Multivariate optimization of photochemical vapor generation for direct determination of arsenic in seawater by inductively coupled plasma mass spectrometry

• Direct and accurate determination of ultra-trace level of total As in heavy matrix seawater using PVG ICPMS.
• The impact of the saline matrix on the suppression of analyte signal is efficiently eliminated by use of a mixture of 20% (v/v) formic and 20% acetic acid (v/v) as the photochemical reductants.
• Proposed method provides a 13-fold enhancement in sensitivity and 15-fold improvement in detection limit.

Photochemical vapor generation (PVG) sample introduction coupled to inductively coupled plasma mass spectrometry (ICPMS) is described for the determination of As in seawater. A Plackett–Burman design (PBD) and central composite design (CCD) were employed to evaluate the significance of experimental variables relevant to the optimization of PVG-ICPMS detection. The impact of the saline matrix on the suppression of analyte signal was eliminated by use of a mixture of 20% (v/v) formic and 20% acetic acid (v/v) as the photochemical reductants. Optimized conditions yielded equivalent PVG generation efficiencies for As(III), As(V), monomethylarsonic acids (MMAs) and dimethylarsinic acids (DMAs), permitting direct and rapid determination of total arsenic in seawater without any other sample pre-treatment. Quantitation was accomplished using one point gravimetric standard addition along with a spike of 82Se internal standard to compensate for signal drift and fluctuation during analysis. The resulting method detection limit of 3 pg g−1 (3σ) provided a 15-fold improvement over that obtained using direct solution nebulization, and is comparable to that for conventional chemical hydride generation (HG)-ICPMS. Accuracy was demonstrated by analysis of two Certified Reference Materials (NASS-6 and CASS-5 seawater) with satisfying results characterized by precisions of 3.5% and 3.2% RSD for CASS-5 and NASS-6, respectively.

A sensitive and accurate approach is developed for the direct determination of total As in seawater based on thin-film photochemical vapor generation (PVG) for sample introduction and ICPMS detection using multivariate optimization.Figure optionsDownload as PowerPoint slide