Speciation analysis of thallium in tobaccos using 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 tobacco and cigarette ash samples. In this study, ionic Tl species, namely Tl(I) and Tl(III) were well separated in less than 2 min by reversed-phase high performance liquid chromatography (RP-HPLC). The stationary and mobile phases were C8 column and 7 mmol L−1 tetrabutylammonium phosphate (TBAP), 6 mmol L−1 diethylenetriamine pentaacetic acid (DTPA) in 2% (v/v) methanol solution (pH 5) respectively. Effluent from the HPLC column was delivered to the nebulizer of the ICP-MS for the determination of Tl. Detection limit was 0.003 ng mL−1 for both Tl(I) and Tl(III) compounds based on peak height. The relative standard deviation of peak areas for five injections of a mixture containing 1 ng Tl mL−1 each species was better than 1%. The Tl species were quantitatively leached from the tobacco and the ash into a solution of 5 mmol L−1 DTPA in 100 mmol L−1 ammonium acetate with/or without HF in an ultrasonic bath during a period of 20 min. The addition of HF improved the extraction of Tl from the ash sample. The extraction efficiency of Tl from tobacco was in the range 98-110%. Speciation analysis by HPLC-ICP-MS on tobacco samples showed a satisfactory agreement with the total Tl concentration obtained by ICP-MS analysis of completely dissolved samples. Tl(I) was the only detectable Tl species in tobacco samples analyzed, however both Tl(I) and Tl(III) were present in the cigarette ash.