Determination of perfluorobutane sulfonyl fluoride in environmental water and soil using a novel quaternary ammonium derivatization LC-MS/MS method.

Although current derivatization methods have enabled the detection of perfluorooctane sulfonyl fluoride (PFOSF) and perfluorohexane sulfonyl fluoride (PFHxSF), the analysis of their short-chain substitute, perfluorobutane sulfonyl fluoride (PFBSF), remains challenging despite its increasing production. This study developed a novel quaternary ammonium derivatization reagent and established a highly sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the trace quantification of PFBSF in water and soil, while enabling the simultaneous determination of PFHxSF and PFOSF. Method validation demonstrated exceptional sensitivity, with method detection limits (MDLs) for PFBSF reaching 0.84 ng L-1 in water and 0.022 ng g-1 in soil. For PFHxSF and PFOSF, the MDLs ranged from 0.93 to 0.98 ng L-1 in water and 0.027-0.030 ng g-1 in soil. The method exhibited excellent linearity (R2 > 0.99 over 5-100 ng L-1), stable recoveries (71%-116%), and satisfactory specificity and stability. This method was successfully applied to environmental samples collected near an abandoned fluorochemical plant in Wuhan. PFBSF, PFHxSF, and PFOSF were widely detected at respective concentrations of 12.12-147.94 ng L-1, 7.75-231.88 ng L-1, and 8.33-26.81 ng L-1 in water, and 0.71-4.19 ng g-1, 0.37-12.81 ng g-1, and 0.29-2.40 ng g-1 in soil. The concurrent detection of high perfluoroalkane sulfonic acid (PFSA) concentrations confirmed the plant as a major point source for both compound classes. Furthermore, temporal monitoring from 2023 to 2025 revealed that regional perfluoroalkyl sulfonyl fluorides (PFASFs) contamination has decreased to a certain extent, whereas PFSA levels remain elevated, warranting continued regulatory attention.