Optimisation of high-performance liquid chromatographic separations with reductive amperometric electrochemical detection: speciation of inorganic and organomercury

Abstract

Reversed-phase charge neutralisation high-performance liquid chromatography with reductive amperometric electrochemical detection was optimised for the simultaneous determination of inorganic and organomercury in aqueous solution under ideal conditions. The optimum electrochemical (electrode reduction potential) and chromatographic (capacity factors, separation factors, flow-rates, modifier concentrations and retention times) conditions were determined for maximum selectivity, sensitivity and resolution in conjunction with minimum analysis times. The determinations were performed under isocratic conditions with acetonitrile and methanol as the organic modifiers, buffered at pH 5.5. Acetonitrile, the stronger eluent, had a dramatic effect on the retention time of the aromatic organomercury species. Separation of the analytes was performed on octadecylsilane columns (250 × 4 mm i.d.) with organic modifier ratios ranging from 10 to 70%m/m. The gold amalgamated mercury electrode under the optimum conditions had a useful working range from –0.3 to –1.0 V vs. an Ag-AgCl reference electrode.