Drugs of abuse and their metabolites in waste and surface waters by liquid chromatography-tandem mass spectrometry

A solid-phase extraction and liquid chromatography-tandem mass spectrometry (SPE/LC-MS-MS) method was developed and validated for the simultaneous determination of nicotine, five drugs of abuse (morphine, cocaine, codeine, methadone, and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine) and four metabolites (dihydrocodeine, 6-acetylmorphine, 11-nor-carboxy-Δ(9)-tetrahydrocannabinol, and benzoylecgonine) in water samples. A Fused-Core™ particle column was used as an alternative to sub-2-μm particles in chromatographic separations to work with low backpressures and high efficiencies in short analysis times. Drugs were extracted from waste and surface water with SPE using Oasis MCX cartridges. Electrospray (ESI) in positive and negative mode and tandem MS selected reaction monitoring mode were used for identification and quantification. Calibration by linear regression analysis with deuterated internal standards was used to compensate the matrix effects. Limits of detection were found as low as 0.5-1 ng/L (surface water) and 1-50 ng/L (wastewater). The method was applied to the analysis of different kinds of samples. Wastewater from a sewage treatment plant was collected from three sampling points (after primary, secondary, and tertiary treatments) for a week. The analysis of the samples revealed a significant presence of these drugs in samples from primary treatments, where maximum concentrations of nicotine (1105 ng/L) and benzoylecgonine (3336 ng/L) were found. Most of the compounds showed values between <LOQ and 52 ng/L after tertiary treatment. When surface waters from the Ebro River were analyzed, only benzoylecgonine showed levels between 19 and 35 ng/L.