Direct injection UPLC-MS/MS method for analysing 77 compounds including human biomarkers, illicit drugs, new psychoactive substances and metabolites in wastewater

Wastewater analysis technology has emerged as a promising tool for monitoring illicit drug consumption. However, the current reliance on the solid-phase extraction (SPE) pre-treatment method presents significant challenges for widespread adoption and high-throughput monitoring, as it consumes a large amount of time and labor as well as requires specialized instruments. This study has developed a direct injection (DI) technique for UPLC-MS/MS, enabling the detection of 77 compounds encompassing metabolites of human biomarkers, illicit drugs, and new psychoactive substances. The DI method underwent rigorous optimization and validation, demonstrating a lower limit of quantitation (LLOQ) ranging from 1 ng L^–1 to 100 ng L^–1 and a limit of detection (LOD) ranging from 0.5 ng L^–1 to 80 ng L^–1. The SPE method comprising two common SPE cartridges and the DI method were compared in terms of matrix effects, recoveries, and accuracies through analyzing spiked wastewater samples. The DI method exhibited superior capability in detecting a wider range of compounds while being more time-efficient, and it also significantly demonstrated a better recovery, lower matrix effect, and lower relative error in spiked samples. Real wastewater samples from 25 wastewater treatment plants (WWTPs) were analyzed using this method. This study expanded the targets species of wastewater analysis by DI method and provided practical strategies for conducting large-scale drug monitoring.