Optimization of antibiotic analysis in water by solid-phase extraction and high performance liquid chromatography-mass spectrometry/mass spectrometry

This paper describes the development of an optimized method based on solid-phase extraction (SPE) followed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS) for the simultaneous analysis of ten antibiotic compounds including tetracyclines, sulfonamides, macrolides and quinolones. LC-MS/MS sensitivity has been optimized by alterations to both LC and MS operations. Of the two high resolution columns tested, Waters Symmetry C₁₈ endcapped and Agilent Zorbax Bonus-RP, the latter was found to show better performance in producing sharp peaks and clear separation for most of the target compounds. Optimization of the MS fragmentation collision and cone energy enhanced the peak areas of the target analytes. The recovery of the target compounds from water samples was most efficient on Waters Oasis HLB SPE cartridge, while methanol was shown to be the most suitable solvent for desorbing the compounds from SPE. In addition, acidification of samples prior to SPE was shown to enhance the recovery of the compounds. To ensure a satisfactory recovery, the flow rate through SPE should be maintained at ≤10mLmin^-1. The method was successfully applied to the analysis of antibiotics from environmental water samples, with concentrations being <LOD in tap water, between <LOD to 28ngL^-1 in river water and between <LOD to 230ngL^-1 in sewage effluent.