Determination of trace amounts of aluminium in high-purity tin by electrothermal atomic absorption spectrometry

Abstract

A method is described for the determination of trace amounts of aluminium in high-purity tin by electrothermal atomic absorption spectrometry. The sample is decomposed in hydrochloric acid. The measurement is performed on an aqueous 0.05 mol l^–1 HCl solution and a chemical modifier is not used, so the method is simple and rapid. For the analysis of high-purity tin reference samples for aluminium in the concentration range 0.1–5.9 ppm, the results were in good agreement with the certified values. The relative precision of analysis is 10–20%, the measuring accuracy is within ± 5% and the sensitivity of the method is 26 pg per 0.0044 absorbance. Studies were carried out on the mechanism involving aluminium and tin. AlCl₃ and SnCl₂ are converted into Al(OH)₃ and Sn(OH)Cl, respectively, in the drying stage. In the ashing stage when the Al(OH)₃ is converted into Al₂O₃, no loss of aluminium is found, but a large amount of Sn(OH)Cl is evaporated and a small amount of Sn(OH)Cl is converted into SnO₂, which does not interfere in the measurement of aluminium.