Direct determination of silver in geological reference samples after aqua regia leach by graphite furnace atomic absorption spectrometry with matrix modification

Summary Silver was determined in 20 different geological samples by electrothermal AAS with and without (NH₄)₂HPO₄ matrix modifier after aqua regia leach. The results were compared with those obtained after total dissolution of samples.The ashing temperature can be 300 °C higher and the atomising temperature 100°C lower when matrix modifier is used. The sensitivity of the method for Ag was 25% better with modifier. The detection limit, calculated in relation to the original solid sample, was 0.01 g/g with modifier.The results were systematically lower with matrix modifier, the mean value of recovery being 91.2% with modifier and 97.2% without. The ranges of the recovery values were noticeably different: from 84.5 to 99.5 with matrix modifier and from 63.4 to 110.2 without. The matrix modifier tended to even out the differences in the effects of geological matrices.

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Direkte Silberbestimmung in geologischem Referenzmaterial mit Hilfe der Graphitofen-AAS mit Matrixmodifikation (nach Auslaugen mit Königwasser)