Multi-residue analysis of drugs of abuse in wastewater and surface water by solid-phase extraction and liquid chromatography–positive electrospray ionisation tandem mass spectrometry

A new-multi residue method was developed for the environmental monitoring of 65 stimulants, opiod and morphine derivatives, benzodiazepines, antidepressants, dissociative anaesthetics, drug precursors, human urine indicators and their metabolites in wastewater and surface water. The proposed analytical methodology offers rapid analysis for a large number of compounds, with low limits of quantification and utilises only one solid-phase extraction–ultra performance liquid chromatography–positive electrospray ionisation tandem mass spectrometry (SPE–LC–MS/MS) method, thus overcoming the drawbacks of previously published procedures. The method employed solid phase extraction with the usage of Oasis MCX sorbent and subsequent ultra performance liquid chromatography–positive electrospray ionisation tandem mass spectrometry. The usage of a 1.7 μm particle size column (1 mm × 150 mm) resulted in very low flow rates (0.04 mL min−1), and as a consequence gave good sensitivity, low mobile phase consumption and short retention times for all compounds (from 2.9 to 23.1 min). High SPE recoveries (>60%) were obtained for the majority of compounds. The mean correlation coefficients of the calibration curves were typically higher than 0.997 and showed good linearity in the range 0–1000 μg L−1. The method limits of detection ranged from 0.1 ng L−1 for compounds including cocaine, benzoylecgonine, norbenzoylecgonine and 2-oxo-3-hydroxy-LSD to 100 ng L−1 for caffeine. Method quantification limits ranged from 0.5 to 154.2 ng L−1. Intra- and inter-day repeatabilities were on average less than 10%. The method accuracy range was within −33.1 to 30.1%. The new multi-residue method was used to analyse drugs of abuse in wastewater and river water in the UK environment. Of the targeted 65 compounds, 46 analytes were detected at levels above the method quantification limit (MQL) in wastewater treatment plant (WWTP) influent, 43 in WWTP effluent and 36 compounds in river water.