Multianalyte method for the determination of pharmaceuticals in wastewater samples using solid-phase extraction and liquid chromatography-tandem mass spectrometry

A fast and sensitive multianalyte/multiclass high-performance reversed-phase liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous analysis of 89 pharmaceuticals in influent and effluent wastewater samples. The method developed consists of solid-phase extraction (SPE) using a hydrophilic-lipophilic-balanced polymer followed by LC-MS/MS with electrospray ionization in both positive mode and negative mode. The selected pharmaceuticals belong to different classes-analgesic/anti-inflammatory drugs, antibiotics, antiepileptics, beta-adrenoceptor-blocking drugs, lipid-regulating agents, statins, and many others. The influence of the mobile phase composition on the sensitivity of the method, and the optimum conditions for SPE in terms of analyte recovery were extensively studied. Chromatographic separation was performed on an Atlantis T3 (100 mm x 2.1 mm, 3-mu m) column with a gradient elution using methanol-0.01 % v/v formic acid as the mobile phase in positive ionization mode determination and methanol-acetonitrile-1 mM ammonium formate as the mobile phase in negative ionization mode determination. Recoveries for most of the compounds ranged from 50 to 120 %. Precision, expressed as relative standard deviations, was always below 15 %, and the method detection limits ranged from 1.06 ng/L (4-hydroxyomeprazole) to 211 ng/L (metformin). Finally, the method developed was applied to the determination of target analytes in wastewater samples obtained from the Psyttalia wastewater treatment plant, Athens, Greece. Although SPE of pharmaceuticals from wastewater samples and their determination by LC-MS/MS is a well-established technique, the uniqueness of this study lies in the simultaneous determination of a remarkable number of compounds belonging to more than 20 drug classes. Moreover, the LC-MS/MS method has been thoroughly optimized so that maximum sensitivity is achieved for most of the compounds, making the proposed method a valuable tool for pharmaceutical analysis in influent and effluent wastewater at the sub-nanogram per liter level.