Application of fully automated online solid phase extraction-liquid chromatography-electrospray-tandem mass spectrometry for the determination of sulfonamides and their acetylated metabolites in groundwater

The present study describes an automated methodology based on a liquid chromatography-electrospray, tandem mass spectrometry method combined with online solid phase extraction (online SPE-LC-ESI-MS/MS) for the simultaneous analysis of 16 sulfonamides (SAs) and five of their acetylated metabolites in groundwater. The evaluation of the degree of SA pollution in groundwater was made through the analysis of a total of 39 samples taken in seven groundwater bodies of Catalonia (Spain). Recovery values obtained ranged from 34.3% (N ⁴-acetylsulfadiazine) to 134.4% (sulfabenzamide). The method limits of detection for all the analytes were 0.09-11 ng L⁻¹. Sulfamethoxazole was the SA detected more frequently (56.4% of the samples), with an average concentration of 2.3 ng L⁻¹, followed by sulfadimethoxine, present in 54% of the samples with an average concentration of 0.2 ng L⁻¹. It should be highlighted that the acetylated metabolites were ubiquitous in the different samples, with frequencies of detection up to 36% and maximum concentrations of 18 ng L⁻¹ (N ⁴-acetylsulfamerazine).