More and more events, such as the summer music festivals, are considering the

possibilities for implementing on-site testing of psychoactive drugs in the context of

prevention and harm reduction. Although the on-site identification is already

implemented by plenty of drug checking services, the required rapid quantitative

dosing of the composition of illicit substances is still a missing aspect for a successful

harm reduction strategy at events. In this paper, an approach is presented to identify

white powders as amphetamine, cocaine, ketamine or others and to estimate the

purity of the amphetamine, cocaine and ketamine samples using spectroscopic

techniques hyphenated with partial least squares (PLS) modelling. For identification

purposes, it was observed that mid-infrared spectroscopy hyphenated with

PLS-discriminant analysis allowed the distinction between amphetamine, cocaine,

ketamine and other samples and this with a correct classification rate of 93.1% for an

external test set. For quantitative estimation, near-infrared spectroscopy was more

performant and allowed the estimation of the dosage/purity of the amphetamine,

cocaine and ketamine samples with an error of more or less 10% w/w. An easily

applicable, practical and cost-effective approach for on-site characterisation of the

majority of the psychoactive samples encountered in Belgian nightlife settings based

on IR spectroscopy was proposed.