Slurry sampling-microwave assisted leaching prior to hydride generation-pervaporation-atomic fluorescence detection for the determination of extractable arsenic in soil

A flow injection-pervaporation method, where the sample was introduced as slurry, has been developed for the continuous derivatization and determination of arsenic in soil by hydride generation-atomic fluorescence spectrometry. The removal of arsenic is achieved with the help of a microwave digestor, which facilitates an on-fine leaching in the flow injection manifold. Slurries, prepared by mixing the soil (particle size <65 mum) with 6 mol L-1 HCl, were magnetically stirred for 3 min, and while stirring, the pump aspirated the aliquot and filled the loop (500 muL) of the injection valve. An industrial soil and five types of soil (sandy, clayey, slimy, limy, organic) were selected for the optimization of the leaching and determination steps of arsenic, respectively. The results obtained from three certified reference materials [stream sediment GBW 07311 (188 mug/mL As), river sediment CRM 320 (76.7 mug/mL As), and soil GBW 07405 (412 mug/mL As)] using direct calibration against aqueous standards demonstrate the reliability of the method. The relative standard deviation for within-laboratory reproducibility was 4.5%.