Determination of inorganic and organic anionic arsenic species in water byion chromatography coupled to hydride generation-inductively coupled plasma atomic emission spectrometry

The development of an analytical methodology for the specific determination of arsenite, arsenate and the organic species monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), is described. The method is based on an io n chromatographic separation, coupled on-line to post-column generation of the gaseous hydrides by reaction with sodium tetrahydroborate in acidic med ium. Detection and measurement were performed by inductively coupled plasma spectrometry operated in the atomic emission mode. Arsenic emission was mo nitored at 193.7 nm. Different types and sizes of anion-exchange columns, s ilica and polymeric, were tested using EDTA as eluent. Composition, acidity and flow-rate of the mobile phase were optimized in order to obtain the re quired resolution. Complete elution and resolution of the four species was achieved in about 6 min. Linear calibration curves were obtained in the 0.0 5-2 mu g ml(-1) range for As(III), As(V) and MMA, and between 0.1 and 2.0 m u g ml(-1) for DMA. The absolute limits of detection for 200-mu l sample in jections were in the ng range, with DMA the compound measured with less sen sitivity. Results of the analyses of natural samples, such as river and gro und waters spiked with the studied species, suggested that analyte recoveri es might be dependent on the sample composition. (C) 2000 Elsevier Science B.V. All rights reserved.