Determination of Polyfluoroalkyl Substances (PFAS) in Food Products Agustin Pierri, PhD ASMS 2017 Indianapolis, IN
Background
Polyfluoroalkyl Substances (PFASs) Aliphatic backbone from C 4 on up Typically per-fluorinated Acid functional group Unique environmental chemistry Persistent Lipophilic Bioaccumulative
Polyfluoroalkyl Substances (PFASs) Uses? Repellents Performance chemicals Consumer and industrial goods
Polyfluoroalkyl Substances (PFASs) Routes of exposure Direct contact with food products Environmental exposure
Target compounds 6:2 FTS 8:2 FTS EtFOSA MeFOSA FOSA EtFOSE MeFOSE PFBA PFBS PFDA PFDS PFHpA PFHpS PFHxA PFHxS PFNA PFOA PFOS PFPeA PFDoA PFTeDA PFTrDA PFUdA Carboxylic acids Sulfonic acids Sulfonamides Sulfonamido-ethanols
Sample prep
Sample prep approach SPE: Only suitable for water samples Weak anion exchange offline SPE QuEChERS: Suitable for non-liquid samples
QuEChERS Screening: C18 d-spe C18 d-spe + hexanes PSA/GCB d-spe C18/GCB d-spe C18/GCB d-spe + hexanes EMR-L
EMR-Lipids procedure Weigh 2.0 grams homogenized sample into 50 ml tube Add 10 ml MeCN, vortex 3 minutes Add 2 g of EMR-L + 10 ml H 2 O Vortex 1 minute, centrifuge 5 minutes Transfer 5 ml aliquot to tube with 2.5 g NaCl/MgSO 4 Transfer 200 µl to conical vial for analysis Based on: Anumol, T., Lehotay, S.J., Stevens, J. et al. Anal Bioanal Chem (2017) 409: 2639
Analysis: LC/MS
PFAS by LC/MS Unique analytical challenges Low levels Relative polarities Isomers Contamination
Sensitivity 1290 LC, 6460 QQQ Choosing the right mobile phase modifier
Mobile phase modifiers for ESI Negative mode Ammonium salts Ammonium acetate Ammonium formate Ammonium fluoride the secret sauce (usually)
Mobile phase vs PFBA Ammonium acetate Acetic acid Ammonium formate Ammonium fluoride Most polar:
Chromatographic conditions Column: Zorbax RRHD Eclipse Plus C18 50 x 2.1 1.8 μm Injection volume: 2 μl Mobile phase: A: Water with 0.05% acetic acid B: Acetonitrile with 0.05% acetic acid Flow rate: 0.700 ml/min Time %B 0.0 5 0.5 5 1.0 40 7.0 90 7.2 100 9.5 100
Mid level chromatogram (1 ppb)
Low level (0.1 ppb) Low levels:
Solvent blank Instrument contamination:
Branched vs. linear sulfonates PFHxS PFOS Isobars:
Dynamic range Calibrates up to 0.1 ppb 1000 ppb
Method performance
Extracts Blank Milk Egg Fish Butter
PFBA PFPeA PFBS PFHxA PFHpA PFHxS 6:2 FTS PFOA PFHpS PFOS PFNA FOSA Me-FOSE 8:2 FTS Me-FOSA PFDA Et-FOSE Et-FOSA PFDS PFUdA PFDoA PFTrDA PFTeDA Absolute recoveries, milk 160 Milk, ESTD 140 120 100 80 60 40 20 0
PFBA PFPeA PFBS PFHxA PFHpA PFHxS 6:2 FTS PFOA PFHpS PFOS PFNA FOSA Me-FOSE 8:2 FTS Me-FOSA PFDA Et-FOSE Et-FOSA PFDS PFUdA PFDoA PFTrDA PFTeDA Absolute recoveries, egg 160 Egg, ESTD 140 120 100 80 60 40 20 0
PFBA PFPeA PFBS PFHxA PFHpA PFHxS 6:2 FTS PFOA PFHpS PFOS PFNA FOSA Me-FOSE 8:2 FTS Me-FOSA PFDA Et-FOSE Et-FOSA PFDS PFUdA PFDoA PFTrDA PFTeDA Absolute recoveries, butter 160 Butter, ESTD 140 120 100 80 60 40 20 0
PFBA PFPeA PFBS PFHxA PFHpA PFHxS 6:2 FTS PFOA PFHpS PFOS PFNA FOSA Me-FOSE 8:2 FTS Me-FOSA PFDA Et-FOSE Et-FOSA PFDS PFUdA PFDoA PFTrDA PFTeDA Absolute recoveries 160 Fish, ESTD 140 120 100 80 60 40 20 0
PFBA PFPeA PFBS PFHxA PFHpA PFHxS 6:2 FTS PFOA PFHpS PFOS PFNA FOSA Me-FOSE 8:2 FTS Me-FOSA PFDA Et-FOSE Et-FOSA PFDS PFUdA PFDoA PFTrDA PFTeDA Isotopic dilution corrected recoveries, milk 160 Milk, ESTD ISTD 140 120 100 80 60 40 20 0
PFBA PFPeA PFBS PFHxA PFHpA PFHxS 6:2 FTS PFOA PFHpS PFOS PFNA FOSA Me-FOSE 8:2 FTS Me-FOSA PFDA Et-FOSE Et-FOSA PFDS PFUdA PFDoA PFTrDA PFTeDA Isotopic dilution corrected recoveries, egg 160 Egg, ESTD ISTD 140 120 100 80 60 40 20 0
PFBA PFPeA PFBS PFHxA PFHpA PFHxS 6:2 FTS PFOA PFHpS PFOS PFNA FOSA Me-FOSE 8:2 FTS Me-FOSA PFDA Et-FOSE Et-FOSA PFDS PFUdA PFDoA PFTrDA PFTeDA Isotopic dilution corrected recoveries 160 Butter, ESTD ISTD 140 120 100 80 60 40 20 0
PFBA PFPeA PFBS PFHxA PFHpA PFHxS 6:2 FTS PFOA PFHpS PFOS PFNA FOSA Me-FOSE 8:2 FTS Me-FOSA PFDA Et-FOSE Et-FOSA PFDS PFUdA PFDoA PFTrDA PFTeDA Isotopic dilution corrected recoveries 160 Fish, ESTD ISTD 140 120 100 80 60 40 20 0
PFBA PFPeA PFBS PFHxA PFHpA PFHxS 6:2 FTS PFOA PFHpS PFOS PFNA FOSA Me-FOSE 8:2 FTS Me-FOSA PFDA Et-FOSE Et-FOSA PFDS PFUdA PFDoA PFTrDA PFTeDA Robust and versatile method for PFAS in food Challenges unique to PFAS Trace levels MRL at 0.5 ng/g Instrument contamination Resolution Handle complicated matrix Butter, ISTD 160 140 120 100 80 60 40 20 0
Questions? Agustin Pierri agustin.pierri@wecklabs.com 626-336-2139 Weck Laboratories, Inc. Industry, CA 91745