Trace Element Analysis of Cigarette and Cigarette Ash by ICP-MS and Its Application for Forensic Discrimination

Abstract

The analysis of trace elements in cigarettes and cigarette ash using ICP-MS was applied to the forensic discrimination of cigarette samples from different sources. Seven boxes of cigarettes were purchased from 6 different brands; 1 – 5 of 20 sticks in each box were used for experiments. Approximately 50 – 100 mg of cigarette or 20 mg of cigarette ash was taken from a stick, accurately weighed and dissolved into a mixture of 1.5 mL nitric acid and 0.5 mL hydrogen peroxide by heating in a microwave oven. After cooling to room temperature, it was diluted to 20 mL, centrifuged and the supernatant obtained was subjected to elemental analysis using ICP-MS. Rhodium was used as an internal standard for quantitative analysis. The mass spectra of the 7 different cigarettes demonstrated that they contained 11 elements (Cu, Zn, Rb, Sr, Mo, Cd, Ba, La, Ce, Nd and Pb). These elements in NIST 1515 (Apple Leaves) could be determined with RSDs (relative standard deviations) from 0.8 % for Cu to 6.0 % for Mo and with satisfactory good agreement with the certified or reference values except for Cd. Measured values for cigarette samples taken from 5 different positions within cigarette stick provided RSDs from 2.4 % for Cu to 12.9 % for Ba; these values were much smaller than most of those among cigarettes from different boxes. Comparisons of the elemental concentrations, except for Zn and Pb, made it possible to distinguish all of the 21 possible pairs among 7 different cigarettes. The concentrations of trace elements in cigarette ash were calculated using the weight ratio (0.21 ± 0.01) of ash to the original cigarette and measured values of trace elements in the cigarette. The measured values for cigarette ash showed good agreement with the calculated ones, except for Cd and Pb, which exhibited significantly lower measured values in ash than the calculated ones.