Chemical vapor generation from an ionic liquid using a solid reductant: determination of Hg, As and Sb by atomic fluorescence spectrometry

Abstract

Generation of volatile hydrides and elemental mercury was accomplished in non-aqueous media by using a solid reductant of lithium aluminium tetrahydride (LiAlH₄), stannous chloride dehydrate (SnCl₂) or tetrahydroborate (THB) as a derivation reagent. A room temperature ionic liquid (RTIL) was used as the non-aqueous media for the chemical vapor generation (CVG), and atomic fluorescence spectrometry was used for the elemental determination. The analyte ions were firstly extracted into the RTIL media from the bulk aqueous phase of the analyte/sample solution via a liquid–liquid extraction process and then directly mixed with the solid reductant to generate volatile analyte-containing species, which were then rapidly transported to a commercial atomic fluorescence spectrometer for detection. Hg(II), As(III) and Sb(III) were selected as the model analytes for evaluating this new CVG technique. The three reductants could all reduce Hg(II) to the elemental state, but only THB could generate volatile species of As(III) and Sb(III). Compared to conventional CVG in the aqueous phase, the efficiencies of CVG accomplished with solid reductants were similar or even better, there was less interference from transition and noble metal ions, and much better limits of detection were obtained. The proposed method was successfully used for the determination of ultratrace mercury and arsenic in several certified reference materials, including soil, water and human hair samples.