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

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.