Determination of Tl(I) and Tl(III) by IC-ICP-MS and application to Tl speciation analysis in the Tl hyperaccumulator plant Iberis intermedia

Abstract

Speciation of thallium was investigated in a Tl hyperaccumulator plant, Iberis intermedia, by ion chromatography (IC) and size-exclusion chromatography (SEC) coupled with on-line ICP-MS detection. The leaves, stems and roots of the plant were extracted with a buffer solution (pH 6.2) containing DTPA and ammonium acetate. DTPA was used to complex unstable Tl(III) to form the stable Tl(III)–DTPA anionic complex. The two species, Tl(I) and Tl(III)–DTPA, were separated by using two separation mechanisms, anion exchange chromatography and SEC, with 100 mmol L⁻¹ ammonium acetate (pH 6.2) as eluant. The anion exchange chromatograms indicated that the chemical form of Tl present in extracts of both fresh and freeze-dried samples of the roots, stems and leaves is predominantly Tl(I), and this was confirmed by size-exclusion chromatography and electrospray mass spectromety.