may be important in certain biogeochemical ecosystems such as the Florida Everglades and for wastewater discharges from industrial sources.  In this work, we use the extraction of the alkylated species into an organic phase and then the direct injection of the extract into GC-AFS. This eliminates the purge and trap requirement thus simplifying instrument and reduces measuring times. This approach was tested with sodium tetraethylborate, sodium tetrapropylborate and sodium tetraphenylborate and the advantages and disadvantages of each alkylation reagent are presented. Various water samples including drinking water, river water, seawater and wastewater were tested using the methods developed and these findings will be reported.  

PP093 - The Determination of Mercury in Liquefied Petroleum Gas - A Comparison of Sampling Techniques

Authors: Dr Matthew A Dexter, Tony Rogers and Dr Warren T Corns (PSA)

Liquefied petroleum gas (LPG) is a mixture of C3 and C4 compounds, primarily propane and butane.  LPG is pressurised to maintain it in the liquid phase to facilitate storage and transport and vaporised when used.  The mercury concentration in LPG is typically measured by atomic spectroscopy-based methods, following vaporisation of a representative sample.  Various sampling techniques are available, many of which use amalgamation-atomic-spectroscopy based analysis techniques:

         1. Vaporising the LPG sample in the field using a heated regulator, followed by collection of mercury from a known volume of sample by amalgamation onto gold for subsequent analysis.

         2. Collecting a liquid LPG sample in a sample bomb for laboratory analysis.  A low flow of gas is then extracted from the vessel into a Tedlar bag for analysis as a gas.  Mercury from a known volume of gas in the bag is then collected onto gold for subsequent analysis.

         3. Collecting a liquid LPG sample in a sample bomb for laboratory analysis.  A sub-sample is then vaporised using a heated pressure regulator and sampled by amalgamation onto gold.

Approaches 1 and 3 are based on the ISO6978 and ASTM 6350 methods for determination of mercury in natural gas.  Approach 2 is described in JLPGA-S-07.  Other sampling methods are also available, including direct injection of a liquid LPG into a GC-AFS system.

There are benefits and challenges associated with each sampling approach.  This poster presents a laboratory comparison of sampling approaches 1-3 with sample determination of mercury by amalgamation-atomic fluorescence spectrometry.

ORAL - The Atomic Fluorescence Spectrometry (AFS) for Element Specific Hg Detection Combined with Combustion

Authors: Dr Warren T Corns (PSA)

The determination of Hg using cold vapour atomic fluorescence spectrometry (CV-AFS) is well established technique that offers low part per detection limits. The CV-AFS approach requires that samples are digested prior to analysis irrespective if the samples are liquids or solids. This is time consuming operation requiring some knowledge of the best digestion approach for particular sample types without introducing losses of Hg or elevated blanks from contaminated reagents. More recently direct combustion in pure oxygen coupled to atomic absorption spectrometry (AAS) with and without gold amalgamation has become commercially available and widely adopted by labs worldwide. A catalyst is typically used to scrub acid gas combustion products to avoid downstream contamination of poisoning of gold trapping systems. In this presentation we will review the analytical performance characteristics of amalgamation AFS when coupled to thermal combustion. Results will be presented for a wide range of environmental, clinical food and industrial samples. Two methods of calibration will be compared including in the injection of saturated Hg vapour from a bell jar at known temperature and aqueous phase calibrations. The system accuracy was validated using certified reference materials.  The presentation will highlight the performance enhancements of AFS compared to AAS.

ORAL - Arsenic Speciation in Water Samples - Development of a new ISO/CEN Method

Authors: Cornelius Brombach, Dr Bin Chen and Dr Warren T Corns (PSA) and Clive Thompson (Alcontrol Laboratories)

A method was developed for the speciation of arsenic in water samples by using HPLC-HG-AFS which is intended for the use as an ISO/CEN technical standard in the future. The four arsenic species arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) can be separated by various mobile phase compositions and the HG-AFS detection makes the method sensitive, cost-effective and element-specific. This presentation will present an overview of the proposed method and will summarize the analytical performance found. One of the keys areas of discussion within the method development working group was in relation to the stability of arsenic species and best methods of sample storage. This is not only an important consideration for the final method but also for inter laboratory collaborative trial preparation. A stability test of different arsenic species in bottled drinking water and seawater was conducted to test the best storage options for arsenic speciation. Three different types of bottles (polyethylene, fluorinated polyethylene and amber polyethylene), two different storage types (fridge or room temperature) and also the effect of acid stabilisation was evaluated.

 

Pittcon 2015

PP078 - Selenium speciation in ruminant livestock feed using liquid chromatography hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS)

Michael R. F. Lee (University of Bristol), Michael R. F. Lee and Hannah R. Fleming (North Wyke, Rothamsted Research) and Dr Bin Chen and Dr  Warren T Corns (PSA)

Se deficiency in dairy cows can cause serious problems such as retained placentas at calving and high somatic cell counts in milk, which in turn reduces milk quality and quantity and increases the risk of mastitis.  Se deficiencies in newly born calves and lambs can result in ill-thrift, brought about by reduced eagerness to suckle milk and white muscle disease. It is therefore common place to supplement for these deficiencies with inorganic minerals such as sodium selenite.  However, ruminants are less able to absorb inorganic Se (<50% absorbed) compared with organic forms. In addition, the inorganic form of Se is less readily converted into milk Se than its organic counterpart. It is therefore important to be able to determine the Se status of ruminant feeds.

It is a challenging task to quantitatively analyse selenium species in livestock feed. Five selenium species have been investigated in this study. The extraction procedure from livestock feed samples and the separation of the five selenium species is investigated and optimised. HG-AFS technical is used for the detection of Se signals with detection limits between 0.13 and 0.43 ng (3s).

To request a copy of this poster click here.

PP079 - Laboratory-scale test systems for mercury, selenium and arsenic adsorbent materials for use in the oil and gas and water treatment industries

Dr Matthew A Dexter, Dr Bin Chen, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Adsorbent materials are widely used in the oil and gas sector to remove mercury from gas and liquid feeds.  Similarly, adsorbent materials are also used in the treatment of waters and waste waters to remove mercury, arsenic and selenium, amongst other contaminants.  The performance of these adsorbent materials varies significantly with the physical and chemical nature of the material itself and with the composition and flow rates of the fluid stream being cleaned.

There is a significant requirement within the industry to test and demonstrate the performance of adsorbent media, from both the suppliers of the media and the end users.  Generation of the required breakthrough curves is time consuming and potentially labour intensive.  The use of a suitable automated test system facilitates the collection of suitable data to demonstrate/test the performance of materials.

Working with standard modules, with bespoke components where required, test bed systems have been developed for a range of applications.  Systems can work with either gaseous, aqueous or hydrocarbon liquid.  In all cases the bed flow rates are precision controlled with mass flow controllers or metering pumps and the media volume recorded.  Analyte concentrations are automatically measured at the inlet, mid-bed and outlet points, with multiple parallel bed streams accommodated to reduce total testing time.  A range of additional criteria can also be met, including wide concentration ranges and addition of other contaminants.

This poster describes bespoke systems for testing adsorbent materials in gaseous, aqueous and hydrocarbon liquid media, presenting breakthrough curve data for various adsorbents.

A copy of this poster will be available in due course.

PP080 - The determination of mercury in unstabilised hydrocarbon liquid streams by vaporisation-amalgamation-atomic fluorescence spectrometry

Dr Matthew A Dexter, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Unstabilised hydrocarbon liquid streams such as unstabilised condensate present particular challenges for sampling and determination.  If the liquid sample is depressurised, a portion of the sample is vaporised, producing a two phase sample for determination.  Mercury can be associated with both the gas and liquid portions of the sample.

Conventionally, determination of liquid process streams which are gas-liquid mixtures when depressurised is difficult due to the need to characterise two separate phases and combine the results.

This poster describes a novel offline auto-injection system designed to introduce the sample to the analyser at process pressure to avoid the issues associated with depressurisation.  Sample is collected into a sample vessel (or “bomb”) at process conditions.  The vessel is then connected to the auto-injection system where it is pressurised with nitrogen to ensure it remains 100% liquid.  A pressurised sample flows through an injection valve, where aliquots of sample are introduced to the vaporisation chamber of a pre-concentration unit, operated in conjunction with an amalgamation-atomic fluorescence spectrometry analyser.

This poster further describes a similar online implementation, using ATEX/IECEx zone 1, certified equipment.  The system can be configured for up to eight sample streams.  Filtered sample is delivered at process pressure to an injection valve, where aliquots of sample are introduced to the vaporisation chamber of a pre-concentration unit and amalgamation AFS analyser.  Both the Pre-concentration unit and analyser are located in purged enclosures.
Results will be presented for demonstrating both the offline and online approaches.

A copy of this poster will be available in due course.

PP081 - Investigation into the Presence of Mercury in Game Controllers

Dr Bin Chen, Dr Warren T Corns and Dr Peter B Stockwell (PSA) and Lee Hewes and Mark Scrimshaw (Brunel University)

The use of game controllers is prevalent with millions of units found worldwide, yet very little research has been conducted into the potential presence of hazardous materials. This study aims to assess the presence of hazardous materials and the potential environmental impact. A preliminary screening involved the dismantling of seven controllers from leading companies within the gaming industry into their individual components before using X-Ray Fluorescence (XRF) which detected mercury in one particular model.  Five further controllers of the same model were purchased and the logos analysed using Scanning Electron Microscope (SEM) in order to provide a secondary qualitative measurement.  Finally samples were analysed using Continuous Flow Vapour Generation Atomic Fluorescence Spectroscopy (CV-AFS). Initial results from XRF demonstrated the presence of mercury in the logo of a specific controller with further analysis of the sample using SEM confirming the initially findings.  CV-AFS was conducted, which produced significant results.  It demonstrated that mercury was present throughout the logo at concentrations at the parts per million levels.  The high level of mercury discovered in the game controllers could pose a significant source of contamination which could have a potentially damaging impact on the environment through the disposal and degradation of materials in the controllers. This research will discuss and highlight game controllers as a novel source of major contaminants, such as mercury, within the environment.  The use of continuous flow vapour generation atomic fluorescence spectroscopy to measure mercury in complex samples will also be discussed and presented.

A copy of this poster will be available in due course.

