Determination of pharmaceuticals in water samples by (DI)UHPLC-MS/MS

Abstract

This study evaluates a direct sample injection methodology for the simultaneous identification and quantification of 16 human pharmaceuticals. Water samples were analysed by ultra-high performance liquid chromatography coupled to tandem mass (UHPLC-MS/MS) using a triple quadrupole analyser (QqQ). Overall satisfactory recoveries were obtained from sixteen compounds in a total of nine spiked samples (2 surface waters (SWs), 3 effluent wastewaters (EWWs) and 4 influent wastewaters (IWWs)). The quantitative validation has been performed with samples that have not undergone major manipulation except for a dilution step for EWW and IWW samples in order to adjust them to the instrumental sensitivity. As a result, the concentrations were 100 ng/L for SWs, 200 ng/L for EWWs and 500 ng/L for IWWs. The majority of compounds could be satisfactorily validated at these concentrations. To assure reliable identification, three transitions per compound were acquired and used along with retentions times as evidence to confirm the identity and the magnitude of any contaminant detected. The presence of all compounds could be successfully confirmed except for Azithromycin in SW samples. In addition, available isotope-labelled internal standards (ILIS) were added to the samples to compensate matrix effect (ME) which was more notorious for IWW samples and manifested, almost exclusively, as signal suppression.