Determination of Perfluorooctane Sulfonyl Fluoride and Perfluorohexane Sulfonyl Fluoride in Soil by Chemical Derivatization and Liquid Chromatography–Tandem Mass Spectrometry

Perfluorooctane sulfonyl fluoride (PFOSF) and perfluorohexane sulfonyl fluoride (PFHxSF) were listed as persistent organic pollutants by the Stockholm Convention in 2009 and 2022, respectively. To date, their concentrations in environmental samples have not been reported due to the lack of sensitive methods. Herein, a novel chemical derivatization was developed for quantitative analysis of trace PFOSF and PFHxSF in soil by derivatizing them to the corresponding perfluoroalkane sulfinic acids. The method showed good linearity in the range from 25 to 500 ng L–1 with correlation coefficients (R2) better than 0.99. The detection limit of PFOSF in soil was 0.066 ng g–1 with recoveries in the range of 96–111%. Meanwhile, the detection limit of PFHxSF was 0.072 ng g–1 with recoveries in the range of 72–89%. Simultaneously, perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS) were also detected accurately without being affected by the derivative reaction. By applying this method in an abandoned fluorochemical manufacturing facility, PFOSF and PFHxSF were successfully detected at concentrations ranging from 2.7 to 357 ng g–1 and 0.23 to 26 ng g–1 dry weight, respectively. It is very interesting that 2 years after factory relocation, there still exists high concentrations of PFOSF and PFHxSF, which is of concern.