PP082 - Arsenic Speciation in Food Materials Using Hydride Generation Atomic Fluorescence Spectrometry (HG-AFS) with Automatic Online Solid Phase Extraction (SPE)

Bin Chen, Warren Corns and Peter Stockwell (PSA) and Cornelius Brombach (Aberdeen University)

The adverse health risk of arsenic (As) and its widespread occurrence in the environment as well as in the food chain has raised great public concerns worldwide. Therefore, a routine screening of As concentrations in food materials has become more of an urgent task for food authorities in many countries. It is already well known that speciation, rather than just total As concentration is the key to fully understand the toxicity of As in food products.

HG-AFS offers several advantages for this task such as low cost, high sensitivity and fast analysis. Selective hydride generation atomic fluorescence spectrometry (SHG-AFS) has already been successfully applied to the analysis of inorganic and total arsenic in rice samples with method detection limits (MDL) of 1 and 3 ng g-1, respectively. High performance liquid chromatography (HPLC) together with HG-AFS has also been used to provide the most precise speciation information in food material.

In this presentation, an automatic online SPE approach is demonstrated for arsenic speciation in food materials.  The system is consisting of an autosampler, a 6-port injection valve and a HG-AFS analyser. Sample loop is made of an inline cartridge which contains strong anion exchange packing material. No HPLC was required.  The loading of sample extracts, clean-up of the cartridge, elution and detection of the As species was done automatically using a software package developed in house.  The performance of the system will be discussed in detail in the presentation.

A copy of this poster will be available in due course.

PP083 - Application of the Leaching Environmental Assessment Framework and Vapour Generation Atomic Fluorescence Spectroscopy to Investigate the Fate of Mercury and Arsenic Species after Smouldering Remediation of Contaminated Soils

Christine Switzer, Mara L. Knapp and Andrew Robson (University of Strathclyde) Dr Warren T Corns (PSA) and Rossane C. DeLapp and David S. Kosson (Vanderbilt University)

Smouldering remediation is capable of achieving 99.9+% destruction of coal tar and hydrocarbon contaminants in porous materials. These porous materials experience temperatures in the range of 500-1100°C for periods of minutes or hours depending on contaminant type and operating conditions. Often, contaminated materials contain potentially toxic element (PTE) co-contaminants such as mercury and arsenic. High temperatures and smouldering reactions affect physical and chemical properties of materials subjected to remediation, which, in turn, affect the presence and fate of PTEs in those materials.

The Leaching Environmental Assessment Framework (LEAF) provides a collection of tests, data management tools, and assessment approaches to develop source term release profiles for a wide range of materials. LEAF tests were recently added to the USEPA SW846 compendium as standard methods 1313-1316.

The two materials in this study were a field-obtained soil artificially contaminated with coal tar and a field-obtained made ground from a coal tar contaminated site in the USA. These materials were subjected to smouldering remediation in the laboratory. Mercury and arsenic fate and speciation were studied through the application of cold vapour and hydride generation atomic fluorescence spectroscopy (AFS) in conjunction with LEAF testing and geochemical speciation modelling using LeachXS. Total PTE content seemed to be reduced through volatilisation during remediation. After remediation, changes in soil composition and chemistry affected aqueous release of mercury and arsenic from these soils as well as speciation. This knowledge can be applied to the design of engineering approaches to reduce PTE contaminant levels or availability at contaminated sites.

A copy of this poster will be available in due course.

PP084 - Mercury Speciation by selective pre-concentration and Liquid Chromatography cold vapour atomic fluorescence spectrometry (prec HPLC-CV-AFS) – an efficient method for many sample matrices

Christoph-Cornelius Brombach, Jörg Feldmann and Eva Krupp (University of Aberdeen), Dr Bin Chen and Dr Warren T Corns (PSA)

Mercury is recognized as one of the most toxic elements in nature and its toxicity, bioavailability and transport is dependent on the specie. Organic mercury compounds are known as the most toxic species of mercury and show the highest bioaccumulation.

The concentrations of the species in environmental samples can vary from really low concentrations in water (pg L-1) to high concentrations in predator fish and cetaceans (mg kg-1) and can be challenging for analytical scientists. Speciation in low concentrated samples is nearly impossible with most instrumentation without any preconcentration of the mercury species. In this work, we use an online preconcentration based on the strong interaction of mercury with sulfur compounds and the subsequent separation and analysis via HPLC-CV-AFS.

The method was applied for water samples (e.g. urine, crude sewage, sea water) and MeHg+ was found in spiked samples with recoveries from 91 to 102%. 

Different environmental relevant samples were digested/extracted to different protocols and analyzed with this method: Estuarine sediment ERM® CC-580, various marine materials (e.g. TORT-2, DOLT-4, DORM-2) and hair reference materials. Satisfactory recovery was found ranging from (90 - 105 %).

Additionally, a method comparison was performed with the standard speciation method isotope dilution ID-GC-ICP-MS for rice samples and different tissues of long-finned pilot whales and good correlation coefficients (0.9663 R2 and 0.9728 R2, respectively) obtained.

The developed method requires a minimal amount of sample pretreatment, is low in costs, achieves a LOD of 0.04 ng L-1 for MeHg+ producing reliable and good results.

A copy of this poster will be available in due course.

PP085 - Online Monitoring of Mercury, Selenium and Arsenic in FGD Wastewater Treatment Plants

Dr Warren T Corns and Dr Bin Chen (PSA)

The EPA proposed new rule (40 CFR, part 423) is an attempt to reduce the amount of toxic metals and other pollutants discharged to surface water from power plants. Previous regulations do not consider the additional burden of water discharge pollutants from air pollution control systems such as flue gas de-sulphurization (FGD), selective catalytic reduction (SCR) and flue gas mercury control (FGMC).

The main pollutants of concern include metals (e.g mercury, arsenic and selenium), nitrogen and total dissolved solids (TDS). Toxic metal discharges have a huge impact on the environment as they bio-accumulate in wildlife and cause a wide array of human health issues. The new ruling would establish new and additional requirements for wastewaters associated with FGD wastewater, fly and bottom ash transportation water, flue gas mercury control water, combustion residual leachates from landfill and surface impoundments, metal cleaning wastes and gasification wastewater. Depending on the final options the best available technology (BAT) that is economically achievable will need to be applied to reduce pollutant discharges. This is particularly challenging for dissolved forms of As, Se and Hg as they are not removed by surface impoundments.

PSA have a number of online and laboratory measurement based on AFS and sampling solutions to confirm the efficiency of the wastewater treatment processes and for compliance monitoring. These are outlined with recent experiences and data from the field.

A copy of this poster will be available in due course.

Pittcon 2014

PP070 - Arsenic Speciation in Chinese Medicine by Liquid Chromatography Hydride Generation - AFS

Authors: Hongbin Cao,  Xiancai Zeng (Beijing Normal Uni) Dr Bin Chen, Dr Warren T Corns and Dr Peter Stockwell (PSA)

In spite of the worldwide boom in traditional Chinese herbal medicine (CHM) in recent years, its associated health risks for users due to arsenic and heavy metal contamination, has led to growing public concerns. Arsenic speciation in soils, the effect of arsenic on the growth of various CHM as well as the uptake and accumulation of arsenic in different part of the plant was investigated.  Arsenic concentrations in fresh plant samples can be very low which poses a great challenge for the speciation analysis.  A two-step pre-concentration procedure was proposed in this presentation.  After extraction, DMA, MMA and arsenate in the extract was collected using an anion exchange cartridge.  The residue of the extract was then acidified (pH 2) followed by the addition of APDC.  At this condition, arsenite forms a complex with APDC which was then trapped using a C18 cartridge.  Arsenic species on both cartridges were then eluted using methanol followed by the analysis using LC-HG-AFS.  The proposed procedure not only enables the speciation of arsenic at very low concentration, also greatly reduced the risk of species transformation after the extraction.

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PP071 - Selenium Speciation in Flue Gas Desulfurization (FGD) Wastewater by Ion Chromatography Hydride Generation Atomic Fluorescence Spectrometry (IC-HG-AFS)

Authors: Dr Warren T Corns, Dr Bin Chen and Dr Peter B Stockwell (PSA)

Trace levels of Selenium are present in coal. With tightening regulations on acid gas emissions from coal fired utilities there is an increasing trend to install flue gas desulfurization (FGD) systems. Wet scrubbers based on limestone forced oxidation remove a portion of the Selenium and other volatile metals. The FGD waste water may include particulate and various dissolved forms of Selenium. With regulatory discharge levels typically set to below 10 part per billion (ppb) there is a need to treat FGD wastewater to remove Selenium and also to confirm the effectiveness of the removal process by speciation analysis.  Total selenium in FGD wastewater was analysed using HG-AFS followed by the online UV digestion at elevated temperature.  The samples were also analysed for total selenium using ICP-MS for comparison.  Selenium species in the wastewater was analysed using HPLC-HG-AFS as well as IC-HG-AFS.  Under HPLC separation mode, a citric buffer (pH 5) mobile phase was used which was able to recover selenite and selenate in the sample, while the majority of the selenium in the sample was unable to elute from the column.   Samples were also analysed using IC-HG-AFS under gradient alkaline elution.  Various selenium species including Selenocyanide (SeCN) were found using this method which account for the majority of the total selenium concentration in FGD wastewater.

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PP072 - Industrial Challenges for Calibration of Gas-Phase Mercury Analysers

Authors: Dr Matthew A Dexter, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Traceability of gas-phase mercury analyser calibration is of particular concern with all mercury analysis.  It is important to ensure that the calibration used is appropriate for the sample being analysed, particularly in terms of the species present and, in some cases, the sample matrix.  Elemental mercury calibration is widely available.  In some cases, such as ambient air and coal-fired utility stack monitoring, oxidised sources of mercury are needed for calibration and system integrity tests.

Calibration of mercury analysers used for the automated monitoring of ambient air is frequently in the 0.1-10 ng mass range.  This can be orders of magnitude above the masses collected during air monitoring, with the results measured close to the calibration zero-points, with resulting errors.  Alternative calibration techniques and analyser operations can be adopted to ensure the results are interpolated on the calibration curve.

Suitable calibration strategies can be particularly difficult where transient emissions are monitored, for example waste incinerators or crematoria.  Here a very wide dynamic range is required, with ‘baseline’ emissions at sub-µg/m3 levels and transients at mg/m3 to saturated levels.  To ensure that average emissions are measured accurately, good calibration is required in both of these ranges.  (Inaccurate ‘baseline’ emission results over hours or days can affect the average emissions levels as much as than poorly monitored mg/m3 spikes.)

