Determination of seven drugs of abuse and their metabolites in surface and wastewater using solid-phase extraction coupled to liquid chromatography with high-resolution mass spectrometry.

A method based on liquid chromatography with electrospray ionization high-resolution mass spectrometry (Exactive Orbitrap) combined with solid-phase extraction using a strong cationic exchange mixed-mode sorbent has been developed for the determination of seven drugs of abuse, including two synthetic cathinones, as well as some of their metabolites in environmental water samples. The method provides low detection limits and a high confirmation power thanks to the diagnostic and two fragment ions monitored for each compound in high-resolution mass spectrometry, providing six identification points for each analyte. The clean-up step based on methanol in the extraction step adequately decreased the matrix effect, mainly for river and effluent water, and provided suitable process efficiency. Method detection and quantitation limits for environmental waters were at low nanogram per liter. The method was applied to analyze the samples of influent and effluent wastewater, as well as surface water. Codeine, methadone, and its metabolite were determined in all samples of wastewater and the metabolite of cocaine, benzoylecgonine, was found at the highest concentration.