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

Hydride generation (HG) is a sample introduction technique that provides en hanced sensitivity for metalloids and allows chemical speciation between se lected arsenic (As) and selenium (Se) anion species. The present studies ha ve demonstrated high sensitivity for As, Se, and antimony (Sb) using contin uous flow HG-laser induced fluorescence (LIF) and HG-laser enhanced ionizat ion (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. Measu rements 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 o btained using the flame HG-LIF approaches. Selective determinations of Se(I V) and Se(VI) have been carried out using an on-line pre-reduction procedur e, 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 degreesC. 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 demonst rate that the HG approaches are selective and provide quantitative recoveri es of the individual Se and As species at sub-ppb levels.