Evaluation of ATR-FTIR, HPLC-DAD, GC-MS, and GC-IR for the analysis of 145 street drug samples from drug checking services (2025)

Drug checking services (DCS) are entities that allow recreational drug users to have street drug samples analyzed. Diverse analytical methods are applied for DCS, ranging from test strips to mass spectrometry (MS). This work evaluates the performance and utility of common methodologies used for DCS operating with off-site drug testing, while additionally assessing the potential of gas chromatography coupled to vapor phase infrared spectroscopy (GC-IR). Gas chromatography MS (GC-MS), GC-IR, and high-performance liquid chromatography with diode array detector (HPLC-DAD) were evaluated based on the analysis of 145 street drug samples obtained from two Swiss DCS. Additionally, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) was applied and is briefly discussed. A combined total of 245 analytes (including adulterants and cutting agents) were detected. GC-MS presented the greatest number of detected compounds, with a sensitivity of 96% compared with the sum of all analytes, followed by HPLC-DAD with 82%, while GC-IR showed limited sensitivity with 70%. GC-IR underperformed regarding the detection of low-abundant adulterants and of the main active ingredients in strongly adulterated samples. This study discusses the limitations and strengths of the evaluated methods in the specific context of DCS, while providing insights into the occurrence of false declarations (differing analytical results compared with alleged drug identity) and the distributions of adulterants and cutting agents in street drug samples. Based on our results, complementary approaches are considered the most valuable. Finally, the promotion of comprehensive guidelines regarding the quality and suitability of analytical methods for DCS would be highly desired. [Author's abstract]