Seized party drugs: New substances, combination mixtures, and polydrug use.

Party drugs are frequently used in social settings such as festivals. The changing dynamics of the party scene and drug market require up-to-date information on current drug use to support law enforcement, public health and policymakers. This study provides an overview of psychoactive substances seized at 2 international dance festivals in Belgium. In total, 1151 samples were analysed on-site using ATR-FT-IR and Raman. Selected samples were confirmed with GC-MS and quantified using GC-FID. Overall, 28 different psychoactive substances were registered in various physical forms, predominantly ecstasy-like tablets (44.3 %) and powders (34.1 %). MDMA remains the most prevalent drug, followed by cocaine and ketamine. In addition, 7 different types of synthetic cathinones (mainly MMC and CMC analogues) were detected. Notably, 33 "pink powder" samples, commonly referred as "pink cocaine", were analysed, revealing 16 distinct combinations in their composition. A new phenomenon involves colored liquids, often containing combinations of 2 or more synthetic drugs, such as amphetamine analogues and synthetic cathinones. Based on the analysis results, it can be concluded that there is a diversification of the drug market by the detection of 28 psychoactive substances used at a party scene. Additionally, alongside the rise of polydrug formulations, users take drugs with diverse pharmacological effects, including stimulants ("uppers"), sedatives ("downers") and psychedelics. The majority of the substances had high purity and were identified on-site using 2 complementary spectroscopic techniques with optimized settings and up-to-date libraries. The on-site detection of polydrug formulations (in powders, tablets and liquids) and low-dosed psychoactive substances (< 10 % w/w) is challenging, resulting in the necessity of lab confirmation for unambiguous identification.