Determination of antibiotics in aquatic environment by solid-phase extraction followed by liquid chromatography–electrospray ionization mass spectrometry

A robust and sensitive solid-phase extraction followed by liquid chromatography–electrospray ionization mass spectrometric (LC–ESI-MS) method for determination of antibiotics viz., fluoroquinolones, sulfamethoxazole, trimethoprim and cephalosporines in surface waters was developed. The sample recoveries on Oasis HLB cartridges were found to be >80%. Identification was carried out by LC–ESI-MS/MS. The positive ion ESI mass spectra containing the peaks of quasimolecular ions [M+H]+ allowed the determination of molecular masses whereas the fragment ions obtained by MS/MS of [M+H]+ ions permitted the structural assignment. Quantification was carried out by selective ion monitoring (SIM) using the quasimolecular ions [M+H]+ of the parent compounds. The detection and quantification limits were found to be in the range of 0.6–8.1 and 2.0–24.0 μg/L. The surface waters of different lakes and tanks of Hyderabad, India were found to contain a few antibiotics.