Acrodisc filter recovery optimization for PFAS analytes and surrogates. The isotope mass labeled 13C2–4:2 FTS, 13C4-PFOA, 13C4-PFOS and 13C5-PFNA, are surrogates and others are target analytes. Trial 1, Acrodisc filter conditioned with 1.0 mL nanopure water; Trial 2, Acrodisc filter conditioned with 5.0 mL acetonitrile following 5.0 mL methanol; Trial 3, Acrodisc filter conditioned with 5.0 mL acetonitrile following 5.0 mL methanol and after loading the sample filter was rinsed with 1.0 mL methanol; CCV, continuous calibration verification or laboratory control sample used to calibration check through the analysis.