Simultaneous determination of seven residual pharmaceuticals in wastewater by solid-phase extraction and liquid chromatography coupled to tandem mass spectrometry with a switching ionization mode

A sensitive and highly selective method has been developed for the simultaneous determination of seven residual pharmaceuticals (paracetamol, chloramphenicol, salicylic acid, prednisone acetate, indomethacin, fenofibrate, and simvastatin) in wastewater influent and effluent. Samples were enriched by solid-phase extraction (SPE) and analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in a negative and positive switching ionization mode. Recoveries of individual pharmaceuticals in the ranges of 71.8-101.2% and 61.3-99.4% were obtained in the spiked samples of purified water and effluent matrices, respectively, at three concentration levels. Method detection limits were in the range of 1.293-36.95 ng L-1 and 0.6614-18.67 ng L-1 for the wastewater influent and effluent samples, respectively, while method quantification limits were in the range of 4.313-123.1 ng L-1 and 2.205-62.23 ng L-1 for the wastewater influent and effluent samples, respectively. The instrumental precision, calculated as relative standard deviation, ranged from 0.9 to 7.2%. The developed method was successfully applied to the analysis of wastewater samples from a wastewater treatment plant in Shenyang.