Determination of As, Sb, Se, Sn and Hg in beer and wort by direct hydride generation sample introduction−electrothermal AAS

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Abstract
A method is described for the hydride generation atomic absorption (HG-AAS) determination of As, Sb, Se, Sn and Hg in untreated samples of beer and wort using a batch system and in situ preconcentration of the analytes onto the Pd- (for As, Sb, Se, Sn) or Au-pretreated (for Hg) interior wall surfaces of a graphite furnace. Samples were degassed by filtration and the hydride was generated in the presence of an antifoam agent. Instrument parameters, hydride generation, transportation and trapping were selected. Determination of the total concentration of these elements was obtained after a previous reduction with thiourea. To minimize the amount of moisture from the reaction vessel reaching the graphite tube, an extra gas–liquid separator was installed in line. For 10 mL of sample, detection limits (LOD, 3σblank, peak height) of 28, 21, 10, 50 and 90 ng L−1 were obtained for As, Sb, Se, Sn and Hg, respectively, reflecting overall generation/collection efficiencies of 53, 100, 54, 57 and 66%, respectively. The detection limits were restricted by variations in the blank absorbance. Precision of replicate determination was typically 5% RSD at a concentration 50-fold above the LOD for a 10 mL sample volume. The accuracy of the method was confirmed by comparing the results obtained with those found for beer and wort using microwave-assisted digestion and by analysing five certified reference materials. Data comparable with those obtained by hydride generation after microwave-assisted digestion of samples were found for a series of natural samples, giving evidence of the applicability of the developed methodology to directly determining analytes. Calibration was achieved via the method of standard additions.

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