Portable Raman spectroscopy applied to the study of drugs of abuse

Abstract

The use of drugs of abuse has grown significantly in recent decades. In forensic chemistry, methods of identifying and characterizing illicit drugs contribute to the interests of researchers, experts, and public security authorities. Among existing methods, portable Raman spectroscopy is notable for performing rapid, non-destructive, and highly selective analysis in the laboratory or on-site. When the resulting spectral data are paired with chemometric tools, methods of exploratory analysis and multivariate calibration can be developed. Thus, this work describes the application of Raman spectroscopy associated with principal component analysis (PCA) and interval principal component analysis (iPCA) to assessing trends in samples of cocaine (n = 40), crack (n = 33), and their main adulterants (n = 5) and diluents (n = 5), tablets of ecstasy (n = 14), designer drugs papers (n = 27), and alcoholic solutions adulterated with benzodiazepines (alprazolam and diazepam). In addition, competitive adaptive reweighted sampling (CARS) combined with partial least squares (PLS) regression (CARSPLS) was used to quantify adulterants (benzocaine, lidocaine, and procaine) in binary mixtures with crack (n = 21) and solutions of cachaça adulterated with bromazepam (n = 11).