Speciation Analysis of Thallium by Reversed-phase Liquid Chromatography - Inductively Coupled Plasma Mass Spectrometry

An inductively coupled plasma mass spectrometer (ICP-MS) was used as a liquid chromatographic detector for the speciation analysis of thallium in environmental samples. In this study, ionic thallium species, namely T1(I) and T1(III) were well separated by reversed-phase high performance liquid chromatography (RP-HPLC) with a C8-HPLC column as the stationary phase and 1 mmol L-1 tetrabutylammonium phosphate (TBAP), 2 mmol L-1 diethylenetriamine pentaacetic acid (DTPA) in 1% v/v methanol solution (pH 6) as the mobile phase. Effluent from the HPLC column was delivered to the nebulizer of the ICP-MS for the determination of thallium. The separation was complete in less than 3 min. Detection limit was 0.002 mu g L-1 for both T1(I) and T1(III) compounds based on peak height. The relative standard deviation of the peak areas for five injections of a mixture containing 1 mu g T1 L-1 was better than 3.4%. The concentrations of T1 compounds were determined in standard reference materials, including NIST SRM 1643e Trace Elements in Water and NRCC NASS-5 Open Ocean Seawater and water samples collected in Kaohsiung area, Taiwan. The HPLC-ICP-MS results of the reference samples agreed with the reference values. This method has also been applied to determine T1(1) and T1(III) compounds in custard apple (Annona squamosa) leaves collected from Chai-shan Mountain, Kaohsiung and Taitung City, Taiwan. The thallium species were quantitatively leached from the leaves with a 5 mmol L-1 DTPA in 100 mmol L-1 ammonium acetate solution in an ultrasonic bath during a period of 30 min. The HPLC-ICP-MS result that was obtained after the analysis of leaves sample showed a satisfactory agreement with the total thallium concentration obtained by ICP-MS analysis of completely dissolved sample.