Determination of illicit drugs in aqueous environmental samples by online solid-phase extraction coupled to liquid chromatography–tandem mass spectrometry

• Online SPE LC–MS/MS method was developed to identify 10 illicit drugs.
• Matrix effects can be reduced by online washing steps.
• Availability of illicit drugs in China has been reported.
• Caffeine, cotinine, and paraxanthine were detected with high concentrations.

In this study, a fully automated analytical method, based on online solid phase extraction coupled to liquid chromatography-triple quadrupole tandem mass spectrometry (online SPE-LC-MS/MS), has been developed and optimized for the quantification of 10 illicit drugs and metabolites in environmentally aqueous samples collected from China. The particular attention was devoted to minimize the matrix effects through a washing step, which washed out the interferences effectively and helped to reduce the matrix effect significantly. The key advantages of the method are high sensitivity, selectivity and reliability of results, smaller sample manipulation, full automation, and fairly high throughput. The whole procedure was then successfully applied in the analysis of various surface water and wastewater effluents samples. Pseudoephedrine have been detected at trace levels (several tens ng L−1 or less), while MDA, MDMA, benzoylecgonine and methadone were below the LOQ in all samples. Caffeine, cotinine and paraxanthine, which may be derived from medicines and foods, were detected with the highest frequencies and concentrations.