Simultaneous determination of methyl-, ethyl-, phenyl- and inorganic mercury by cold vapour atomic absorption spectrometry with on-line chromatographic separation

A fully automated system for on-line high-performance liquid chromatographic separation, reduction and determination by cold vapour atomic absorption spectrometry (CVAAS) of methyl-, ethyl-, phenyl- and inorganic mercury is described. Reversed-phase chromatography on an ODS column and elution with an acetonitrile-water-ammonium tetramethylenedithiocarbamate buffered mixture was investigated with or without ammonium tetramethylenedithiocarbamate precomplexation. A simple glass flow cell, properly designed as an interface between the chromatographic system and CVAAS, is proposed. The influence of the composition of the eluent, reducing solution and stripping gas flow-rate was investigated and optimized in order to obtain better detection limits. The method, applied to synthetic mixtures and natural samples of tap water furnished satisfactory results. It is shown that, with the on-line preconcentration procedure, sub-ng/ml concentration levels can be determined for all the species considered.