Determination of 30 PFAS in Foods for Infants and Young Children (Baby Food) by Liquid Chromatography Triple Quadrupole Mass Spectrometry (LC-MS/MS)

Significance of the topic

Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative synthetic chemicals of high regulatory and public-health concern. Low parts-per-trillion concentrations in foodstuffs intended for infants and young children require analytical methods that are sensitive, selective, reproducible and compliant with regulatory performance criteria. This study demonstrates a validated workflow for simultaneous measurement of 30 PFAS in baby food matrices, addressing practical needs for rapid sample throughput, low limits of quantitation (LOQs), and robust quality control consistent with AOAC SMPR 2023.003.

Objectives and study overview

• Develop and validate a single-laboratory method to quantify 30 PFAS in infant baby food (pumpkin and sweet potato purees).
• Achieve sensitivity, accuracy, and precision consistent with AOAC SMPR 2023.003.
• Implement a fast, simple extraction (QuEChERS) combined with WAX cleanup and UHPLC–triple quadrupole MS/MS (Shimadzu Nexera + LCMS-8060NX).
• Use matrix-matched calibration and isotope-dilution quantification to minimize matrix bias and improve accuracy at low ng/g (ppb) levels.

Methodology

• Sample preparation: Multiple commercial jars of baby food were combined and homogenized. Ten-gram aliquots were spiked (triplicate) at four concentration levels and fortified with 16 isotopically labeled internal standards.
• Extraction: 10 mL acetonitrile was added to 10 g sample; samples were shaken, treated with a QuEChERS salt packet, cooled, and centrifuged. The acetonitrile layer was diluted fivefold with PFAS-free water and subjected to weak anion exchange (WAX) SPE. PFAS were eluted with basic methanol, concentrated to <1 mL and adjusted to 1 mL in a methanol–water mixture before injection.
• Chromatography: UHPLC separation (Shimadzu Nexera) achieved full separation of all target compounds within a nine-minute runtime. Chromatographic optimization included evaluation of multiple columns and gradients to resolve critical interferences and isomers.
• Mass spectrometry: Shimadzu LCMS-8060NX triple quadrupole operated with heated electrospray ionization in negative ion mode. MRM transitions were tuned and optimized; both quantifier and qualifier ions monitored per analyte to meet ion-ratio and retention-time criteria.
• Calibration and quantitation: Matrix-matched calibration standards (0.005–1.0 ng/g) underwent the same extraction and cleanup. Isotope-dilution calibration (linear model not forced through zero) provided best fit; calibration residuals were within ±25% for points across the curve.
• Validation design: Samples spiked at multiple levels (including the SMPR-required LOQs and up to 100×) were analyzed in triplicate. LOQs were set as the lowest spike level meeting accuracy, repeatability (RSD), ion-ratio, retention-time consistency and qualifier S/N criteria (S/N >3; some compounds required S/N >10).

Instrumentation

• UHPLC: Shimadzu Nexera series high-performance liquid chromatograph.
• Mass spectrometer: Shimadzu LCMS-8060NX triple quadrupole with enhanced ion-focus design and heated ESI (negative mode).
• Sample prep: QuEChERS extraction salts/packets, weak anion exchange (WAX) SPE cartridges, centrifugal concentrator for solvent reduction.
• Standards: 30 native PFAS standards and 16 isotopically labeled internal standards for isotope-dilution quantitation.

Main results and discussion

• Analyte scope: 30 PFAS covering perfluoroalkyl carboxylic acids (C4–C14), sulfonic acids (including PFOS and homologues), FOSA, chlorinated perfluoroalkyl sulfonic acids, HFPO-DA (GenX), DONA, and various fluorotelomer sulfonates (4:2–10:2 FTS).
• LOQs: Experimentally determined LOQs met SMPR requirements. Most long-chain PFAS achieved LOQs of 0.01 ppb; some short-chain species and a few sulfonates were at 0.1 or 0.01 ppb depending on signal and matrix behavior.
• Recovery and precision: Recoveries across spikes were generally within approximately 80–117% depending on compound and level, with repeatability (RSD) typically low (often <5% at mid-to-high spikes, higher variability at the lowest levels but still within acceptance limits).
• Calibration performance: Six-point matrix-matched isotope-dilution calibration (0.005–1.0 ng/g) produced accurate quantitation with residuals within ±25% and good linearity for critical analytes PFOA, PFHxS, PFNA and PFOS. Branched and linear isomers for PFHxS and PFOS were integrated together for quantitation; chromatography provided baseline separation between isomers and a two-minute offset between PFOS and cholic-acid interferences.
• Optimization effort: Extensive method development (1984 instrument-setting permutations and six column/gradient combinations) improved peak shape, chromatographic resolution and sensitivity, particularly for PFOA, PFHxS, PFNA and PFOS.
• Quality criteria: LOQs were only accepted when the qualifier ion met S/N and ion-ratio constraints (ion ratio ±30%) and retention time matched the standard, ensuring selectivity at low ng/g levels.

Benefits and practical applications

• Regulatory compliance: Method meets AOAC SMPR 2023.003 single-laboratory criteria, making it suitable for regulatory testing and surveillance of baby foods.
• Throughput and practicality: QuEChERS-based extraction and short UHPLC runtime (9 minutes) enable relatively high sample throughput with simplified consumables and workflows suitable for routine labs.
• Sensitivity and robustness: Isotope-dilution calibration and WAX cleanup produce low LOQs and reliable recoveries across diverse PFAS chemistries.
• Applicability: Workflow can be adapted to other food matrices with appropriate matrix-matched calibration and procedural blanks; baseline isomer resolution supports more detailed isomer-specific assessments where required.

Future trends and opportunities

• Broader panels and non-target screening: Expansion of target lists and incorporation of high-resolution mass spectrometry (HRMS) for unknown PFAS and transformation products will improve comprehensive exposure assessment.
• Automated and miniaturized sample preparation: Robotic QuEChERS workflows and reduced solvent consumption will increase throughput and reduce laboratory footprint and contamination risk.
• Standardization and interlaboratory studies: Wider adoption of harmonized protocols and multi-laboratory validations will strengthen comparability across monitoring programs.
• Isomer-specific quantitation: Improved chromatographic and MS approaches can enable routine differentiation and quantitation of branched vs linear isomers for source attribution and toxicological interpretation.
• Mitigation of contamination: Continued emphasis on PFAS-free consumables, rigorous blank strategy and laboratory contamination control will remain critical for low-ng/g analyses.

Conclusion

This work presents a validated, high-performance LC–MS/MS workflow for quantifying 30 PFAS in baby food matrices that satisfies AOAC SMPR 2023.003 performance criteria. The combination of rapid QuEChERS extraction, WAX SPE cleanup, matrix-matched isotope-dilution calibration, and optimized UHPLC–MS/MS (Shimadzu Nexera + LCMS-8060NX) delivered low LOQs, reliable recoveries and precision within acceptance limits. The method balances sensitivity, selectivity and throughput and is directly applicable to regulatory testing and routine monitoring of infant food products.

References

• AOAC SMPR 2023.003