Chemometric assessment of electronic cigarettes based on the ICP-MS determination of multiple heavy metal concentrations

Abstract

To elucidate the concentrations of heavy metal elements in commercially available electronic cigarettes and improve quality assessment. Inductively coupled plasma-mass spectrometry (ICP-MS) coupled to chemometrics was used to determine the concentrations of Cr, Ni, As, Cd, Sn, Sb, Hg, and Pb in the e-liquids and aerosols derived from 32 electronic cigarettes sold commercially under six brand names. The e-liquids contained: 4.858 to 274.658 (Cr), 17.292 to 3068.375 (Ni), 3.217 to 29.867 (As), 0.225 to 24.717 (Cd), 0.783 to 17.042 (Sn), 0.658 to 36.033 (Sb), 0.658 to 187.592 (Hg), and 2.458 to 17.417 (Pb) ng g⁻¹. The aerosol samples contained: 276.075 to 3333.175 (Cr), 72.908 to 1150.183 (Ni), 4.567 to 86.958 (As), 0.400 to 12.842 (Cd), 1.092 to 32.142 (Sn), 0.976 to 10.633 (Sb), 3.483 to 234.708 (Hg), 27.833 to 849.100 (Pb) ng 100 puffs⁻¹. The recovery of heavy metals ranged from 99.1% to 112.4% in the e-liquids and from 87.3% to 116.6% in the aerosols, with RSD values below 10%. Hierarchical cluster analysis grouped the e-liquids into eight clusters, and the aerosols into five, indicating differences between products within brands and between different brands. Orthogonal partial least squares discriminant analysis coupled with variable importance in projection (VIP > 1) identified As and Sb as the primary heavy metals causing differences between the e-liquids, while differences between the aerosols were caused by Hg, As, Pb, Cd, and Cr. The use of chemometric methods yields a greater depth of information that will support improvements to the quality control of e-cigarette products and the assessment of their potential risk to human health.