Hydride generation-pervaporation-atomic fluorescence detection prior to speciation analysis of arsenic in dirty samples

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 NaBH4. 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(-1) to ng ml(-1), 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 quanti cation limits were 0.42 ng ml(-1) and 0.61 ng ml(-1) 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-(1).