A comparison of continuous flow hydride generation laser-induced fluorescence and laser-enhanced ionization spectrometry approaches for parts per trillion level measurements of arsenic, selenium and antimony

Abstract

Hydride generation (HG) is a sample introduction technique that provides enhanced sensitivity for metalloids and allows chemical speciation between selected arsenic (As) and selenium (Se) anion species. The present studies have demonstrated high sensitivity for As, Se, and antimony (Sb) using continuous flow HG-laser induced fluorescence (LIF) and HG-laser enhanced ionization (LEI) spectrometric techniques. The limits of detection (LODs) are 200, 90 and 300 fg ml−1 for As, Se and Sb, respectively, using HG-LIF and 50 and 2 pg ml−1 for As and Se, respectively, using HG-LEI approaches. Measurements performed using HG combined with LIF detection in an electrothermal atomizer resulted in LODs of 3 pg ml−1 (6 pg absolute mass) and 20 pg ml−1 (40 pg) for As and Se, respectively. All of the techniques are linear in their responses to at least 10 ng ml−1 for the corresponding elements. Reliable chemical speciation of As(III/V) and Se(IV/VI) species has been obtained using the flame HG-LIF approaches. Selective determinations of Se(IV) and Se(VI) have been carried out using an on-line pre-reduction procedure, where selective HG of Se(IV) is performed in 31% HBr at room temperature, while HG of [Se(IV) + Se(VI)] is performed following pre-reduction in 31% HBr at 100°C. Selective HG of As species is accomplished by control of the solution pH, where selective HG of As(III) is performed at pH 6 and HG of [As(III) + As(V)] is performed at pH 0. The results obtained demonstrate that the HG approaches are selective and provide quantitative recoveries of the individual Se and As species at sub-ppb levels.