Chemometrics and infrared spectroscopy – A winning team for the analysis of illicit drug products

Abstract Spectroscopic techniques such as infrared spectroscopy and Raman spectroscopy are used for a long time in the context of the analysis of illicit drugs, and their use is increasing due to the development of more performant portable devices and easy application in the context of harm reduction through drug checking or onsite forensic analysis. Although these instruments are routinely used with a spectral library, the importance of chemometric techniques to extract relevant information and give a full characterisation of samples, especially in the context of adulteration, is increasing. This review gives an overview of the applications described in the context of the analysis of illicit drug products exploiting the advantages of the combination of spectroscopy with chemometrics. Next to an overview of the literature, the review also tries to emphasize the shortcomings of the presented research papers and to give an incentive to what is needed to include chemometrics as a part of the daily routine of drug checking services and mobile forensic applications.