Simple flow injection spectrofluorimetric method for speciation of thallium

Abstract

A flow injection configuration is proposed for the determination of Tl^I and Tl^III individually and for mixtures of both analytes. The method allows speciation and fluorimetric detection of thallium in flowing solutions. Thallium(I) is determined by measuring its fluorescence in an HCl medium (λ_ex= 227 nm; λ_em= 419 nm). The determination of Tl^III is based on the rapid reduction of this ion by thiourea with the concomitant formation of fluorescent Tl^I. The inclusion of a selection valve in the manifold configuration allows the successive determination of the two ions. Linear calibration graphs were obtained between 5.0 × 10^–8 and 1.0 × 10^–5 mol l^–1 of Tl^I and between 1.0 × 10^–7 and 1.0 × 10^–5 mol l^–1 of Tl^III. The applicability of the method was demonstrated by investigating the effect of potential interferents and by the analysis of synthetic samples. The method was successfully applied to the determination of thallium in soils and zinc ores.