SIMPLE SOLVENT-EXTRACTION TECHNIQUE FOR ELIMINATION OF MATRIX INTERFERENCES IN THE DETERMINATION OF METHYLMERCURY IN ENVIRONMENTAL AND BIOLOGICAL SAMPLES BY ETHYLATION GAS-CHROMATOGRAPHY COLD VAPOR ATOMIC FLUORESCENCE SPECTROMETRY

A solvent extraction technique involving no critical clean-up steps wa s developed for the determination of methylmercury (MeHg) in environme ntal and biological samples by aqueous phase ethylation, room temperat ure precollection, gas chromatographic separation and cold vapor atomi c fluorescence spectrometric detection, Samples were first digested wi th KOH-methanol, then acidified prior to extraction with methylene chl oride. MeHg was back-extracted from the solvent phase into water prior to aqueous phase ethylation. Recoveries close to 100% were obtained w ith RSDs less than 5% for all samples analyzed, making direct standard ization possible. The detection limits were about 0.08 ng g(-1) when a nalyzing 0.1 g of dry sea plant homogenate and 0.02 fig g when analyzi ng 0.5 g of wet sediment samples. Various certified reference material s and intercomparison samples, including sediments, sea plants and tis sues, were analyzed, and the results were in good agreement with the c ertified values. The technique was applied to the determination of MeH g in both sea plants from the Atlantic and the red blood protein of do lphins from the Mediteranean Sea, in sediments from the Mediterranean Sea and Minnesota rivers and in soils from different origins. Concentr ations of MeHg in dolphin red blood protein samples were as high as 30 0 ng g(-1).