Megumi Shimizu¹, Kendra Adams¹, Holly Lee¹, Simon Roberts¹, Sam Lodge², Cora Young³, Trevor VandenBoer³, RenXi Ye³ 

¹ Sciex, ² Phenomenex, ³ York University, Chemistry Department 

Ultrashort-chain perfluoroalkyl acids (PFAAs) (<4 carbons) have historically been overlooked due to their presumed low toxicity and bioaccumulation potential, as well as their relative analytical challenges due to poor retention on traditional reverse-phase LC columns and high background levels. However, studies have reported their global distribution in a variety of environmental matrices, frequently at levels higher than longer-chain PFAS. In this study, an LC-MS/MS method is developed based on mixed-mode chromatography which enables simultaneous analysis of ultrashort, short and long-chain (C1–C14) PFAAs at sub-to-low ng/L concentrations in different water matrices. Tap water, surface water and rainwater were collected from different regions in Ontario, Canada. Each water sample was diluted with methanol/water and spiked with internal standards for LC-MS/MS analysis. Sample extracts were chromatographically separated using a mixed-mode column that provided both C18- and ionic-based retention. Extensive chromatographic method development ensured good analyte retention from the void volume with TFA eluting first at ~5 minutes. Excellent quantitative performance was demonstrated based on the calibration linearity (r2 >0.99), accuracy and precision of solvent standards LOQs. The mass spectrometer sensitivity enabled a simple dilution approach at LOQs ranging from 0.1 to 10 ng/L for most of the target analytes. However, both TFA and PFBA required a higher LOQ of 50 ng/L to compensate for their background contamination. Tap water spikes prepared at varying concentrations demonstrated excellent recoveries (±30% of the nominal spiked value) and precision (<20%). Application of the method to drinking water, lake water and rainwater revealed the detection of some ultrashort-, short- and long chain PFAAs.