Fully automated determination in the low nanogram per liter level of different classes of drugs of abuse in sewage water by on-line solid-phase extraction-liquid chromatography-electrospray-tandem mass spectrometry

The present work describes the first fully automated method, based on on-line solid-phase extraction (SPE)-liquid chromatography-electrospray-tandem mass spectrometry, developed for the determination of drugs of abuse (17 compounds and metabolites belonging to the classes of amphetaminics, cannabinoids, cocainics, opiates, and lysergics) in sewage waters. On-line SPE is performed by passing 5 mL of the water sample through a PLRP-s cartridge for analytes measured in positive ionization mode (all but cannabinoids) and through an Oasis HLB cartridge for analytes measured in negative ionization mode (cannabinoids). For unequivocal identification and confirmation two selected reaction monitoring transitions are registered per compound, thus achieving the four identification points requested by the European Union for banned substances. Quantitation is performed by the internal standard method, indispensable to correct for matrix effects. The main advantages of the method developed are high sensitivity (limits of determination between 0.69 and 5.97 ng/L), selectivity and reliability of results, minimum sample manipulation, full automation, and fairly high throughput (analysis time per sample is 2 x 35 min). As a part of the validation procedure, the method developed has been applied to the analysis of various influent and effluent samples from four Spanish sewage treatment plants.