Determination of Three Lead Species in Tobacco and Tobacco Products by HPLC-ICP-MS

A method for the determination of inorganic leadPb(Ⅱ), trimethyl lead (TML) and triethyl lead (TEL) in tobacco and tobacco products by HPLC-ICP-MS was established. After the tobacco sample was crushed, 15 mL of the mixture (mobile phase) of 1 mmol·L^-1 sodium 1-pentanesulfonate solution and methanol with volume ratio of 60:40 was added. The sample was extracted by ultrasound at 40℃ for 20 min and then centrifuged. The supernatant was filtered with a 0.22 μm filtering membrane. The contents of the three lead species in the filtrate were determined by HPLC-ICP-MS. Tobacco samples were mixed with nitric acid and 30% hydrogen peroxide solution, and digested by microwave under the programmed temperature. The digestion solution was diluted with water and the total amount of lead was determined by ICP-MS. In HPLC analysis, the three lead species adsorbed on Eclipse plus C₁₈ revesed-phase chromatographic column were isocratically eluted at a flow rate of 1.0 mL·min^-1 within 8 min. In ICP-MS analysis, three lead isotopes, including ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb, were simultaneously monitored and their total content was used for quantification. The results showed that the linearity relationships between mass concentrations of the three lead species and their respective MS response values were kept in the range of 0.5-50.0 μg·L^-1, with detection limits (3S/N) in the range of 0.33-0.47 μg·L^-1. The spiked recovery test was made on actual samples at the 3 concentration levels, giving results of recovery in the range of 81.9%-96.5%, and RSDs (n=6) of the determined values ranged from 5.3% to 9.6%. The prescribed method was applied to the analysis of tobacco samples as well as cigarette samples, no organic lead was detected in the 2 kinds of samples. Pb(Ⅱ) was the main form of lead, with its content as low as 1.53-5.08 μg·g^-1. The content of lead in lower, middle and upper parts of tobacco samples decreased gradually. The lead content in cigarette samples was basically the same as that in tobacco samples. Sum of content of the three lead species accounted for 74.3%-84.6% of total lead.