Quantification of new psychoactive substances in Australian wastewater utilising direct injection liquid chromatography coupled to tandem mass spectrometry

The dynamic new psychoactive substances (NPS) market presents a great challenge for public health officers, law enforcement and analytical and forensic chemists. Wastewater analysis is a complementary tool in the ongoing surveillance of these compounds but the low doses, somewhat unknown metabolism and the different chemical classes have made analytical methods difficult to develop. The current study presents a direct injection method for the quantification of 32 NPS. These include a range of classes: phenethylamines (25C-NBOMe and 4-fluoroamphetamine), synthetic cathinones (3-methylmethcathinone, butylone, dibutylone, eutylone, methcathinone, N-ethylheptedrone, N-ethylhexedrone, N-ethylpentylone and pentylone), synthetic cannabinoid receptor agonists (5F-EMB-PICA, 5F-MDMB-PICA, 5F-MDMB-PINACA, AMB FUBINACA, MDMB-4en-PINACA, cumyl pegaclone and cumyl-5F-pegaclone), opioids (2-methyl AP-237, AP-238, brorphine, isotonitazene, metonitazene and protonitazene), benzodiazepines (clonazolam, etizolam, flualprazolam and flubromazolam), plant-based NPS (7-hydroxymitragynine and mitragynine) and dissociatives (2F-deschloroketamine, 2-oxo-PCE). The method was validated in terms of linearity, range, precision (interday and intraday), limit of detection and limit of quantification, while filtration losses and matrix effects were also examined. The method was applied to wastewater samples collected from New South Wales and Queensland over the 2021-22 New Year period, when recreational drug use was expected to increase. Three NPS were found: eutylone, clonazolam and etizolam, with eutylone having the highest mass loads.