Determination of Analytical Interferences for 4:2 Fluorotelomer Sulfonic Acid in Multiple Agricultural Matrices

During analysis of corn snaplage, fiddleheads, and hay for per- and polyfluoroalkyl substances (PFAS) using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) triple quadrupole method, a series of interferents were observed for 4:2 fluorotelomer sulfonic acid (4:2 FTS, m/z 326.9743). Liquid chromatography high-resolution mass spectrometry (LC-HRMS) and MS/MS were used to identify these interferents as corchorifatty acid F and other complex lipids capable of generating m/z 327.2177. Approaches to differentiate 4:2 FTS from these interferents included HRMS, scheduling alternate transitions in triple quadrupole methods to monitor for the presence of these interferents, and altering the chromatography conditions (e.g., C-18 vs C-18 PFP column). Importantly, reporting these findings and adding these interferents to the PFAS interference list (PIL) for 4:2 FTS raise awareness for the possibility of matrix interferences in these agricultural products and reduce future false positive and/or over-reporting of PFAS in complex samples.