Multiresidue trace analysis of sulfonamide antibiotics and their metabolites in soils and sewage sludge by pressurized liquid extraction followed by liquid chromatography–electrospray-quadrupole linear ion trap mass spectrometry

The present study describes the development, validation and a practical application of a fully automated analytical method based on pressurized liquid extraction (PLE) followed by solid-phase extraction-liquid chromatography–tandem mass spectrometry (SPE-LC–MS/MS) for the simultaneous determination of 22 sulfonamides, including five acetylated metabolites, in sewage sludge and soil samples. Both matrix matched calibration curves and standard calibration curves were built in order to evaluate the potential matrix effects during analysis, and different internal standards were used to compensate these effects during quantification. The recovery efficiencies were found to be 60–130% for the majority of the sulfonamides in both matrices and at two spike levels. The intra-day and inter-day precisions, expressed by the relative standard deviation (RSD), were below 23%. The method limits of detection (MLODs) achieved were in the range 0.03–2.23 ng g−1 for sewage sludge and 0.01–4.19 ng g−1 for soil samples. The methodology was applied to evaluate the occurrence of the target sulfonamides in several sewage sludge and soil samples taken in different wastewater treatment plants (WWTPs) and agricultural areas. Results confirmed the wide presence of sulfonamides in both matrices, being sulfathiazole and sulfamethazine the sulfonamides most frequently detected in sewage sludge and soil samples, respectively. Maximum concentrations corresponded to sulfamethazine in both cases (139.2 ng g−1 and 8.53 ng g−1 for sewage sludge and soils respectively). Levels were generally lower in soils. Three of the five acetylated metabolites were detected in sewage sludge and two of them in soils, at concentrations not higher than 9.81 ng g−1.