Mercury speciation by coupling cold vapour atomic absorption spectrometry with flow injection on-line preconcentration and liquid chromatographic separation |
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Authors: | Xuefeng Yin Wolfgang Frech Erwin Hoffmann C. Lüdke Jochen Skole |
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Affiliation: | Department of Chemistry, Zhejiang University, 310027 Hangzhou, China, CN Department of Analytical Chemistry, Ume? University, S-90187 Ume?, Sweden, SE Institut für Spektrochemie und angewandte Spektroskopie, Institutsteil Berlin, Laboratorium für spektroskopische Methoden der Umweltanalytik, Geb. 11.1, Rudower Chaussee 5, D-12489 Berlin, Germany, DE
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Abstract: | A fully automated system for the direct determination of methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg), and inorganic mercury (Hg(II)) at the ng/L level is described. It is based on solid phase extraction preconcentration incorporated in a flow injection (FI) system, high performance liquid chromatography (HPLC) separation, reduction combined with thermolysis and determination by cold vapour atomic absorption spectrometry (CVAAS). For preconcentration a microcolumn of bonded silica with octadecyl functional groups (C18 reversed phase material) was used as a sorbent for the mercury complexes formed on-line with ammonium pyrrolidine dithiocarbamate. Retained mercury species are eluted with a methanol-acetonitrile-water mixture and subjected to separation on an octadecylsilane (ODS) column before determination by CVAAS. The sensitivity of organo-mercury determination could be improved by using NaBH4 as a reductant combined with a thermolysis step. In order to perform on-line measurements the preconcentration microcolumn was mounted in a pressure-tight casing. Limits of detection for MeHg, EtHg, PhHg and Hg(II) employing a sample volume of 58.5 mL were 9, 6, 10 and 5 ng/L, respectively. The relative standard deviation (RSD) calculated from 9 repeated measurements was found to be 3.6%, 5.5%, 10.4% and 7.6% for MeHg, EtHg, PhHg and Hg(II), respectively. Finally, the application of this method for speciation of mercury in fish and human urine is described. |
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