Investigations of reactions involved in electrothermal atomic absorption procedures: Part 11. A theoretical and experimental investigation of factors influencing the determination of tin

Abstract

Factors of importance for the determination of tin by graphite-furnace atomic absorption spectrometry have been investigated. Losses of tin during the drying and ashing stages were monitored by use of radioactivity measurements. It was found that tin could be lost at 100°C when ordinary graphite or glassy carbon surfaces were used. However, if the sample was dispensed into a droplet of ammonia, no losses occurred until 800°C, independent of the graphite surface, because tin is stabilized as SnO 2 (s,l) and chloride is removed as ammonium chloride. High-temperature equilibrium calculations indicate that tin forms volatile oxides, halides and sulphides which are stable up to relatively high temperatures. As is shown experimentally with commercial non-isothermal atomizers, these molecules might be removed from the system before their decomposition temperature is reached. A recently developed constant-temperature furnace was used to vaporize the sample into an environment of high and constant temperature, in which interference effects from chlorine and sulphur were minimized, as predicted by theory.