Analysis of Perfluorooctanesulfonate Isomers and Other Perfluorinated Alkyl Acids in Serum by In-Port Arylation Gas Chromatography Negative Chemical Ionization–Mass Spectrometry

Perfluorooctanesulfonate (PFOS) is a common environmental pollutant and has been detected in various environmental media. Several major isomers have been identified, and their profiles provide important signatures from the source of contamination. Gas chromatography has a significant resolving power for the isomers. However, methods for derivatizing sulfonates for a sensitive analysis are limited. In this study, in-port derivatization with diaryl iodonium salts into aryl sulfonates was used. A technical mixture of PFOS was separated on gas chromatography to afford 11 isomers. In electron-capture negative ionization, the PFOS derivatives form specific fragmented anions (sulfinate anions). The derivatization was also applied to other per- or polyfluoroalkyl acids (PFASs; 13 perfluoroalkyl carboxylic acids and 10 sulfonates). Analysis of human serum samples was achieved with as little as 50 μL of sample and indicated the presence of PFOS isomers and PFASs. The detection limits of PFOS isomers were 0.02–0.09 ng mL^–1 with sufficient recoveries (85%–98%), and those for other PFASs ranged from 0.01–1 ng mL^–1 (recoveries, 80%–100%), which are suitable for the analysis of human serum samples.