Selective determination of inorganic mercury and methylmercury in tissues by continuous flow and cold vapor atomic absorption spectrometry.

A method has been developed for the determination of inorganic (InHg) and methylmercury (MeHg) in solubilized tissues with continuous-flow (flow injection) cold vapor atomic absorption spectrometry. Kidney, liver, and brain tissues were spiked with MeHg and InHg and solubilized at an elevated temperature in a solution containing 90 g/L NaOH, 2 g/L L-cysteine, and 4 g/L NaCl. Total mercury determination was achieved by continuous-flow cold vapor atomic absorption spectrometry using an inlet system containing a flow through photo-oxidation reactor and sodium borohydride as the mercury reductant. InHg was selectively determined in the presence of MeHg with this method when using stannous chloride as the reductant. MeHg concentrations were computed as the difference between the values obtained from the two analyses. Recoveries for spiked tissues were above 95% for InHg and MeHg. Quantitation limits for InHg and total mercury in tissues were 0.4 and 0.6 microgram/g, respectively. MeHg chloride levels from kidney tissues of exposed rats were evaluated using the present method in comparison with another method in which MeHg was measured using solvent extraction and capillary gas chromatography with electron capture detection.