Arsenic speciation with gradient hydride generation interfacing liquid chromatography and atomic absorption spectrometry

Abstract

Arsenic speciation was performed based on liquid chromatographic separation followed by gradient hydride generation (GHG) and quartz atomizer atomic absorption spectrometric detection. The arsenic species, i.e., arsenate (As(V)), arsenite (As(III)), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and trimethylarsine oxide (TMAO), were separated on C30-5 columns, and the concept of gradient hydride generation facilitates high conversion efficiency of the arsenic species into corresponding hydrides. The use of 2% L-cysteine in the GHG process gives rise to further improvements on the hydride generation efficiency of 13% to 32% for the arsenic species. The hydrides were separated in a unique design of gas–liquid separator, which not only ensures a complete separation but minimizes the dispersion of hydrides when delivering into the atomizer, resulting in a maximum of 13-fold improvement on the sensitivity of As(V) compared to previous studies. A separation process was finished within 800 s by injecting 100 µL sample solution, achieving detection limits of 0.9, 1.4, 1.4, 1.6, 1.5 µg/L, respectively, for As(V), As(III), MMA, DMA and TMAO. Precisions of less than 3% and 6% RSD were obtained for the five arsenic species at 100 µg/L and 20 µg/L, respectively. Three arsenic species, i.e., As(V), DMA and TMAO, were identified in Hijiki samples by this procedure.