Speciation analysis of mercury in sediments, zoobenthos and river water samples by high-performance liquid chromatography hyphenated to atomic fluorescence spectrometry following preconcentration by solid phase extraction.

A high-pressure microwave digestion was applied for microwave-assisted extraction (MAE) of mercury species from sediments and zoobenthos samples. A mixture containing 3molL(-1) HCl, 50% aqueous methanol and 0.2molL(-1) citric acid (for masking co-extracted Fe(3+)) was selected as the most suitable extraction agent. The efficiency of proposed extraction method was better than 95% with R.S.D. below 6%. A preconcentration method utilizing a "homemade" C18 solid phase extraction (SPE) microcolumns was developed to enhance sensitivity of the mercury species determination using on-column complex formation of mercury-2-mercaptophenol complexes. Methanol was chosen for counter-current elution of the retained mercury complexes achieving a preconcentration factor as much as 1000. The preconcentration method was applied for the speciation analysis of mercury in river water samples. The high-performance liquid chromatography-cold vapour atomic fluorescence spectrometric (HPLC/CV-AFS) method was used for the speciation analysis of mercury. The complete separation of four mercury species was achieved by an isocratic elution of aqueous methanol (65%/35%) on a Zorbax SB-C18 column (4.6mmx150mm, 5microm) using the same complexation reagent (2-mercaptophenol). The limits of detection were 4.3microg L(-1) for methylmercury (MeHg(+)), 1.4microg L(-1) for ethylmercury (EtHg(+)), 0.8microg L(-1) for inorganic mercury (Hg(2+)), 0.8microg L(-1) for phenylmercury (PhHg(+)).