Development of a proposed International Standard for determining arsenic in workplace air using hydride generation atomic absorption spectrometry

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Proposed Draft International Standard DIS 11041, described and developed by the International Organisation for Standardisation (ISO), involves sampling air by drawing it though a membrane filter with a paper back-up pad, both of which have been treated with sodium carbonate solution. Particulate arsenic compounds and arsenic(III) oxide vapour are collected, but not arsine. The filter and pad are digested using nitric acid, sulfuric acid and hydrogen peroxide. The resultant solution is boiled down to sulfuric acid fumes and then made up to volume with water. Aliquots of the sample solution are prepared for hydride generation by the addition of hydrochloric acid and potassium iodide. Analysis by both continuous flow and flow injection hydride generation atomic absorption spectrometry (HG-AAS) is described. The method exhibits a recovery of > 95%. It can be adapted to determine nanogram to milligram levels of collected arsenic, making it suitable for testing compliance with the widely differing limit values stipulated in government health legislation of different countries, e.g., 0.1 mg m–3 UK Maximum Exposure Limit (MEL), 0.01 mg m–3 US Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) and 0.002 mg m–3 US National Institute of Occupational Safety and Health (NIOSH) Short Term Limit Value. The International Standard will supplement existing internationally adopted analytical standards, such as NIOSH 7901 which employs electrothermal atomic absorption spectrometry, and NIOSH 7900, which employs HG-AAS but which for safety reasons requires the use of a fume cupboard suitable for handling perchloric acid. It should be useful to a wide range of laboratories, including those with limited AAS facilities. This paper describes the testing protocol used to validate the method and gives results obtained to date, including some obtained by laboratories using the analytical method in an inter-laboratory exercise.