When used in industrial settings, it is important that analyser calibrations are straight forward and readily understood by the equipment operators.  Analytical considerations can easily be misunderstood or neglected in favour of user convenience, particularly as users are unlikely to have an analytical or scientific background.

This poster will provide an overview of analytical challenges for the calibration of gas-phase mercury analysers, presenting some examples and solutions.

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PP073 - Mercury Release Rates from Dental Amalgam: Measurement and Sampling

Authors: Dr Matthew A Dexter, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

The use of mercury amalgam fillings in modern dentistry continues to cause controversy.  Amalgam fillings are accepted practice in much of the world whilst their use is restricted in others.  Restrictions on the use of amalgam fillings have been advocated on health grounds – the mercury exposure to patients and those preparing, fitting and/or removing being relevant – and on environmental grounds.  One consideration appropriate to this debate is the mercury release rate from amalgam fillings.  The release rate from a dental amalgam surface may be affected by a wide range of factors, including surface area, temperature, consumption of foods and drinks (temperature and chewing) and bruxism.

This poster presents a simple method for measuring the mercury release rate from dental amalgam using amalgamation-atomic fluorescence spectrometry.  Sampling strategies are discussed and data presented showing optimisation of flow rate and sample monitoring.  Mercury release rate data are presented from a self-selected sample of approximately 70 persons.

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PP074 - Mercury Speciation in Canal Sediments by Liquid Chromatography Cold Vapour - AFS

Authors: Mustafa Sharif Ali, Mark Scrimshaw ( Brunel Uni), Dr Bin Chen, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Mercury is a toxic element which is having a negative impact on the environment. Mercury is predominately stored in sediments of various water bodies, but through disturbance it can get into the water and become more accessible to the organisms which bioaccumulates. This particular paper will be concentrating on the Trent and Mersey Canal in Middlewich, Cheshire. A total of 9 cores were taken at 500 meter intervals and each core in turn was sliced into 5 cm sections. The reason why cores were taken instead of grab samples was because this particular Canal experiences high rates of boat traffic in the summer, which disturbs the sediment and allow the more concentrated top soil (0-5 cm) to move downwards where the majority of micro-organisms reside. This will increase the chances of the inorganic mercury being methylated to the more toxic methylmercury. Sediment samples were analysed for total mercury and methylmercury using CV-AFS and HPLC-CV-AFS respectively.  The research aimed to identify and map the mercury and methylmercury contaminations within the sediment.  The methodology used in this study will also be discussed and presented.

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PP075 - A New Modular Approach to Automated Cold Vapour and Hydride Generation AFS for Mercury and Hydride Forming Elements

Authors:  Dr Warren T Corns, Dr Peter B Stockwell and Dr Bin Chen (PSA)

PS Analytical have been manufacturing fully automated cold vapour and hydride generation AFS systems for over thirty years. The determination of mercury and hydride forming elements such As, Se and Sb continues to be a challenging task for many laboratories because of the low levels often encountered. The cold vapour and hydride generation techniques require sample preparation beyond digestion to ensure good hydride and Hg vapour generation yields.  This is because Mercury and the hydride forming elements may occur as organic metallic species and also in different valence states even after sample dissolution. The problem is not unique to vapour generation techniques as the volatility of species may also affect the sample introduction efficiency of ICP systems. Sample preparation is typically done offline prior to measurement which can be time consuming and in some cases detailed knowledge of the species present in the digest is needed. When coupled to liquid chromatography to offer speciation, there is a need to perform post column conversion of eluted species prior to the vapour generation step. 

In this paper we will introduce a new series of modular products based on vapour generation AFS for mercury and the hydride forming elements. One of the modules that will be discussed provides automated sample preparation by use of an UV photolysis system that can operate at elevated temperatures. The system has a built in LC pump and injection valve to provide a compact versatile speciation module. The benefits of this new approach will be discussed with supporting analytical performance data for a new range of products.

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ORAL - Mercury Speciation in Water and Digested Biological Samples by Selective On-line Pre-Concentration and Liquid Chromatography Cold Vapour - AFS

Authors: Christophe-Cornelius Brombach, Eva Krupp, Joerg Feldman (Aberdeen Uni), Dr Bin Chen, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Mercury is among the most toxic elements and the toxicity, bioavailability, and transportation depends on the mercury species. Organic mercury is known as the most toxic species and has a higher bioavailability compared to divalent mercury. Life on earth is based on water and mercury in water ends therefore up in biota. The analysis of water samples for mercury is therefore important but the concentrations of mercury species in natural water are lower than the sensitivity of the analytical methods. The mercury species are therefore pre-concentrated on a pre-column and then eluted using liquid chromatography coupled to UV photolysis and cold vapour fluorescence spectrometry. The method was successfully applied for biological samples (e.g. hair, fish). The advantage of the method is a minimum of sample preparation prior to analysis. The optimisation study and analytical performance will be reported.

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Pittcon 2013

PP065 - The use of Ion Chromatograhy Hydride Generation Atomic Fluorescence Spectrometry (HPLC-HG-AFS) for Arsenic Speciation in Apple Juice

Authors: Dr Bin Chen,  Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Recently, the elevated levels of arsenic found in commercially available apple juice has raised great health concern in the United States as well as other part of the world^i,ii,  The total arsenic levels found in the apple juice tested often reached a high of 36 ng ml^-1. Apple juice as one of the most popular fruit juice in the world is also being used to refine sugar or sweeten other food products.    It is clear that total arsenic concentration cannot be used alone to identify the toxicity of arsenic in apple juice, the information of speciation is imperative in this case. The world production of apple juice is led by China, Poland and Germany.  In this study, a number of apple juice samples sourced in China, Poland, Germany, United States and United Kingdom were analysed for As speciation by IC-HG-AFS.  Apple juice was passed through a C18 cartridge to remove sugar as well as other organic matrix before it was analysed.  No sample digestion procedure was needed.  For speciation, 200 μL of apple juice was injected onto a PRP-X100 anion exchange column.  A carbonate buffer based mobile phase (pH 8) was used to separate all five arsenic species (arsenobetaine, arsenite, DMA, MMA and arsenate).  Baseline separation was achieved within 20 minutes. The analytical performance of both procedures of total and speciation of arsenic will be summarised and compared in detail.

ⁱ Arsenic in Apple Juice, Dr. Oz's Extensive National Investigation - http://www.doctoroz.com/videos/arsenic-apple-juice

ⁱⁱ http://dailynews.sina.com/gb/news/int/int/chinesedaily/20110916/05032772885.html

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PP066 - Online Determination of Mercury in Liquid Hydrocarbon Streams for Process Monitoring and Bespoke Laboratory Test Systems

Authors: C Anthony Rogers, Dr Matthew A Dexter, Dr Warren T Corns, Dr Peter B Stockwell (PSA)

Online analysis of mercury in hydrocarbon streams enables real-time monitoring of the performance of mercury removal systems and enables transient concentration effects to be monitored, which can be particularly important when feedstock sources vary.  Systems based on ISO 6978 and ASTM 6350 are available for the online determination of mercury in gas-phase hydrocarbons, using an amalgamation-atomic fluorescence spectrometry based technique.  The physical state of the petrochemical stream is however a significant complicating factor: the mercury-bearing hydrocarbon sample must be in the gas phase when through the gold collection tube. 

Analysis of liquid hydrocarbon streams has generally involved collection of a sample for laboratory analysis, however collection of representative offline samples can be difficult, especially when the sample is a liquid:gas mixture at atmospheric pressure. Collection of the depressurized sample is problematic as volatile elemental may be lost from the sample.

This paper describes the online implementation of an amalgamation-atomic fluorescence-based technique for the online determination of mercury in liquid hydrocarbons in two different scenarios:

1. Online monitoring of an MRU outlet stream, where the process stream is a liquid at process conditions but a liquid-gas mixture at atmospheric pressure.  The analyser is located in an Ex p cabinet for installation in a hazardous area, close to sample take off point.  Sampling occurs at process pressure to ensure that the sample remains in the liquid phase.

2. A bespoke system for the online testing of materials susceptibility to mercury in liquid hydrocarbon streams.  In addition to a multi-stream liquid hydrocarbon analyser, the system includes the material test beds, mercury in liquid hydrocarbon source, metered pumps to control the flow over the test beds.

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PP067 - Pre-concentration of Mercury for Speciation via HPLC-CV-AFS

Authors: Christophe-Cornelius Brombach, Eva Krupp, Joerg Feldman (Aberdeen Uni), Dr Warren T Corns, Dr Bin Chen, Dr Peter Stockwell (PSA)

The analysis of mercury species in the aquatic environment is of extreme importance to understand the fate and transportation of mercury. The toxicity of Mercury is known to be dependent on the chemical form and organic mercury species are generally more toxic. The low concentration of mercury species in natural water is an analytical challenge and large volumes of samples need to be processed. The transportation of samples can be problematic as Hg species are relatively unstable and preservation methods may alter speciation. To overcome these issues we have explored solid phase extraction techniques using micro-columns to selectively enrich mercury species from natural water samples. The main advantage of this approach is that the procedure can be done in the field overcoming the problem of sample storage and transportation. Alternatively the procedure can be performed in the laboratory using an automated approach. On elution, the mercury species are separated using liquid chromatography coupled to UV photolyis and cold vapour atomic fluorescence spectrometry. The optimisation study and analytical performance of this approach will be reported.

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PP068 - Mercury in Skin Whitening Creams

Authors: Reeya K Oogarah, Jasmina Allen and Dr Warren Corns (PSA)

Mercury has no biological function in humans. It is a toxic metal and its harmfulness has been known since ancient times.  Mercury can be found in cosmetic products especially in skin whitening creams, which are used primarily for beauty treatment purposes. The active ingredients of these creams are rarely reported on the packaging of these products and as a result the user may unknowingly be at risk of Hg exposure. The United Kingdom laws ban skin whitening creams containing mercury while the United States Food and Drug Administration specifies that these creams contain less than 1 ppm of mercury.

The development of a method to determine the mercury content in a variety of skin whitening creams using cold vapour atomic fluorescence spectrometry (CV-AFS) will be reported. Analytical performance data will be presented.

Nine skin whitening creams bought locally and internationally were analysed. No information about the mercury content in the creams was presented at the time of purchase. The method used for digestion comprised of aqua regia treatment of the samples on a hot block prior to analysis. The mercury content in four of the nine creams was less than the method limit of detection (2ppb).  Two creams had between 71 and 315 ppb of mercury whilst the remaining three creams had between 3 to 13,120 ppm.

