Simultaneous determination of new psychoactive substances and illicit drugs in sewage: Potential of micro-liquid chromatography tandem mass spectrometry in wastewater-based epidemiology.

Wastewater-based epidemiology (WBE) can give valuable light on the extent and actual use of new psychoactive substances (NPS). In this work, a fully validated methodology for the simultaneous determination of illicit drugs and NPS in wastewater by solid-phase extraction followed by UHPLC-MS/MS has been developed. The small sample volume (5 mL) required for analysis is of high interest, especially when performing large sampling campaigns involving many locations of different geographical origin, as it has been performed in the past. The method was applied to wastewater samples from different European locations and permitted the simultaneous monitoring of conventional drugs and NPS. Cocaine, amphetamine, MDMA, methamphetamine and ketamine were found in all wastewater samples, and several NPS (dipentylone, butylone, mephedrone, methedrone and methylone) were observed in some of the samples monitored. It is noteworthy that dipentylone was detected in wastewater for the very first time. Furthermore, a detailed comparison of micro liquid chromatography (μLC) and UHPLC, both coupled to tandem mass spectrometry, in terms of sensitivity and reproducibility has been made for the first time in the application field of WBE. An average increase factor of 14 (mass normalized data) was observed in sensitivity for μLC-MS/MS. The overall method performance was also compared (un-normalized data), and an average increase sensitivity factor of 4.5 was observed for μLC-MS/MS. However, large deviations in retention time (up to 0.4 min) affected the reproducibility and robustness of the μLC-MS/MS method when it was applied to wastewater analysis. Although in this work μLC-MS/MS was strongly influenced by the amount of matrix loaded in the separation device, its enhanced sensitivity and promotion of green chemistry (faster analysis time and less solvent consumption) allow to expect improved future applications, especially when analytes are present at very low concentrations.