Simultaneous determination of psychoactive drugs and their metabolites in aqueous matrices by liquid chromatography mass spectrometry

A multi-residue method was developed that allows for the simultaneous determination of psychoactive compounds such as opioids, tranquilizers, antiepileptics (primidone, carbamazepine plus two metabolites), the cocaine metabolite benzoylecgonine, the antidepressant doxepin, as well as the calcium channel blocker verapamil in raw and treated wastewater, surface water, groundwater, and drinking water. After solid-phase extraction with Oasis HLB at neutral pH, the analytes were detected by LC electrospray tandem MS in the positive ion mode. With a few exceptions relative recoveries of the analytes exceeded 70%. The limits of quantification were in the low ng/L range. Matrix effects were compensated by using appropriate deuterated or C-13-N-15-labeled surrogate standards. For raw and treated wastewater, concentration factors were lowered to reduce matrix effects. Most analytes (15 of 20) were found in raw and treated wastewater as well as in surface water, and hence, are presumably ubiquitously present in the environment. Antiepileptics, the opium alkaloids morphine and codeine, dihydrocodeine, the two tranquilizers oxazepam and temazepam, the opioid tramadol, doxepin, and verapamil were detected in STP discharges and German rivers at concentrations up to the Ag/L range. In drinking water, only carbamazepine, its metabolite 10,11-dihydroxy-10,11- dihydrocarbamazepine, and primidone were present at concentrations up to 0.020 Ag/L.