On-line dynamic two-dimensional admicelles solvent extraction coupled to electrothermal atomic absorption spectrometry for determination of chromium(VI) in drinking water

An on-line dynamic two-dimensional admicelles solvent extraction system was coupled to electrothermal atomic absorption spectrometry (ETAAS) for determination of Cr(VI) in drinking water. As a two-dimensional solvent, admicelles were on-line-prepared by passing cetyltrimethylammonium bromide (CTAB) through a microcolumn packed with silica gel. The analyte Cr(VI) was on-line-complexed with pyrrolidine dithiocarbamate (PDC), and the resulting Cr(VI)-PDC was effectively adsolubilized in the admicelles of the microcolumn, and then quantitatively eluted with 30 μl of acetonitrile for ETAAS determination. All the procedures including the formation and decomposition of admicelles and ETAAS determination were performed on-line, ensuring automatic determination of Cr(VI) in drinking water with a high precision. With a consumption of 2.1 ml sample solution, a detection limit (3σ) of 3.0 ng l−1, and an enhancement factor of 32 were obtained at a sample throughput of 31 samples h−1. The precision (R.S.D.) for 11 replicate measurements of 50 ng l−1 Cr(VI) was 2.5%. The developed methodology was demonstrated to be reliable and sensitive for automatic determination of ultratrace Cr(VI) in bottled drinking water samples.