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ORAL - Arsenic Speciation in Rice using Atomic Fluorescence Spectrometry with a Focus on i-As in Rice

Dr Bin Chen, Dr Warren T Corns(PSA) and Jen-How Huang (Institute of Biogeochemistry and Pollutant Dynamics)

The adverse health risk of arsenic and its wide spread in the environment as well as in the food chain has raised great concern in the public worldwide. A routine screening of arsenic content in food products has become more of an urgent task for food authorities in many countries. Recently, a simple extraction procedure based on hot dilute nitric acid was developed to quantitatively recover arsenical species from rice grains without the risk of specie transformation (Huang et al1). However, the use of inductively coupled plasma mass spectrometry (ICP-MS) in Huang et al. is relatively expensive and may not be feasible for analysis of large amounts of samples. On the other hand, the incomplete digestion of rice grain will result in C-rich matrix, which may potentially affect ICP-MS detection of As. Thus, the objective of this study is to develop and verify the methodology of arsenic speciation in rice grains based on hydride generation atomic fluorescence spectrometry (HG-AFS) after ion chromatography separation.  A total number of 80 rice samples of different types were collected around the world. Baseline separation of arsenite, dimethylarsinic acid, monomethylarsonic acid and arsenate were achieved on a strong anion exchange column (PRP X-100) isocratically using a mobile phase of phosphate buffer at pH 6.2. The analytical performance of both detection techniques of HG-AFS and ICP-MS will be summarised and compared in detail.

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Pittcon 2012

PP061 - Automated Digestions to determine Total Mercury using Cold Vapour Atomic Fluorescence Spectrometry

Authors: Dr Warren T Corns, Dr Bin Chen, Jasmina Allen (PSA) Christoph Cornelius Brombach, Eva Krupp and Joerg Feldman (Aberdeen Uni)

Cold vapour atomic fluorescence spectrometry is a well technique to determine mercury in a wide range of samples. Tin (II) chloride is the traditional reduction used to convert divalent mercury to elemental mercury. Prior to analysis all samples require digestion to convert all Hg species to divalent mercury. Manual digestion methods are time consuming and also are prone to Hg contamination. In this paper will be describe a newly developed UV photolysis system used in combination with various acid oxidant mixtures. A detailed optimization study will be presented to maximize the analytical performance of the system. The automated digestion method will be fully validated and a comparison will be made between manual and automated digestion for a wide range of water samples.

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PP062 - Field Comparison of Manual and Semi-Automatic Methods for the Measurement of Total Gaseous Mercury in Ambient Air and Assessment of Equivalence

Authors: Dr Matthew A. Dexter, Dr Warren T. Corns (PSA), Richard J. C. Brown*, Yarshini Kumar, Andrew S. Brown (NPL)

The manual and semi-automatic methods for the measurement of total gaseous mercury in ambient air have been compared in a field trial for the first time.  The comparison results have shown that whilst the expected random scatter is present, there was no significant systematic bias between the two methods, whose operational differences have also been outlined and analysed in this work.  Furthermore it has been observed that because variation in instrument sensitivity is largely random in nature there is little effect on the results of the comparison if the period between instrument calibrations is altered.  When the manual and semi-automatic methods are compared according to guidelines produced by the European Commission the results presented here, taken together with other supporting evidence, strongly suggest that the two methods are equivalent.

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PP063 - Mercury in workroom Air Monitoring using AFS

Authors: Dr Matt Dexter, Dr Warren Corns and Tony Rogers (PSA)

The toxicological effects and hazards of mercury are well known.   Mercury may be inhaled from various sources including mercury vapour, particulates containing mercury and also organic mercury. Occupational exposure limits for mercury vary depending on the International Authority and the type of mercury exposure. The Health and Safety Executive (HSE) currently has a long term exposure limit of 25µg/m3 for an 8 hour time weighted average reference period for mercury and its inorganic divalent compounds.  Companies that use mercury in their production process or have mercury vapour as a contaminant have an obligation to monitor the exposure to their employees to ensure that the exposure limit is not exceeded.  This is typically achieved using passive diffusion badges or by drawing a sample across a sorbent tube. At the end of the exposure period the sorbent material is digested with an equal mixture of HCl and HNO3 and the mercury is then determined by CV-AFS. The analytical performance data using this method will be presented along with typical data for an occupational exposure study. An alternative method using gold amalgamation coupled to atomic fluorescence spectrometry will be described and applied to offline and multiple stream online applications.

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PP064 - Determination of Antimony Species in Food and Hair Samples using LC-Hydride Generation Atomic Fluorescence Spectrometry

Authors: Dr Bin Chen, Dr Warren T Corns (PSA), Fengchang Wu, Zhiyou Fu, Bijun Liu, Changli Mo and Haiqing Liao (State Key Laboratory of Environmental Criteria and Risk Assessment)

Recent studies have shown that antimony is a Pollutant of global concern because of its high toxicity to humans and its role in causing diseases of the liver, skin, respiratory and cardiovascular systems. The joint food and Agricultural Organization (FAO)/World Health Organization (WHO) Expert Committee on Food Additives has not evaluated the safety of Sb. The USEPA however has provided an oral reference dose of 0.4µg/Kg body weight per day and there is also a much higher level cited by the WHO water quality guideline of 6µg/Kg body weight per day. Although the general population is not considered to be at risk certain regions such as those living in the vicinity of smelters and mining areas are likely to be more exposed to not only to antimony and also Arsenic. The largest production of Sb is China accounting for 80% of global requirements with the largest mine being the Xikunuangshan Mine in central China. In this area there are high background levels of Sb and As in soils and a large percentage of local residents and miners have acute arsenic poisoning and antimony dermatitis. To date the health risk of human exposure for people in this area has not been fully evaluated.

In this paper hair and food samples from residents in this region were analysed for Antimony speciation using HPLC-hydride generation atomic fluorescence spectrometry. Sb species were separated by an Hamilton PRP X100 strong anion exchange column using a mobile phase of 200mmol/l ammonium tartrate. Fish samples were found to contain Sb(III) as the dominant species whereas vegetables and drinking water was found to be Sb(V). Hair samples of local residents had an average of 64% Sb(V) and 36% Sb(III). A summary of the analytical techniques being used to study the health risks associated with dietary exposure to Sb in this mining area.  

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Pittcon 2011

PP052 - Speciation of Inorganic Arsenic in Food by Hydride Generation Anion Exchange Liquid Chromatography Atomic fluorescence Spectrometry with Online Ultraviolet (UV) Digestion (HG-LC-UV-AFS)

Dr Bin Chen, Dr Warren T Corns and Dr Peter B Stockwell (PSA) and Jitesh S. Thakur (Loughborough Uni)

The occurrence of inorganic arsenic in food has received worldwide concern during recent years due to its toxicity and adverse health effects.  It is known to be human carcinogen and can cause skin and bladder cancer.  Inorganic arsenic (arsenite and arsenate) are not only commonly found in the groundwater, they are also found to be the predominant species in some food such as rice.  Reliably monitoring inorganic arsenic levels in food samples are one of the most urgent task in order to assess its impact on human health.

Several extraction methods have been developed for the extraction of arsenic species from food samples, especially in rice.  A nitric acid based extraction method was found to be most suitable in that DMA, MMA and arsenobetaine remain untouched in the media.  Inorganic arsenic is then quantified as As(V).  The proposed procedure quantitatively recovers the most common arsenic species such as inorganic arsenic, DMA, MMA and arsenobetaine.  The speciation analysis of the above mentioned species was based on an anion-exchange liquid chromatography coupled with hydride generation atomic fluorescence spectrometry with online UV digestion of the methylated and organic As species.  A reference material (NIST SRM 1568a rice flour) was used for the quantification and speciation.  Recoveries of inorganic arsenic and DMA were found to be nearly 100%.

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PP053 - Antimony Speciation in Sweeteners Using Liquid Chromatography Hydride Generation Atomic Fluorescence Spectrometry (HPLC -HGAFS)

Dr Bin Chen, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Antimony and its compounds have no known biological role, are nearly as toxic as lead and have been listed as priority pollutants by the US EPA, Council of the European Union (EU) and German Research Community (DFG).  Elevated level of Sb was found in various brands of sweeteners in the market which again raise the concern of its impact on human health.  Total antimony and its speciation in sweeteners have been carried out using atomic fluorescence spectrometry.  Antimony (III) and (V) was separated and quantified by an anion exchange column with a mobile phase containing 200mM ammonium tartrate at pH 5.  The majority of Sb in sweeteners was found to be the more toxic Sb(III). 

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PP054 - Online Determination of Mercury in Sour Natural Gas Streams

Authors: Dr Matthew A Dexter, C Anthony Rogers, Dr Warren T Corns and Peter B Stockwell (PSA)

Accurate determination of mercury in petrochemical streams is important for environmental and operational/safety reasons.  Mercury damage to petrochemical plant can lead to long downtime and high costs, both in replacement parts and due to lost production.  Mercury has caused corrosion and in some cases failure of aluminium components including heat exchangers, rotors and condensers.  Mercury has also been shown to be responsible deactivation of palladium hydrogenation catalysts which are commonly used for selective hydrogenation of alkynes in the C2 to C4 fraction.

Online determination of mercury in natural gas streams is used to confirm correct operation of activated carbon or precious metal-based mercury removal units (MRUs) or to confirm mercury levels of product streams are within specification.  Whilst these measurements are themselves non-trivial, they can be far more difficult when the petrochemical source is contaminated as in some areas by high levels of hydrogen sulfide. These sour gas streams may contain levels of H2S from 4 ppm to >20 % hydrogen sulfide.  Determination of mercury in the sour gas streams is therefore necessary to ensure the continuance of the production process.

This poster presents an amalgamation-atomic fluorescence spectrometry-based online analyser for the determination of mercury in sour gas.  The instrument is based on PSA’s long established range of online and offline mercury in natural gas instrumentation.  Data will be presented confirming the efficacy of the technique in sour gas containing up to 18 % hydrogen sulfide.

