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-line leaching in the flow injection manifold. Slurries, prepared by mixing the soil (particle size <65 microm) 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 microL) 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 microg/mL As), river sediment CRM 320 (76.7 microg/mL As), and soil GBW 07405 (412 microg/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%.
A flow injection-pervaporation method for the continuous derivatisation and determination by atomic fluorescence spectrometry is proposed for the first time in order to speciate As as As III and As V . The sample at different pHs was injected into a 6 M HCl stream and then mixed with 0.5% or 0.05% m/v NaBH 4 . The reactant mixture was transported to the lower chamber of a pervaporator from which the arsine generated evaporated to the air gap between the liquid and the membrane, diffused through the latter and was swept out of the acceptor chamber by a hydrogen-argon stream into the chemically generated hydrogen diffusion flame. An auxiliary H 2 flow was necessary to support the flame. The linear ranges of the calibration curves for As III and As V were from pg ml 21 to ng ml 21 , with correlation coefficients, r 2 , better than 0.99. For As III , the reproducibility and repeatability, expressed as relative standard deviation, were 3.0% and 1.1%, respectively, and for As V were 3.2% and 1.3%, respectively. The detection and quantification limits were 0.42 ng ml 21 and 0.61 ng ml 21 for As III and AS V , respectively. The method thus developed was applied to 'dirty' aqueous samples with solid particles in suspension, without prior filtration, and provided a sampling frequency of 12 h 21 .
Experimental ApparatusAn Excalibur PSA 10033 non-dispersive atomic fluorescence detector (PS Analytical, Orpington, UK) fitted with a monoelemental boosted discharge hollow cathode lamp (primary current 27.5 mA, boosted current 35.0 mA, Victoria, Australia) for As, as the excitation source, a hydrogen diffusion flame, as the atom cell, and a specific filter to achieve isolation and reduction of flame emission in conjunction with a solar blind
A dynamic system for the continuous removal of ammonia from cigarettes with ultrasound assistance and iterative change of the flow direction of the extractant through the sample cell has been developed. A 0.1-g sample of cigarette was subjected to 7 min of ultrasound-assisted extraction (application and duration of pulse 0.7 s, output amplitude 85% of the converter nominal amplitude), and 1 M NaOH solution was used both as extractant and as carrier in the dynamic system. The ultrasound-assisted extractor was coupled to a pervaporation unit through a flow injection interface in order to develop a fully automated method. In arriving at the pervaporator, the ammonia is transferred from the donor-carrier stream to an acceptor stream, where the classical Berthelot reaction takes place--thus favoring pervaporation. The blue complex formed is spectrophotometrically monitored at 655 nm. The method was applied to the determination of ammonia in a selection of 10 European cigarette brands and Kentucky Reference 2R4F cigarettes.
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