Profiling and classification of illicit heroin by ICP-MS analysis of inorganic elements

Nineteen inorganic elements (Ag, As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, P, Pb, Se, Sb, Th, Tl, U, V and Zn) in heroin samples were determined using inductive coupled plasma mass spectrometry (ICP-MS). After Wilcoxon-Mann-Whitney test and correlation analysis, 10 element contents (P, V, Cr, Ni, Cu, Zn, As, Se, Pb, U) and 7 element ratios (U/Ba, Ba/Pb, Cd/Mn, Co/Ni, V/Cr, P/V, Cd/V) were found to be evidently different between heroin samples from "Golden Crescent" and "Golden Triangle". Based on the data set of these 17 variables in 150 authentic heroin samples, classification of origins was successfully achieved utilizing principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). By comparison experiment on 907 unknown samples, the developed discriminant model was proven to be consistent with the widely used organic profiling method, and meanwhile the time consumed per sample was markedly saved, which facilitates high throughput screening in routine analysis.