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PP055 - Online Measurements of Arsenic and Mercury Using Atomic Fluorescence Spectrometry

Dr Bin Chen, Dr Matthew A Dexter, Dr Warren T Corns and Dr Peter B Stockwell

Given the challenging legislative framework, many of our customers operate in, it is essential that any in-process As or Hg analyser gives the security of complete compliance yet and also has the flexibility to meet future regulatory requirements.  The online analyser described in this work provides just that security through a unique combination of continuous As or Hg measurement, custom chemistry and the inherent sensitivity of atomic fluorescence detection, all with the additional benefit of low operator intervention saving time and money.  The authors believe that the recently developed As online liquid instrument is the first instrument of its kind worldwide.

Designed and manufactured for long-term stability in hostile environments, the online analyser introduces a number of novel features which combine the convenience of laboratory based systems with the ease of use demanded by process analysis.  In addition, a comprehensive user friendly software package for data acquisition, statistical analysis, reporting and display is described. The software performs real time calculation and presentation of the analyte content for each process concerned. The software can be readily customised to suit individual needs for monitoring and reporting.

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PP056 - Mercury Speciation and Total Mercury in Fish and Seafood Products

Authors: Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Mercury has long been the focus of attention since the early tuna fish scares in Japanese diets. The form of the mercury is of considerable importance and the ability of the analysts to measure these reliably requires sensitive and accurate methodology and measurements. Atomic Fluorescence Spectrometry provides the measurement tool and examples of its coupling to a range of chromatographic techniques will be described.

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Pittcon 2010

PP046 - The Development of International Standards for the Sub ppb Determination of Hydride Forming Elements in Water Samples using AAS and AFS.

Authors: Dr Warren T Corns, Dr Peter B Stockwell and Jasmina Allen (PSA)

This paper will focus on the methodology for the hydride generation of As, Sb and Se prior to measurement using AAS and AFS.  Data from a series of International ISO Interlaboratory trials undertaken by seventeen laboratories will be presented. 

Analytical performance data from the participating laboratories will be critically evaluated and discussed.

The benefits of atomic fluorescence and atomic absorption will be compared.

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PP047 - Rapid Arsenic Speciation Analysis in Water Samples using Flow Injection Hydride Generation Atomic Fluorescence Spectrometry with a Low Pressure Short Column

Authors: Dr Bin Chen, Dr Warren T Corns, Jasmina Allen, and Dr Peter B Stockwell (PSA)

Inorganic arsenic (arsenite and arsenate) are the most common arsenic species found in water samples.  They are proven to be carcinogenic due to their much higher toxicity than organic arsenic forms.  Fast and accurate screening of inorganic arsenic species in water samples has increasingly received great attention.  Arsenic generally presents in water samples at low ng/ml levels, and the transformation between arsenite and arsenate can also be troublesome during the sample collection and transportation processes.  In this presentation, a fast, easy yet accurate sampling method and sensitive analysis protocol is proposed for arsenic speciation in water samples.

Two cartridges (A and B) were used to collect water samples for arsenic speciation.  An aliquot of the water sample (100 ml) was passed through cartridge A or B.  Cartridge A is packed with a modified C8 absorbent which only retains arsenite, and cartridge B is packed with anion exchange material which only retains arsenate.  Samples were collected on these cartridges on site and subsequently shipped to the lab.  Cartridges not only pre-concentrate arsenic in the water samples, but also avoid the inter-specie transformation.  Upon receipt of the sample in the lab, 10 ml of 25 % (v/v) HCl was passed through the cartridge and the arsenite or arsenate was eluted.  The eluent was then pre-reduced by the addition of 2% KI (m/v) prior to the analysis by hydride generation – atomic fluorescence spectrometry.  This procedure greatly reduces the risk of specie transformation, as well as increasing the precision and sensitivity of the analysis.

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PP048 - The Origins of the ‘Dumarey Equation’ Describing the Saturated Mass Concentration of Mercury Vapour in Air

Authors: Ronny Dumarey (Gent), Richard J Brown, Andrew S. Brown (NPL), Dr Warren T Corns, Dr Peter B Stockwell (PSA)

Mercury has been recognised as an environmental air pollutant for many years. Usually analyses are carried out by cold vapour amalgamation coupled to atomic spectrometry techniques with a calibration based on injection of air saturated with mercury vapour. All these measurements are ultimately traceable to the saturated mass concentration of mercury in air at a given temperature, as this relationship underpins the calibration procedure.

The saturated mass concentration of mercury vapour in air is given indirectly via the ideal gas law by a variety of empirical equations describing the vapour pressure of mercury.  Recent work to develop a standardized European method for the measurement of mercury vapour in air has brought into sharp focus the requirement to define the most suitable relationship for the saturated mass concentration of mercury in air. 

The ‘Dumarey equation’ has been the dominant relationship used to calculate the saturated mass concentration of mercury vapour in air for over 25 years.   However, the origin of the equation and the validation data supporting its accuracy has never been published.  We now address that deficiency and compare the Dumarey equation with other data sets [1] to which it has been wrongly attributed in the past, and describe why it remains superior to the use of mercury vapour pressure data in combination with the ideal gas law.

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PP049 - Online Process Analysis of Mercury in Petrochemical Streams

Authors: Dr Warren T Corns, Dr Peter Stockwell and Dave Vickery (PSA)

Knowledge of the mercury content in petrochemicals is extremely important.  Firstly, mercury is highly toxic and is of environmental concern and secondly, the damage caused to petrochemical plants can be financially crippling especially when unscheduled shutdowns are forced.  Mercury has been found to be responsible for many cases of selective hydrogenation catalyst deactivation.  Palladium based catalysts are commonly used for the selective hydrogenation of alkynes in the steam cracking of C2 to C4 cuts.  Mercury is known to be the cause of corrosion problems with alumina-based heat exchangers, rotors and condensers at natural gas refinery plants.  Heat exchanger replacement is a costly operation due to the capital investment of the exchanger itself and the plant down time incurred for its replacement.  This paper describes how atomic fluorescence spectrometry (AFS) can be applied to the measurement of mercury in petrochemical samples such as natural gas, LPG, LNG, naphtha and condensates.   Typically these measurements are performed using offline laboratory techniques which are highly dependent on the sampling protocols utilized and the sample storage method. This is especially problematic for volatile forms of Hg which are easily lost from the sample. We have recently developed online process analyzers for both liquid and gaseous petrochemical streams. These are typically used in conjunction with mercury removal technologies so that the efficiency can be monitored in real time thus protecting expensive downstream apparatus. The performance characteristics of the analyzers will be discussed with reference to sampling, calibration, accuracy, precision and long term reliability.

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ORAL - Speciation of Mercury in Hair using GC-AFS and HPLC-UV-CV-AFS

Authors: Dr Warren T Corns, Dr Peter Stockwell, Dr Bin Chen, Jasmina Allen and Pritam Kundoo (PSA)

The use of atomic fluorescence spectrometry (AFS) coupled to gas and liquid chromatography has been used for mercury speciation measurements for a number of years. The major routes of human exposure to mercury is via inhalation of mercury vapour as Hg0 from sources such as dental amalgams and occupational exposure, consumption of fish products as CH3Hg+ and also from vaccines which contain the Thiomersal preservative CH3CH2Hg+ (known in the US as Thimerosal).

Different mercury species have varying toxicological effects and also different routes of detoxification. Total mercury in hair for a non exposed person is typically in the range of 0.4 to 6.0mg/g which is several 100 times higher than the level typically found in blood. It has been reported[1] that the mercury in first cut baby hair from children with Autism is significantly lower suggesting that they have an inability to excrete mercury from their system. The excretion mechanism is not fully understood at this time and therefore there is a need for reliable methods to determine Hg speciation in hair samples.

This paper will compare different analytical extraction methods and their suitability for liquid and gas chromatography coupled to AFS. Data will be presented for a wide range of hair samples and comparisons made for different exposure groups.

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Pittcon 2009

PP042 - A Practical Uncertainty Budget for Ambient Mercury Vapour Measurement

Authors: Richard J C Brown, Andrew S Brown, Rachel E Yardley (NPL), Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Measurements of mercury in ambient air are assuming greater importance, because of increasing health concerns and legislation in Europe and elsewhere.  In order to have confidence in the measured values and to assess compliance with values, measurements must be made using validated methodologies which have traceable uncertainty statements associated with them.  A practical uncertainty budget for the measurement of vapour-phase mercury in ambient air, sampling onto a gold-coated silica adsorption tube and measuring with atomic fluorescence spectrometry will be discussed.  Moreover, this budget may be generalised for other related measurement methods for mercury vapour and other ambient air pollutants.  All significant sources of uncertainty will be discussed and estimated.  The expanded relative uncertainties at the 95% confidence interval is approximately 17%.  These are estimated for exemplar measurements made by the National Physical Laboratory (NPL) as part of the UK Heavy Metals Monitoring Network.

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PP041 - Mercury in Crematoria using Atomic Fluorescence Spectrometry

Authors: Dr Warren T Corns, Dr Peter B Stockwell and Dr Matthew A Dexter (PSA)

The fate of mercury in the environment continues to cause concerns and legislation in Europe is now focussing attention on the mercury emission levels from crematoria.  Several manufacturers of Crematoria are designing abatement systems to control the mercury levels emitted. This is not a simple problem, because the mercury levels are not consistent and can reach higher levels that cause concern.  In addition to abatement, the legislation will require measurements and reporting the levels of emission.

The P S Analytical range of atomic fluorescence instruments, particularly the Sir Galahad, provide an ideal facilitator to both act as a control mechanism and to provide reliable measurement data suitable for regulatory purposes.  Several abatement technologies are currently being developed and the PSA atomic fluorescence spectrometer provides these with the necessary facilities to evaluate the technologies and to fine tune their performance for this emissions requirement.

Examples of the technologies developed and their interaction with the atomic fluorescence measurements will be described.

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PP040 - Speciation of Selenium in Industrial Samples using HPLC-UV-HG-AFS

Authors: Dr Bin Chen, Jasmina Allen and Dr Peter B Stockwell (PSA)

Selenium has a dual role in the human body, both as a toxicant and an essential trace element at different concentrations.  Selenium can be presented in both inorganic (selenite, selenate, hydrogen selenide etc) and organic forms (selenomethionine, selenocysteine and selenoproteins etc). Among them, hydrogen selenide is extremely toxic while selenomethionine is essential and nutritional to the human body.  The forms and the concentrations of selenium define its role in the environment and in the living systems.  The field of selenium speciation has been receiving increasing attention over the past decades. Research and routine analysis of selenium is undertaken in waters, plants, soils, nutritional supplements, biological samples (urine etc.) and industrial effluent or waste water samples in many environmental institutions and agencies.

