Direct analysis of barium, calcium, potassium, and manganese concentrations in tobacco by laser-induced breakdown spectroscopy

This work deals with method development for the direct measurement of Ba, Ca, K, and Mn concentrations in tobacco by laser-induced breakdown spectroscopy (LIBS). Cigarette and tobacco samples from different regions of Brazil were freeze-dried and cryogenically ground for 10 min. Pellets containing 0.5 g of the ground material were prepared by applying 10 T cm(-2) pressure for 5 min in a cylindrical die set. Accurate determination of concentrations was achieved via comparison with calibration data. Calibration standards were prepared from a selected milled tobacco sample either diluted with high-purity cellulose or spiked with increasing amounts of standard solutions of the analyte, followed by freeze-drying for 48 h and cryogenic mill homogenization. After acid decomposition, inductively coupled plasma optical emission spectroscopy (ICP OES) was used to determine the mass fraction of each analyte in the calibration standards. Using the proposed method, various tobacco samples were analyzed by LIBS; the results showed a concentration range of 70-120, 25,000-30,000, 30,000-40,000, and 120-250 mu g g(-1) for Ba, Ca, K, and Mn, respectively. The accuracy of the method was checked by the analysis of certified reference materials and by comparison of the results with obtained by ICP OES after acid decomposition. The results of Student's t-test showed 95% confidence level, indicating that the proposed LIBS method can be used for the direct analysis of tobacco. (C) 2016 Elsevier B.V. All rights reserved. (AU)