Highly sensitive simultaneous determination of sulfonamide antibiotics and one metabolite in environmental waters by liquid chromatography–quadrupole linear ion trap–mass spectrometry

The present work describes the development of a highly sensitive analytical method based on liquid chromatography–quadrupole linear ion trap–mass spectrometry (LC–QqLIT–MS) for the determination of nine sulfonamide antibiotics and one N4-acetylated metabolite in environmental waters (wastewater, surface water and groundwater) and bottled mineral water. Special emphasis was devoted to the elimination of matrix components during solid-phase extraction (SPE) by the evaluation of three different extraction/purification strategies: single cartridges (Oasis HLB and Oasis MCX) and tandem (TD) extraction (combination of both). The method developed proved to be suitable for sulfonamide determination in all kinds of waters tested. The method was shown to be linear in a wide concentration range, with correlation coefficients higher than 0.999 for all compounds except for sulfadimethoxine (R2 0.997). The overall instrumental repeatability was satisfactory, with the exception of the metabolite (RSD 34%). Method limits of detection achieved for sulfonamides were in the range 0.01–1.13 ng L−1 and for the metabolite 0.08–461 ng L−1. Recovery rates were estimated at 500 ng L−1 spike level in the four water matrices selected. The highest recovery achieved in all matrices was that corresponding to the Oasis HLB cartridge. In environmental waters, recovery values obtained were higher than 61% for the surface water and, in general, higher than 90% for groundwater and wastewater. Bottled mineral water exhibited recovery rates higher than 92%, with the exception of sulfamethoxypiridazine (82%) and sulfapyridine (86%) In order to demonstrate the applicability of the developed method, several water samples were analyzed. Results evidenced the requirement for consideration of N4-acetylated metabolites of sulfonamides in environmental residue analysis to avoid the underestimation of removal rates of such pharmaceutical compounds during wastewater treatments.