Ion chromatographic separation and on-line cold vapour atomic absorption spectrometric determination of methylmercury, ethylmercury and inorganic mercury

The ion chromatographic separation of methylmercury, ethylmercury and inorganic mercury as cysteine complexes was investigated. The chromatographic apparatus was interfaced with cold vapour atomic absorption spectrometry for detection using an on-line continuous flow cell coupled with a reduction system (sodium tetrahydroborate). The influence of the composition of the eluent (pH, ionic strength, cysteine concentration) and stripping gas flow-rate was investigated. The method was optimized by coupling an on-line preconcentration step. The detection limits, evaluated on 100.0-ml samples, were 2, 10 and 4 ng for Hg, CH₃Hg and C₂H₅Hg, respectively. The method was applied to synthetic mixtures and natural samples (tap water) and furnished satisfactory results.