Improved thallium hydride generation using continuous flow methodologies

Abstract

The use of continous flow vapour generation to improve the determination of thallium by atomic spectrometry has been investigated. Attempts to generate volatile organothallium compounds were unsucessful but using sodium tetrahydroborate a volatile thallium species was produced. Evidence was obtained to suggest that the vapour phase species was thallium(I) hydride, TlH. At room temperature noisy signals were obtained, but when the reaction manifold was chilled to 0 °C the signals were far more stable. Cooling did not significantly change the sensitivity. A characteristic concentration of 4 ng cm^–3 was obtained for continous flow vapour generation determination of thallium by atomic absorption spectrometry (AAS). This is a 1500-fold improvement on the previous sensitivity for batch vapour generation AAS. Continous vapour generation also appears to eliminate any serious interferences from other hydride-forming elements. Flow injection of nitric acid between samples was used to remove memory effects.