Solid-phase extraction–high-performance liquid chromatography–ion trap mass spectrometry for analysis of trace concentrations of macrolide antibiotics in natural and waste water matrices

A method using solid-phase extraction (SPE) combined with high-performance liquid chromatography–ion trap tandem mass spectrometry (LC–MS–MS) has been developed for determination of trace concentrations of erythromycin-H2O (ETM-H2O), roxithromycin (RTM) and tylosin (TLS) in natural and waste water matrices. These macrolides (MLs) were extracted from water samples using Oasis HLB cartridges, and the average recovery was 93.6±8.6, 92.1±10.0, and 94.3±8.9% for ETM-H2O, RTM and TLS in surface water, respectively. For water from the influent of a wastewater treatment plant (WWTP), the average recovery was 84.8±14.0, 83.2±13.1, and 86.1±13.4% for ETM-H2O, RTM and TLS, respectively. Method detection limits in a natural water matrices were 0.07, 0.03, and 0.05 μg/l for ETM-H2O, RTM, and TLS, respectively. Fragment or product ions from MS spectra using in-source collision-induced dissociation and MS–MS spectra have been identified. The accuracy and day-to-day variation of the method fell within acceptable ranges. The method was evaluated by studying the occurrence of the three macrolides on a river and a WWTP in northern Colorado. None of the antibiotics were detected in the stream except immediately downstream of a WWTP, a result consistent with their presence in the influent and effluent of the treatment facility.