Abstract: We looked at how well a direct injection UHPLC-MS/MS method could analyze several perfluoroalkyl acids (PFAAs) in all sorts of water. The method’s simple: just inject 100 µL of centrifuged water, no other steps needed. We got really good detection limits, from 0.014-0.44 µg L-1, and excellent precision, with RSD% values between 1.8-4.4% for within-day tests and 2.7-5.7% for between-day tests. The whole analysis takes just 20 minutes per sample. We ran a lot of samples: 8 drinking waters (DW), 12 ground waters (GW), 13 surface waters (SW), 8 influents and 11 effluents from wastewater treatment plants (WWTPIN and WWTPOUT). We calculated the matrix effect (ME) for each, and most showed a small effect, less than 20%. Occasionally, we saw a bigger effect, over 50%, but only for perfluorooctanesulphonic and perfluorodecanoic acids. Linear discriminant analysis showed that where the sample came from – like drinking water, ground water, surface water, or wastewater plant influent and effluent – really influenced the matrix effect. We also used partial least square regression (PLS) and leave-one-out cross-validation to try and figure out why signals were suppressed or enhanced. We checked this against water parameters like conductivity, hardness, chemical oxygen demand, and background chromatographic area. The PLS approach gave us a rough idea, but its prediction power wasn’t super strong. Still, for most analytes in most samples, the values helped us tell if the matrix effect was higher or lower than 20%. We quantified PFAAs in all those water samples using the standard addition method. It turns out they’re mostly in wastewater treatment plant influents and effluents, sometimes at concentrations as high as one hundred µg L-1.

Source: Water Feed