Biennial National Atomic Spectroscopy Symposium (BNASS)

Biennial National Atomic Spectroscopy Symposium (BNASS) 2016

PP094 - Speciation of Mercury by HPLC-CV-AFS based on a new and simple extraction method

Authors: Christoph-Cornelius Brombach, Dr Warren T Corns & Matthew A Dexter

Mercury is among the most toxic elements and the toxicity, bioavailability, and transportation way depends on the mercury species. Methylmercury is a neurotoxin which biomagnifies throughout the aquatic food chain. In humans, MeHg is almost completely absorbed in the gastrointestinal tract.  It is transported through the blood into the brain where it can cause severe damage to the central nervous system. Therefore, speciation of mercury is a crucial tool to assess the contamination of our food and environment.

This poster presents a quick and easy extraction method for mercury species in hair and fish samples using ammonium pyrrolidinedithiocarbamate in 80 % (v/v) methanol. The extraction medium is also used as the mobile phase for HPLC-CV-AFS, so the extract only requires filtering before injection. The recoveries for hair reference material IAEA-086 were 95.2±0.5 % and for fish reference material DOLT-4 96.9±1.1 % with this method. This new method is a simpler than most extraction methods for HPLC and CV-AFS is a sensitive, robust and cost-effective detection.

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

Authors: Dr Bin Chen, Dr Matthew A Dexter & Dr Warren T Corns

The US EPA has proposed new Effluent Guideline Limits (40 CFR, part 423) in an attempt to reduce the amount of toxic metals and other pollutants discharged to surface water from coal-fired utilities.  The previous regulations did not consider the additional burden of water discharge pollutants from air pollution control systems such as flue gas desulfurisation (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). 

The new regulations will impose new and additional requirements for wastewater associated with many wastewater streams from coal-fired utilities, including FGD wastewater.  The best available technology (BAT) that is economically achievable is mandated to reduce pollutant discharges.  This is particularly important for dissolved forms of As, Se and Hg as they are not removed by surface impoundments.  Waste streams cannot be comingled or diluted to meet discharge limits without first establishing pollutant levels.  Online monitoring of pollutant levels is desirable to confirm the efficiency of the wastewater treatment process and for compliance monitoring.

Analysis of FGD wastewater is a challenging application due to the high levels of dissolved solids, chloride content, potential for sample matrix interference and the low permitted discharge concentrations.

This poster presents online approaches for the determination of mercury, arsenic and selenium in FGD wastewater using atomic fluorescence spectrometry (AFS).  Online sampling and measurement equipment is described and compared with data for laboratory measurements.


Biennial National Atomic Spectroscopy Symposium (BNASS) 2014

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

Authors: Dr Matthew A Dexter, Dr Warren T Corns & 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 the species present and, in some cases, the sample matrix.  Elemental mercury calibration is widely available.  In some applications, such as ambient air and coal-fired utility stack monitoring, oxidised sources of mercury are also needed.

Calibration of mercury analysers used for the automated monitoring of ambient air is frequently in the 0.1-10 ng mass range, potentially orders of magnitude above the masses collected during air monitoring.  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.  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’ results can affect the average emission levels as much as poorly monitored mg/m3 spikes.)

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 a 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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PP078 - Selenium Speciation in Ruminant Livestock Feed using Liquid Chromatography Hydride Generation Atomic Fluorescence Spectrometry (HPLC-HG-AFS)

Authors: Michael R. F. Lee (Bristol Uni and North Wyke - Rothamsted Research), Hannah R. Flemming (North Wyke - Rothamsted Research) and Dr Bin Chen and Dr Warren T Corns (PSA)

An inadequate supply of Se to livestock can lead to increased health and welfare problems. In dairy cows for example, Se deficiency 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. Accepting that the cause for these conditions is often difficult to identify, mineral deficiency is recognised as being significantly responsible and this is a key reason why there is increased culling on dairy farms which result in high economic and environmental costs. In addition to effects on adult ruminants, there are numerous consequences for Se deficiencies in newly born calves and lambs with conditions such as ill-thrift, brought about by reduced eagerness to suckle milk and white muscle disease, which causes general stiffness and in extreme cases the inability to stand and ultimately death. It is therefore common place to supplement for these deficiencies. Currently ‘on-farm’ mineral supplementation is either by the incorporation of minerals into complete rations or by the provision of mineral blocks (licks) accessible to livestock at all times. Although supplementation with inorganic minerals such as sodium selenite should overcome these problems, it is known that ruminants are less able to absorb inorganic Se to an even greater extent than monogastrins with <50% absorbed. In addition, the inorganic form of Se is less readily converted into milk Se than its organic counterpart, giving rise to additional inadequacies in the supply of Se to calves and lambs and also for humans consuming dairy and meat products. 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 (selenite, selenate, selenocysteine, selenocystine and selenomethionine) have been investigated in this study. The extraction procedure from livestock feed samples and the separation of the five selenium species on an anion exchange column is investigated and optimised in this presentation. HG-AFS technical is used for the detection of selenium signals with detection limits between 0.13 and 0.43 ng (3s).

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ORAL - Mercury Mass Balance Studies on an Ethylene Plant using AFS

The following oral presentation is currently under review and will be put online as soon as possible. Please check again soon.

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Biennial National Atomic Spectroscopy Symposium (BNASS) 2008

PP038 - Sampling - Still the Achilles Heel for Accurate Mercury Measurements in Petrochemical Samples

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

As we increase our knowledge of measurement techniques in analytical science, little, if any, effort is being made on the Achilles Heel of analysis – the provision of a truly representative sample.  Mercury is of considerable interest in the Petrochemical industry as it causes many failures of processing plants.  Atomic fluorescence measurements, combined with well designed sampling strategies provide the Petrochemical industry with three mechanisms to (a) determine the levels of mercury present in the samples (b) the precise distribution of the mercury species and (c) the mechanisms to remove the mercury species and render the sample suitable for continuing use in the industry.

Atomic fluorescence spectrometry provides a viable measurement tool which coupled to tailored sampling systems for both online and offline applications serve the industry well.  Experiences operating several systems which range from natural gas to liquefied natural gas condensates will be described.  Many of these systems have been operating continuously since 1996.

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Biennial National Atomic Spectroscopy Symposium (BNASS) 2004

PP011 - Mercury Fractionation in Crude Oil and Natural Gas Condensates using Cold Vapour Atomic Fluorescence Spectrometry

Authors: Dr Warren T Corns, L 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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PP010 - Interference Studies for the Determination of Mercury and the Hydride Forming Elements using Vapour Generation Atomic Fluorescence Spectrometry

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

Vapour generation atomic fluorescence spectrometry offers many advantages in the determination of mercury, arsenic, antimony, selenium, bismuth and tellurium.  Detection limits are in the low ng l-1 range while linearity extends to μg l-1 levels with good precision.  The technique is also relatively free from interferences, which can be split into 2 classes; chemical and spectral.  Chemical interferences tend to affect the vapour generation process and usually lead to a suppression of the analytical signal, while spectral interferences during the detection step generally cause a false signal enhancement.  Chemical interferences can usually be overcome by selection of an alternative chemistry or by dilution of the sample, an approach made feasible by the inherent sensitivity of atomic fluorescence, while spectral interferences are minimized by the use of vapour generation as a means of sample introduction and the selectivity of the technique.

The presentation will outline interference studies for mercury, arsenic, antimony, selenium, tellurium and bismuth and discuss how alternative chemistries and instrumental design have been used to minimize interferences.  Examples of applications will be shown with results for real samples and certified reference materials for a wide range of matrices.

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