EspeQBrasil 2008

PP039 - Speciation of Arsenic and Selenium in Various Samples using HPLC Coupling with Vapour Generation Atomic Fluorescence Spectrometry

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

Petrochemical products are primary feedstock for a variety of industrial processes.  Understanding the mercury speciation in these samples 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 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 carried out 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.  This procedure is also suitable for mercury speciation in other petrochemical products.

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