Multiresidual analysis of emerging amphetamine-like psychoactive substances in wastewater and river water

Besides the common illicit drugs, such as cocaine, heroin, and marijuana, there is a growing concern about the use of modern “designer drugs” that have emerged in large numbers over the past few years. In this work, a sensitive and selective method for simultaneous determination of 25 synthetic amphetamine-like psychoactive compounds, including amphetamine, sympathomimetic substituted amphetamines, synthetic cathinones and ketamine, in raw wastewater (RW), secondary effluent (SE) and river water was developed. Samples were enriched by solid-phase extraction (SPE) on mixed-mode reversed-phase/strong cation-exchange sorbent (Oasis MCX) and analysed by reversed-phase liquid chromatography coupled to electrospray ionisation tandem mass spectrometry (LC-MS/MS). The target compounds were separated on a Synergi Polar column and detected using multiple reaction monitoring (MRM) in positive ionisation mode. Accurate quantification was achieved by using several deuterated analogues as surrogate standards. Careful optimisation and validation of the procedure resulted in a reliable determination of all target analytes in low ng/L range for all matrices, which makes the method suitable for the application in wastewater-based epidemiology. The method was applied for assessment of selected compounds in municipal wastewater and river water from Croatia. It was shown that most of the wastewater samples contained detectable levels of the well-known synthetic illicit drugs, amphetamine and 3,4-methylenedioxy-methamphetamine (MDMA) (concentrations up to 545 ng/L and 55 ng/L in RW, respectively), as well as ephedrine (up to 108 ng/L) and pseudoephedrine (up to 698 ng/L), which are used as ingredients of popular over-the counter cough and cold medications. Other target amphetamine-like psychoactive substances, recently reported for their potential abuse, were detected only occasionally and in low concentrations (<10 ng/L).