Preparation of superhydrophobic fluorine-containing magnetic particles and their application in the determination of trace perfluorocarboxylic acids in water

Background The monitoring of perfluorocarboxylic acids (PFCAs), a new class of persistent pollutants, has attracted widespread public concern. However, achieving highly selective enrichment of trace PFCAs in environmental samples remains a challenge for analysts. Results In this work, we have successfully prepared a new superhydrophobic fluorine-containing magnetic particles, Fe 3 O 4 @SiO 2 @CF&TMS, by modifying the surface of Fe 3 O 4 particles. By sealing their residual silanol groups, this material exhibited exceptional hydrophobicity, enabling efficient extraction of PFCAs. Using magnetic solid phase extraction (MSPE) with the prepared magnetic particles, a recovery rate of above 95.5% was achieved for PFCAs from real water within 5 min. Extraction recovery rates remained at 85%-112% for PFCAs in water in 5 consecutive extractions. Based on the MSPE method with this material, in combination with methylation with trimethylsilane diazomethane, and GC-MS analysis, a selective analytical method was developed for determining of 9 PFCAs in various real water samples, including surface water and sewage plant water. This method demonstrated good reproducibility, sensitivity, and anti-interference capability, with the intra-day relative standard deviation (RSD, n = 3) in the range of 0.15-4.87% and a limit of quantification of 0.020 ng/mL, even in the presence of humic acid (5 μg/mL). Experimental results revealed that the detected content of medium- and long-chain PFCAs in various surface water samples ranged from