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Pittcon 2008

PP035 - Determination of Total Gaseous Mercury in Ambient Air using Amalgamation Coupled to Atomic Fluorescence Spectrometry

Authors: Dr Peter B Stockwell and Dr Warren T Corns (PSA)

Measurements of mercury in ambient air are assuming greater importance, because of increasing health concerns and legislative requirements. The general public and the environment can be exposed to mercury originating from natural, domestic or industrial processes. Coal-burning power plants are the largest anthropogenic source of mercury emissions to the air.  Burning hazardous wastes, the chlor-alkali industry, crematoria, breaking mercury products, and spilling mercury, as well as the improper treatment and disposal of products or wastes containing mercury, can also release it into the environment.

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PP034 - Field Experience of a Mercury Continuous Emission Monitoring System

Authors: Dr Matthew A Dexter, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

The Clean Air Mercury Rule provides a regulatory regime for the control of mercury emissions from coal-fired utilities in the United States.  The rule requires the installation of continuous emission monitoring systems at the majority of such utilities and provides a detailed regime of tests to validate data from the emissions monitoring system.  Elemental and oxidised mercury calibration gases traceable to national standards are required for the validation tests.

The P S Analytical Continuous Emission Monitoring System has been used to monitor gas-phase mercury concentrations in coal-fired utility stack gas.  The instrument consists of a sampling probe, heated sample transfer line, sample conditioning system, analyser and calibration modules. 

The sampling probe extracts sample from the stack, separates the gaseous sample from fly ash, and delivers the diluted sample to the sample conditioner via the heated sample line.  The sample is conditioned to convert all mercury in the sample to elemental mercury and is delivered to the analyser without the need for water injection.  Mercury in the sample is determined by amalgamation coupled with atomic fluorescence in the Sir Galahad Analyser, providing a method detection limit of less than 0.01 µg m-3.

A calibration gas generator and delivery manifold system is incorporated to deliver known-concentration calibration gases to the sampling system for system integrity validation tests.

The various components of the PSA Hg CEM will be described and results of recent field experience of the system and compliance with the regulatory tests will be presented.

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PP033 - Using the PSA Millennium Excalibur System for the Speciation of Arsenic and Selenium Metabolites in Human Urine

Authors: Dr Bin Chen, Tessy A Momoh, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Arsenic and its compounds are known to cause several adverse health effects. Selenium behaves a dual role in human body both as toxicant and essential trace element at different concentration and the difference of the concentrations are very small. Because urine is a major excretory route for both As and Se, urinary As and Se metabolites were used recently in epidemiological and environmental health studies as a means of assessing exposure to As and Se from various sources. The concentrations of urinary As and Se methylation are often found low enough (~ ng/ml) which require sensitive analytical methods involving speciation, identification and quantification of each individual species. Using Millennium Excalibur system based on high performance liquid chromatography coupled with hydride generation atomic fluorescence spectroscopy (HPLC-HG-AFS), As metabolites such as arsenobetaine, arsenite, dimethylarsenic acid, monomethylarsonic acid and arsenate, and Se metabolites such as selenosugar, selenite, selenate, selenomethionine, selenoethionine  have been separated using ion-pairing reverse phase HPLC within 10 and 15 minutes for As and Se, respectively.  A mobile phase of pH 9 containing 20mM ammonium phosphate, 5mM TBAH and 4% ethanol was used for As speciation, and a mobile phase of pH 4 containing 30mM Ammonium Formate, 1% methanol, and 0.01mM DDAB. The eluent was further digested using an online post column UV digestion device at 200 °C, followed by the sensitive detection of HGAFS which was able to provide detection limits of 0.4-0.8 ng/ml for all the As and Se species. The developed methods provided sensitive, robust approaches for the monitoring of As and Se methylations in human urine samples.

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PP032 - Performing EPA Methods 245.7 and 1631 utilizing the PSA Millennium Merlin System

Authors: Dr Bin Chen, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Mercury is naturally present in aquatic systems in very low concentrations. Due to the long range atmospheric transport and deposition of anthropogenic mercury, elevated concentrations of mercury are found even in remote freshwater system although no direct local contamination sources are present. It is long recognised that mercury is one of the most hazardous toxicant to human and the environment. To protect people and the environment from the mercury, governments and regulatory agencies are introducing ever more stringent guidelines. As a result, analysts are challenged to achieve the ever greater sensitivity. The USEPA approved Method 245.7 and Method 1631 for the determination of low level total mercury in water. Both methods are based on vapor generation atomic fluorescence spectrometry (CV-AFS). In this work, a comparison between performing these two EPA methods with PSA Millennium Merlin system is presented. The methodology, operation procedure, analytical sensitivity, and the quality control criteria are compared in detail.

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Pittcon 2007

PP028 - Determination of Mercury Species in Portuguese Salt Marshes using Capillary GC - Atomic Fluorescence Spectrometry

Authors: Dr Warren T Corns, Dr Peter B Stockwell Dr Derek Bryce (PSA), M Valega, E Pereira (Uni Aveiro) and M Pardal (Uni Coimbra)

Salt marshes located near by industrialised areas can act as natural sinks for trace metals. Anthropogenic metals, associated with suspended particulate matter can be transported by tidal currents and trapped by vegetation with subsequent incorporation into sediments. Plant roots can interact with the surrounding sediment, exuding oxygen and organic compounds that influence the distribution and availability of trace metals; however, the amount of metals taken up by the plants is dependent of the metal availability in the sediment, and this is modified by the root activity. Oxygenation of upper estuarine sediments decreases rapidly with depth due to the consumption of oxygen in the oxidation process of the organic matter; however, salt marsh sediments receive an additional input of oxygen in the sub-surface layers through the well developed aerenchyma of salt marsh plants (halophytes) which transports oxygen from leaves to roots and consequently to the surrounding sediments. This supply of oxygen can alter significantly the redox status of sediments with strong repercussions on the biogeochemistry of nutrients and trace elements, namely mercury. The methylation of mercury in salt marsh sediments is poorly documented, although abundant micro-organisms and strong redox gradients between roots and surrounding sediments may favour that process. Because the sediment environment in salt marshes is exceedingly complicated it is pertinent to investigate the conversion of inorganic mercury into organomercury species. A fully automated GC coupled to atomic fluorescence spectrometer will be described for the determination of methylmercury in sediments and salt marsh plants.

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PP027 - Determination of Heavy Metals in Produced Water and Driling Discharges using Atomic Fluorescence Spectrometry

Authors: Dr Warren T Corns and Dr Peter B Stockwell (PSA)

During the extraction of oil and gas a large quantity of undesirable water and drilling waste is produced.  The chemical composition of discharged wastes is complex and may vary at different stages of oil and gas production.  Drilling mud formulations have varied greatly over the years and are also dependent on the rock formation to be drilled.  Barite (BaSO4) is commonly used in water based drilling mud to control and regulate the hydrostatic pressure in the well.  This material contains high levels of heavy metals such as mercury, arsenic, selenium, lead, cadmium, zinc, copper, chromium and others.  The cuttings of the drilling process are typically discharged to the environment giving cause for concern to marine wildlife. .  The environmental effect of heavy metals from drilling discharges has created much debate.  Barite and associated trace minerals are of a non soluble form and are therefore believed by many not to be bio-chemically available to marine organisms.

This paper will discuss the analytical methods that can be used for determinations of heavy metals from drilling mud, discharges, produced water, marine sediments and water.  The paper will focus on the use of vapor generation - atomic fluorescence spectrometry (AFS) as a method for determining mercury, arsenic, selenium and antimony. This approach has been coupled to HPLC separation techniques to provide speciation measurements.  A fingerprinting method using the trace metals of Barite will be presented that potentially can be used to monitor the fate and distribution of heavy metals from drilling discharges.

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PP026 - Arsenic Speciation in Atmospheric Total Suspended Particles using Atomic Fluorescence Spectrometry

Authors: Dr Warren T Corns, Dr Peter B Stockwell (PSA), V Oliveira, J L Gomez-Ariza and D Sanchez-Rodas (Uni Huelva)

An arsenic speciation study was performed using air filters on which total suspended particles (TSP) were collected from the city of Huelva, a medium size city with huge industrial influence in SW Spain. Different extraction procedures were performed using water, NH2OH.HCl and H3PO4 solutions with either microwave or ultrasonic radiation. The optimal extraction procedures were found to be with the use of 100 mmol L-1 NH2OH.HCl and 10 mmol L-1 H3PO4 with microwave radiation for 4 minutes. High Performance Liquid Chromatography coupled with hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS) was employed for the determination of arsenic species. The average extraction efficiency for air filters collected on a monthly basis (n=12) was found to be 94% and 86% with NH2OH.HCl and H3PO4 respectively. Only inorganic arsenic species (arsenite and arsenate) were detected. The annual mean arsenite and arsenate concentrations were found to be 1.2 +/- 0.3 ng m-3 and 10.4 +/- 1.8 ng m-3 respectively. Arsenate levels were found to be more variable with maximum concentrations reaching 30.6 ng m-3.The high level of arsenic species in the TSP samples can be related to a copper smelter located in the region.

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PP025 - Calibrating Mercry CEM Instrumentation

Authors: Dr Warren T Corns, Dr Peter B Stockwell, Dr Derek Bryce and Dr Matthew A Dexter (PSA)

The Clean Air Rule has provided the legislation for the regulation and control of mercury emissions from coal fired utilities in North America.  To ensure the integrity of the systems designed to measure the mercury levels emitted it is essential to develop suitable calibration sources which are traceable to national standards be it the National Institute of Standards and Technology or other national standards bodies.  

Since the introduction of its first mercury continuous emissions monitor P S Analytical has provided a calibration source the CAVKIT, which allows a set concentration of mercury to be introduced at various stages in the sampling and measurement cycle.  This has been successfully used to check calibration and to test the integrity of the full system.  The system has been evaluated by NIST.  Further developments to provide a source of oxidised mercury will be described and the experience of this in this in the field will be described.

