Flow injection on-line sorption preconcentration coupled with hydride generation atomic fluorescence spectrometry using a polytetrafluoroethylene fiber-packed microcolumn for determination of SeIVin natural water

Polytetrafluoroethylene PTFE fiber was demonstrated as a new sorbent for flow injection on-line sorption preconcentration of trace elements. The on-line PTFE fiber packed microcolumn preconcentration system was coupled with hydride generation atomic fluorescence spectrometry HG-AFS for the determination of ultratrace selenite SeIV in natural water. Selective determination of SeIVin aqueous solution was achieved by on-line formation of SeIV–pyrrolidinedithiocarbamate PDC complex over a wide sample acidity range of 0.01–50 vv HCl, its sorption onto the surface of the PTFE fiber in the microcolumn, elution with 3 mv KBH4in 0.5 mv KOH, hydride generation with 15 vv HCl solution and determination with atomic fluorescence spectrometry. The alkaline KBH4solution was employed not only as an efficient eluent but also as the reductant to produce selenide anion for subsequent hydride generation. With a consumption of 12.4 ml of sample solution, a detection limit 3σ of 4 ng l−1was achieved at a sample throughput of 26 samples h−1. The retention efficiency was 67, being five times that obtained with a PTFE knotted reactor KR. The linear ranges of the diagrams of signal intensity against sample loading flow rate, and sample loading time, were much wider than those achieved with a KR, offering more potential for obtaining high sensitivity by increasing sample loading rates andor sample loading time. The precision for 11 replicate measurements of 0.5 µg l−1SeIVwas 1.5 RSD. The recoveries of SeIVfrom natural water samples varied from 96 to 108. The concentration of SeIVin a certified reference material NASS-5, sea-water determined by the present method with a simple aqueous standard curve calibration was in good agreement with the certified value. The developed method was also successfully applied to the detection of SeIVin local river water, lake water and sea-water samples.