Analysis of per- and polyfluorinated alkyl substances in sub-sampled water matrices with online solid phase extraction/isotope dilution tandem mass spectrometry.

Sorption of PFASs onto surfaces of laboratory materials has been frequently reported. Due to the often complex and poorly understood nature of such sorption, workarounds have often included use of whole samples only, accompanied by sample vessel rinsing to desorb active surfaces. The resulting methods tend to require considerable sample preparation times and preclude typical activities such as aliquoting and dilution of water samples prior to extraction. This manuscript reports an approach for PFAS analysis which uses subsampling of water matrices from vessels including centrifuge tubes and autosampler vials, through the optimized use of solvent to reduce PFAS retention on subsampling vessels. Online solid phase extraction (SPE) using a weak anion exchange resin is then used to concentrate sample aliquots to improve sensitivity and allow for removal of matrix interferences. With the technique of ultra performance liquid chromatography (UPLC) coupled to isotope dilution tandem mass spectrometry, statistically based quantitation limits ranged from sub ng/L to single digit ng/L for carboxylate, sulfonate, and sulfonamide PFASs analytes from C4 to C12. Linear calibration ranges were from 0.25 to 4000 ng/L. Matrix effects relevant for drinking water treatment studies, such as cations, organic carbon, and competing PFAS compounds, were evaluated and found to not impact method performance within QC criteria consistent with study data quality objectives.