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Pittcon 2006

PP024 - Development and Applications of an Online Calibration System for Mercury Analysers

Authors: Dr Warren T Corns, Dr Peter B Stockwell and Dr Matthew A Dexter (PSA)

With an increasing need to measure mercury in gaseous samples using online Hg analysers an automated calibration system has been developed.  Traditionally permeation tube devices have been used for this purpose however these suffer from poor accuracy, limited concentration range and long stabilization times. Hg in nitrogen calibrations gas cylinders are available but these are expensive and have short shelf-lives.  To overcome these issues a simple yet effective device has been developed based on the dilution of a Hg0 saturated vapour at known temperature.  The system developed uses two NIST traceable mass flow controllers to deliver accurate flow rates.  A low flow of gas, between 1 and 20 ml min-1, was passed over a Hg reservoir located in a temperature calibrated oven.  This gas becomes saturated with Hg vapour.  The saturated gas is mixed with a diluent gas flow supplied by the second mass flow controller to achieve the concentration range of interest.  By varying temperature and flow rates the device offers a wide range of concentrations in the ng m-3 and µg m-3 regions. 

Currently, no NIST traceable or NIST certified gas-phase mercury standards are available, although studies for the EPA have shown similar uncertainties for the output of calibration gas generator described here and for Hg in N2­ standard cylinders.

Applications will be described where the calibration system has been used for mercury measurements in flue gas from coal fired power stations.

US EPA performance specification 12A requires mercury continuous emissions monitors to be challenged with both elemental and oxidized mercury standards.  Results will also be presented for an oxidised mercury source developed for this purpose.  Saturated mercury (II) chloride vapor was generated by passing a low flow of carrier gas over an isothermal bed of HgCl2.  This vapor is then diluted into a carrier stream to produce the desired concentration of oxidised mercury.  The accuracy of the technique compared to theoretical values based on vapor pressure concentration will be demonstrated.

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PP023 - Determination of Mercury Levels in Liquid Hydrocarbons: Can We Achieve a Mass Balance with the Procedures already in place?

Authors: Dr Peter B Stockwell and Dr Warren T Corns (PSA)

With the introduction of Atomic Fluorescence Spectrometry we have the tools with the potential to reach the analytical levels required to measure mercury in liquid hydrocarbons.  However, getting representative samples and the finding the correct degree of sample preparation provide numerous challenges to the analytical chemist.

Determining the fate of the mercury in any process is very difficult and on numerous occasions it has been shown that a true mass balance has not been achieved.  Many plant shut-downs have occurred worldwide as a direct result of under-estimations of the levels of mercury, usually due to the form of mercury occurring being different from that being analysed for.

The authors have had considerable experience in the measurement and speciation of mercury and will present some of the strategies developed which correctly identify the form of mercury and also provide estimates which correlate well with experience.

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PP022 - Online Determination of Mercury in Liquid Hydrocarbons using Atomic Fluorescence Spectrometry

Authors: Dr Warren T Corns, Dr Peter B Stockwell and Dr Matthew A Dexter (PSA)

Since 2001, the authors have installed a considerable number of online mercury measurement systems for the Natural Gas Industry.  The entire system, from sampling via a series of proven speed loop systems, through to the selection and measurement using the Sir Galahad Atomic Fluorescence Spectrometer have been developed and installed to provide continuous measurement of the levels of mercury on oil platforms and on processing sites.  These systems have been proven to operate reliably and to provide consistent, accurate data on the levels of mercury present. A simple analyzer system, able to provide measurements both before and after mercury removal systems despite there being a 500 fold differential in the levels in each of the streams has been developed.

Experience with these systems and of the latest development where the similar technology has been applied to a liquid hydrocarbon sample stream.  The liquid hydrocarbon is first vaporized to provide a gaseous input to the speed loop and stream selection system.  The speed loop provides a sample representative of the current level in the stream.  All of the components in this assembly have been selected so that they cause no loss or carryover of Mercury.  A calibration accessory developed by the authors enables the user to check that mercury is neither removed nor added to the stream through the sample lines and the speed loop.  This procedure allows the user to have confidence in the performance of the instrument and it the date provided.

Data is provided at regular intervals to update the control room of progress and developments in the process streams.  The instrumentation is installed close to the process stream and as such needs to meet critical demands.  The instrument is installed in an explosion –proof cabinet and is certified to the current ATEX specification.

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PP021 - Test Experience with a Dry-Based Mercury Continuous Emissions Monitor

Authors: Dr Peter B Stockwell, Dr Warren T Corns, Dr Derek Bryce and Dr Matthew A Dexter (PSA)

Over the past 10 years the authors have been working in the field of mercury monitoring for the coal fired utilities sector. Atomic fluorescence spectrometry has provided the performance required to tailor specific sampling technique to measure the levels of mercury (both oxidised and elemental) reliably and continuously.  Wet impinger based technology originally used was able to provide data that correlated well with the industry accepted standards, the Ontario Hydro Method (OHM).  However data was provided within minutes rather than in weeks from the OHM method.  Alternative dry based methodology has been developed and tested on a number of differing sites and found to provide similar data to the original wet based technology.

Systems have been tested over significant periods and the dry based measurements have been both consistent and reliable.  The catalytic converters integrated in the Mercury CEM described have been used effectively over the period without replacement.  As the legislation becomes formalised, the mercury CEM technology will be able to provide the necessary information for process control and allow trading should this be implemented.

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PP020 - Mercury Speciation in Solid Samples by Thermal Decomposition Atomic Fluorescence Spectrometry

Authors: Dr Warren T Corns, Dr Peter B Stockwell and Dr Matthew A Dexter (PSA)

Conventionally, determination of inorganic mercury speciation involves extensive sample preparation such as selective extractions and acid digestions.  An alternative method of speciating mercury in solid samples based on thermal decomposition with atomic fluorescence spectroscopy (TD-AFS) is presented here.

The TD-AFS apparatus consists of a two-stage tubular oven or Thermogram coupled to a Millennium Merlin AFS detector.  Small masses of sample are placed in a sample boat in the first part of the oven which is ranged between 0 and 600ºC.  As the oven temperature is increased the sample gradually undergoes thermal decomposition, the different mercury salts evolving at characteristic temperatures according to their volatility.  A stream of inert gas continuously flows over the sample carrying the evolved gases through the second part of the oven which is maintained at 800ºC to break down the evolved mercury compounds to elemental mercury.  The sample then passes through a Permapure Dryer and into the AFS detector.  Peristaltic pumps and a custom gas-liquid separator on the Millennium Merlin can be used to perform additional online sample pre-treatment if required.

Results for typical Pulverized Fuel Ash (PFA) and barite samples will be presented and calibration techniques discussed.

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PP019 - Atomic Fluorescence Spectrometry - A Sensitive and Cost Effective Solution for Speciation Studies on Arsenic, Selenium and Antimony

Authors: Dr Warren T Corns, Dr Peter B Stockwell and Dr Matthew A Dexter (PSA)

Atomic Fluorescence Spectrometry has long been available as a sensitive and linear technique for many elements.  When coupled to vapour generation, matrix and spectral interferences are overcome. The analytical advantages and superior performance make AFS an ideal detection system for speciation studies.

The authors have worked with many international groups to develop and optimise methodologies and instrumentation to provide cost effective solutions to speciation.  The paper will describe an automated system based on ion chromatography hydride generation AFS for the speciation arsenic, selenium and antimony. Procedures for the online digestion and the conversion of species to the optimal hydride generation valence state will be described.  These will illustrate the capability of the AFS approach. In addition comparison performance data to other techniques such as ICP-MS will be presented.

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Pittcon 2005

PP016 - Developing Standard Methods of Analysis for Arsenic, Selenium and Antimony

Author: Dr Peter B Stockwell (PSA)

As the regulation requirements for the levels of arsenic, selenium and antimony are reduced there becomes an urgent requirement for standard methods of analysis that is suitable for a global market.  As part of its opening commitment to the improvement in the environment P S Analytical has devoted time to working with clients in the European market and globally to develop standard methods of analysis that are suitable for use worldwide and which are fit for purpose of that make use of both Atomic Absorption Spectrometry and Atomic Fluorescence Spectrometry.

A template for these standards is fast established for the determination of antimony by AAS and AFS.  Following consultation further standard methods for Arsenic and Selenium have been established.  Currently these standards are being circulated as a Committee Draft, having been discussed and appraised by the technical working group.  The methods will need to be validated once completed.

An interlaboratory trial will be coordinated so that these standard methods can be validated.  When resources are so stretched to measure environmental pollutants it seems eminently sensible that standards developed within CEN and ISO should be available to EPA and the USA client base.  Further development of these standards towards methods for speciating these elements will also be described.

Peter B Stockwell is the convenor of working group 52 of ISO TC147-SC2.

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PP015 - Speciation of Arsenic in Cornish Soils

Authors: Dr Derek Bryce and Dr Warren T Corns (PSA)

Cornwall (UK) has suffered extensive arsenic pollution due to the historic mining and processing of mineral ores. Current standard practise for contaminated land risk assessment is possibly unviable in Cornwall with very large numbers of sites classified as “contaminated”. Methods of measuring the speciation and mobility of arsenic, rather than just total soil concentration, are essential for effective and rapid risk assessments of arsenic contamination.

A heavily contaminated agricultural site in Cornwall where total soil arsenic values range between 399 and 4264 ppm, was subject to detailed characterisation. Soil pore water was sampled using lysimeters and speciated by High Performance Liquid Chromatography – Hydride Generation – Atomic Fluorescence Spectroscopy (HPLC-HG-AFS). Results show generally low levels of arsenic (0 – 86 ppb) in November 2003, with a variable distribution between arsenate and arsenite. Soil samples removed from the lysimeter sampling points were subjected to a novel method of microwave extraction in orthophosphoric acid. This has been shown to preserve in-situ speciation of arsenic following extraction from solid phases. Analysis of this extract by HPLC-HG-AFS shows arsenic in solid phases to consist predominantly of arsenate. The data suggest that arsenic is relatively immobile under the prevailing environmental conditions.

Solid phase extraction data supports earlier work showing arsenic to be immobilised in diagenetic iron oxides. Variation in the species distribution within the soluble fraction is probably due to soil heterogeneity, with clay lenses and organic material creating potentially reducing microsites in an otherwise aerobic soil. This suggests that a large fraction of the arsenic appears to be immobile. Data from such methods could provide a better baseline for meaningful risk assessment.

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PP014 - The use of Atomic Fluorescence Spectrometry for Mercury Determination in Petrochemical Industry

Authors: Dr Derek Bryce, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Accurate measurements of mercury in petrochemical feedstocks and resulting products is critical for refining operations since the presence of mercury even at low concentrations can have a detrimental effect on numerous refining operations. These include the poisoning of expensive hydrogenation catalysts, corrosion of aluminium alloys of steam cracker cold boxes and reducing product quality.  There are also environmental aspects that have to be considered, since the combustion of hydrocarbons may contribute to the atmospheric emissions of mercury to the atmosphere. Removal of mercury from petrochemicals is extremely challenging and the optimisation of such processes cannot be achieved without knowledge of the mercury species present in the sample and how they might be transformed during refining operations.

