Perfluoroalkanes (PFAs), a subclass of per- and polyfluoroalkyl substances (PFASs), are persistent environmental contaminants of growing global concern. The combination of high carbon–fluorine (C–F) bond stability and the absence of ionizable groups makes the direct detection of PFAs highly challenging, typically requiring complex sample preparation. Herein, we report a novel online ambient mass spectrometry (MS) approach for the rapid and sensitive analysis of PFAs without any sample pretreatment. This approach utilizes a corona discharge source to generate reactive water radical anions/cations (H 2 O –• /H 2 O +• ) in situ, which efficiently activate the inert C–F bond via a hydroxylation pathway, converting PFAs into readily detectable hydroxylated derivatives. The approach was demonstrated for perfluorooctane, perfluorohexane, and perfluoroheptane, achieving direct, real-time analysis, with limits of detection (LODs) ranging from 0.28 to 0.30 ng/L. The reaction mechanism and products were characterized using high-resolution MS, tandem MS, isotope labeling, and theoretical calculations. This H 2 O –• /H 2 O +• -induced strategy provides an efficient and powerful tool for the sensitive screening of PFAs in environmental samples.
Liu et al. (Fri,) studied this question.