Determination of organomercury compounds in aqueous samples by capillary gas chromatography-atomic fluorescence spectrometry following solid-phase extraction

A new method based on capillary gas chromatography-atomic fluorescence spectrometry (GC/AFS) is described for the determination of methylmercury (MeHg) and ethylmercury (EtHg) in water samples. An improved sample preparation methodology was developed, which involves preconcentration of the alkylmercury species from water samples, drawn with a 12 channel peristaltic pump, onto sulfhydryl cotton fiber (SCF) adsorbent packed in a screening column, elution of MeHg and EtHg with a mixture of acidic potassium bromide and copper sulfate solution, and back-extraction using methylene chloride. Analysis was performed by capillary GC/AFS with a DB-1 column. Some important parameters, including sample pH, presence of anions and cations, concentration of dissolved organic carbon (DOC), eluent type, and eluent volume were evaluated. With AFS as a detector, the capillary gas Chromatographic technique provides high selectivity, high sensitivity, and a straightforward method for organomercury halide analysis. It eliminates possible spectral interferences to the detector from other sample components and from chemicals used in the sample preparation procedure. The detection limit was 0.01 ng l −1 in a 11 water sample for both MeHg and EtHg. The result for organomercury analysis in a number of natural water samples is shown to illustrate the applicability of this method to real environmental samples.