This paper will describe how atomic fluorescence spectrometry (AFS) can be applied to the measurement of mercury in petrochemical samples. On and offline measurement of mercury in natural gas was achieved using dual amalgamation – AFS. Data will be presented showing the effectiveness of mercury removal beds. Naphtha and gasoline samples were analysed using a novel volatilisation technique coupled to amalgamation at elevated temperature. This approach allowed part per trillion detection limits without the need for sample preparation. Mercury fractionation in crude oil and condensates was established using various selective extractions with subsequent measurement by cold vapour - AFS. Organic and elemental mercury was determined using a specially designed capillary GC-AFS after direct injection of filtered samples. Experiences from working in the field and typical data from refineries around the world will be presented.

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PP013 - Mercury Speciation in Flue Gas by Catalytic Converters

Authors: Dr Matthew A Dexter, Dr Warren T Corns and Dr Peter B Stockwell (PSA)

Gas-phase mercury in power plant stack gas emissions is present as elemental mercury (Hg0) and oxidised mercury (Hg2+, principally HgCl2).  Current legislative developments are increasing demand for a robust, low maintenance mercury continuous emission monitor (CEM).  Existing wet chemical methods for speciating mercury in flue gas and preconditioning the sample for analysis involve the use of large quantities of reagents, producing similar volumes of liquid waste, and require considerable operator skill and attention.

The flue gas matrix presents particular challenges.  Firstly, representative sampling from the stack, including separation from the reactive flyash without this affecting the mercury speciation or level in the flue gas is necessary.  Secondly, the composition of the flue gas contains significant levels of a range of acid gases (e.g. sulfur dioxide, nitrogen oxides, hydrogen chloride), which can interfere with the determination of mercury.

A dry based mercury speciation module will be described and preliminary results shown.  Mercury is measured in two streams, total gas-phase mercury (HgT) and Hg0, thus speciation by difference can be achieved.  A high temperature catalytic process is used to convert Hg2+ to Hg0 for measurement in the HgT stream and a Hg2+ adsorbent is used to remove Hg2+ from the Hg0 stream.  A peltier cooler is used to remove water from the matrix, prior to determination of mercury in the two sample streams by amalgamation atomic fluorescence spectroscopy (AFS).

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PP012 - Mercury Measurements - Overcoming Contamination and Interferences to Enable the Correct Measurements for Valued Judgements using EPA 1631

Authors: Dr Peter B Stockwell, Dr Warren T Corns and Dr Derek Bryce (PSA)

Interest and concern over the levels of mercury in its various forms in the environment has been well documented over the last 50 years.  Organomercury compounds in particular have received widespread attention, highlighted by the Minamata Bay disaster which sparked off concern over mercury in aqueous eco systems.  Mercury levels in water, soil, petrochemicals and coal fired stack emissions have been regulated for many years.  Permitted levels of mercury are being lowered by regulatory bodies, placing significant demands on the various standard methods of analysis approved both in the USA (EPS methods 1631, 245.1, 245.7 and SW-846 747770-74-71) and the CEN 13506 (soon to be integrated into the ISO regime).  The criterion for fresh water systems is currently set at 12 nanograms/litre (ng/l) and for saltwater the level is 25ng/l [1].  While there are several instruments on the market which can readily measure such levels, there are still major issues to be addressed in order to obtain accurate measurements.  Sampling, storage, pre-treatment, contamination and interferences are all potential sources of error which should be carefully considered before and during analysis using the EPA 1631 approach.

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Pittcon 2004

PP006 - Determination of Antimony in Plant and Geochemical Samples by Hydride Generation Atomic Fluorescence Spectrometry

Authors: Dr Warren T Corns, Dr Peter B Stockwell and Dr Bin Chen (PSA), Michael Krachler and William Shotyk (Institute of Environmental Geochemistry, University of Heidelberg)

A robust and sensitive analytical procedure for the determination of Antimony in plant and geochemical samples using hydride generation-atomic fluorescence spectrometry (HG-AFS) will be described.

The analytical procedure was evaluated by analysing five certified plant reference materials and two in-house peat reference materials.  The dried samples were digested with nitric acid, hydrogen peroxide and tetrafluoroboric acid (HBF4) in a closed-pressurized digestion in a microwave oven.

A solution detection limit of 8 ng l-1 was obtained which corresponds to a method detection limit of 2 ng g-1 in solid peat.  The accuracy and precision (< 3%) of the procedure was evaluated by the determination of Sb in these reference materials.

The results obtained using HG-AFS show that the procedure is more sensitive than other available techniques and also more economic offering a realistic approach to the measurement of antimony in these difficult matrices.

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PP005 - Development and Evaluation of an Inertial Probe for Mercury Speciation in Flue Gas with High Fly Ash Content

Authors: Dr Warren T Corns, Dr Peter B Stockwell (PSA), Tom Baldwin and John Ward (Baldwin Environmental Inc)

Accurate measurement of mercury speciation in flue gas from coal fired power station and waste incinerators is necessary to understand the fate and transportation of mercury in the atmosphere and to evaluate the effectiveness of mercury control technology. One of the most promising Hg removal technologies currently being investigated is activated carbon injection. Alternatively, burner conditions can be optimized to produce un-burnt carbon to maximize mercury capture. Sampling under these conditions is problematic because the gas contains appreciable quantities a fly ash and carbon. Conventional methods of filtering the sample are prone to difficulties because of high ash build up, mercury transformation and capturing of mercury on the filter. To overcome these issues an inertial probe was developed. This works on the principle of delivering a high flow of flue gas down a sintered metal porous filter tube using an eductor. A housing around the filter element creates a minimum volume annular plenum for sample collection. Particulates entrained in the high axial gas flow are prevented from depositing on or penetrating into the porous filter wall by the ballistic effect of particle inertia.

Data will be presented for Hg speciation at sampling locations with high fly ash content.

The inertial probe was evaluated using a dynamic spiking apparatus that generates known concentrations of Hg. The benefits of using an inertial probe arrangement for this application will be described in detail.

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PP004 - Development and Applications of an Online Calibration System for Mercury Analysers

Authors: Dr Warren T Corns and Dr Peter B Stockwell (PSA)

With an increasing need to measure mercury in gaseous phase samples using online Hg analysers an automated calibration system was developed. Traditionally permeation tube devices have been used for this purpose however these suffer from poor accuracy, limited concentration range and long stabilization times. This is particularly noticeable during the aging of the permeation tube or when working a low concentrations.  To overcome these issues a simple yet effective device was developed based on the dilution of a Hg saturated vapour at known temperature. The system uses two NIST certified mass flow controllers to deliver accurate flow rates. A low rate of gas between 1-20 ml/min was passed over a Hg reservoir located in a temperature calibrated oven. This gas becomes saturated with Hg vapour. A dilution gas supplied by the second mass flow controller then dilutes the saturated gas into the concentration range of interest. By varying temperature and flowrate the device offers a wide range of concentrations in the ng/m3 and ug/m3 regions. The accuracy was evaluated using a NIST traceable vapour injection technique used in conjunction with amalgamation – AFS.  In addition to this the concentration was established using traditional impinger based methods such as EPA 101A. The relative accuracy was found to be less than 5% of the theoretical value based on the saturated vapour calculations.

The response time to reach steady state conditions was found to be less than 5 minutes.

Applications will be described where the calibration system has been used for mercury measurements in air, natural gas and flue gas from coal fired power stations will be presented.

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PP003 - Comparative Benefits of Liquid and Gas Chromatography for Mercury Speciation in Environmental Samples

Authors: Dr Peter B Stockwell, Dr Derek Bryce and Dr Warren T Corns (PSA)

Atomic Fluorescence Spectrometry offers excellent analytical performance in the determination of Mercury with sensitivity, linearity, accuracy and precision that are superior to other frequently used techniques. Furthermore, atomic fluorescence detectors are compact, inexpensive and can be readily coupled to separation techniques such as HPLC, Ion Chromatography and GC in order to carry out the speciation of Mercury.

Experiences with these coupled techniques will be outlined showing the performance of each and identifying the relative advantages for real world samples. Procedures from sampling through extraction, pretreatment and measurement will be discussed.

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PP002 - Instrumental Optimisation of Method 1631 for the Determination of Ultra Trace Levels of Mercury in Water

Authors: Dr Derek Bryce and Dr Peter B Stockwell (PSA)

In both USA and Europe the requirements for the measurement of mercury in water samples have been modified to provide lower limits of detection. Cold Vapour Atomic Fluorescence coupled to a preconcentration step has been outlined in EPA 1631. This two stage process requires considerable attention to detail in all aspects of the process from sampling through to measurement. Experience operating system in laboratories worldwide will be described.

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PP001 - Mercury Speciation in Crude Oil using Cold Vapour Atomic Fluorescence Spectrometry

Authors: Dr Warren T Corns, Luther Rahman and Dr Peter B Stockwell (PSA)

Crude oil is a primary feedstock for a variety of industrial processes. Understanding the mercury speciation in crude oil is critical for refining operations since the presence of mercury even at low concentrations can have a detrimental effect on numerous refining operations. Removal of mercury from crude oil and other petrochemical products is extremely challenging and the optimization of such processes cannot be achieved without knowledge of the mercury species present in the sample and how they might be transformed on the refinery.

This paper we will describe various methodologies for extracting mercury species in crude oil. Cold vapour atomic fluorescence spectrometry was used as the measurement technique. Particulate mercury was established by filtering through a 0.45 micron filter and digesting/extracting the filter medium. In the particulate mercury fraction we were able to distinguish between mercury sulphide and insoluble mercury. This was done using high temperature extractions with aqua regia and dilute nitric acid respectively. In the latter case mercury sulphide was not digested and therefore the mercury sulphide content was obtained by difference. For total dissolved mercury two extractions were investigated. Aqua regia extraction was found to give higher recoveries than heated bromination. Ionic mercury was extracted using a saturated solution of potassium chloride. Organomercury and elemental Hg was determined using a specially designed capillary GC- atomic fluorescence spectrometer after a direct injection of the filtered samples. Results will be presented for a wide range of crude oil from different geographical locations.

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