Rapid chemical profiling of ecstasy tablets using portable near-infrared spectroscopy for forensic intelligence and...

Chemical profiling of illicit drugs has traditionally relied on laboratory-based techniques such as gas chromatography-mass spectrometry (GC-MS). Recent developments in portable drug testing devices have facilitated the decentralization of forensic capabilities, enabling field users to obtain rapid results. In this study, portable near-infrared (NIR) spectroscopy was evaluated for the chemical profiling of ecstasy tablets. A total of 668 tablets from 393 seizures made by Swiss law enforcement agencies were analyzed. Intra- and inter-seizure spectral variability was assessed using Euclidean distance, and a threshold value was defined to identify pairs of samples exhibiting sufficiently similar NIR profiles to be considered potentially linked. The results showed that NIR spectroscopy successfully distinguished intra- and inter-variability, with only 1.14% of inter-seizure comparisons falling below the selected threshold. Most NIR-based groupings were consistent with GC-MS chemical profiles, supporting the technique's ability to highlight spectral similarities and generate hypotheses of potential links between seizures for forensic intelligence purposes. As a further application, this study evaluates the use of NIR-based chemical profiling for early response in a drug checking context. Through a case study of eleven tablets that the drug checking service's NIR classification model failed to identify, we demonstrate the ability to link similar tablets of concern without prior knowledge of their composition. Comparing the spectra of newly analyzed specimens with previously flagged hazardous samples could enable the timely dissemination of alerts to consumers and public health authorities. The use of such rapid, non-destructive analytical methods could support more efficient decision making and contribute to harm-reduction efforts. Overall, this study supports portable NIR spectroscopy as a rapid screening approach for highlighting potential links at the pre-tableting formulation level in forensic intelligence and early-response applications.