Direct mercury determination in aqueous slurries of environmental and biological samples by cold vapour generation-electrothermal atomic absorption spectrometry

Direct cold vapour generation from aqueous slurries of environmental (marine sediment, soil, coal) and biological (human hair, seafood) samples have been developed using a batch mode generation system coupled with electrothermal atomic absorption spectroscopy. The effects of several variables affecting the cold vapour generation efficiency from solid particles (hydrochloric acid and sodium tetrahydroborate concentrations, argon flow rate, acid solution volume and mean particle size) have been evaluated using a Plackett-Burman experimental design. In addition, variables affecting cold vapour trapping and atomisation efficiency on Ir-treated graphite tubes (trapping and atomisation temperatures and trapping time) have been also investigated. Atomisation and trapping temperatures, trapping time and hydrochloric acid concentration were the significant variables. The 2(2) + star and 2(3) + star central composite designs have been used to obtain optimum values of the variables selected. The accuracy of methods have been verified by using several certified reference materials (PACS-1, GBW-07410, NIST-1632c, CRM-397 and DORM-2). A characteristic mass of 390pg were achieved. The detection limits of methods were in the range of 40-600ng g(-1). A particle size less than 50 mum is adequate to obtain total cold vapour generation of Hg content in the aqueous slurry particles. (C) 2002 Elsevier Science B.V. All rights reserved.