Platform in furnace Zeeman-effect atomic absorption spectrometric determination of arsenic in beer by atomization of slurries of sample ash

Abstract

A precise and accurate procedure is proposed for the determination of As in beer samples at the ng g^–1 level by electrothermal atomic absorption spectrometry. The sensitivity of this technique is enhanced by a factor of 2.5 by introducing a preconcentration step, consisting of preliminary dry ashing of the samples and direct injection into the L'vov platform of a slurry of the ashes. The high background caused by the beer sample matrix is compensated for by the use of Zeeman correction. The arsenic is atomized under stabilized temperature platform furnace conditions with the addition of a nickel–ascorbic acid chemical modifier. The effect that each of these compounds has on the determination of As was studied, both separately and in combination. The methodology developed has a characteristic mass of 35 pg, which corresponds to a concentration of 0.7 ng of As per g of beer, a recovery of 102 ± 2% and a relative standard deviation of 4.5% for six independent analyses of a sample containing 8.5 ng g^–1 of As. The accuracy of the method was confirmed by the analysis of a certified reference material sample. The proposed procedure was used to analyse real samples of beer and the results are comparable to those found by hydride generation atomic absorption spectrometry.