High-Throughput Ultra-Short-Chain PFAS Analysis in Drinking Water using LC-MS/MS with Automated Sample Preparation

Importance of the topic

Per- and polyfluoroalkyl substances (PFAS), including ultra-short- and short-chain homologues, are increasingly monitored in drinking water because of their environmental persistence, mobility, and potential health impacts. Analytical challenges for these compounds include very high polarity, low molecular weight, weak chromatographic retention and frequent contribution from laboratory or solvent background. Developing a high-throughput, robust LC–MS/MS workflow with automated sample preparation improves routine monitoring capacity, supports regulatory compliance, and reduces turnaround time for water-quality laboratories.

Objectives and study overview

This study evaluated a targeted, high-throughput LC–MS/MS workflow for nine ultra-short- and short-chain PFAS in seven drinking-water matrices. Goals were to assess method linearity, limits of quantification (LOQs), calibration performance, matrix spike recovery, precision (including continuing calibration verification, CCV), and the impact of native matrix background on low-level quantification. The workflow used an automated ePrep sample-preparation platform coupled to a Shimadzu LCMS-8065XE triple-quadrupole system with an 8-minute total cycle time.

Methodology

Key experimental design elements:

• Analytes: nine target PFAS — TFA, TFMS, PFPrA, PFMOAA, PFEtS, PFBA, PFPrS, TFSI, and PFBS.
• Calibration: nine-point calibration (10–2500 ng/L for most analytes; PFMOAA: 50–2500 ng/L).
• Sample preparation: automated ePrep platform using acidified 50:50 PFAS-grade water/methanol and PFAS-grade water to prepare calibrants and samples.
• Chromatography: polar-embedded IBD stationary phase with an inline delay column to enhance retention of very polar analytes and reduce background interferences.
• MS detection: triple-quadrupole MRM acquisition on Shimadzu LCMS-8065XE with a 10 µL injection volume and an ~8-minute run per sample.
• Evaluation: seven household drinking-water sources analyzed unspiked and spiked at multiple concentrations (10, 100, 500, 1000 ng/L) in replicate to quantify recovery, precision, and method robustness.

Used instrumentation

Instruments and consumables explicitly used and described in the study:

• Shimadzu LCMS-8065XE triple-quadrupole mass spectrometer.
• High-performance liquid chromatography system equipped with a polar-embedded IBD column and a delay column to improve retention and lower background.
• ePrep automated sample-preparation workstation configured with PFAS-free accessories.
• PFAS-grade solvents and MilliporeSigma PFAS-grade water for calibrants and method blanks.

Main results and discussion

Calibration and sensitivity:

• All analytes except PFMOAA were validated to a practical LOQ of 10 ng/L; PFMOAA was validated at 50 ng/L.
• Linearity was excellent across the calibrated ranges with R2 values >0.99 for all targets.
• Continuing calibration verification (CCV) demonstrated system stability with %RSD (n=79 injections) ranging from ~9% to 28%; most compounds were below 16% RSD, while PFMOAA showed the highest variability (28% RSD).

Precision and recovery:

• Matrix spike recoveries were generally within the 70–130% acceptance criteria for spikes at 100–1000 ng/L across the seven drinking-water matrices, supporting method robustness for routine monitoring levels.
• At 10 ng/L, recoveries displayed larger variance and were more strongly influenced by native/background contributions; results at this low level should be interpreted with caution, especially where native concentrations are non-negligible.
• PFMOAA consistently showed lower recoveries and higher variability across matrices, indicating potential ionization or extraction inefficiencies and the need for targeted optimization for that analyte.

Background contamination and matrix effects:

• Trifluoroacetic acid (TFA) was present as a measurable background in solvent blanks and was detected in all seven unspiked household water samples at concentrations exceeding 1000 ng/L, highlighting a pervasive environmental or laboratory source for this compound and the importance of blank screening and solvent selection.
• PFPrA and several other targets showed low or no blank response; however, one drinking-water matrix had elevated native PFAS that affected spike-recovery calculations, underscoring the need for matrix-specific background assessment prior to method validation or reporting.

Benefits and practical application of the method

The presented workflow offers several practical advantages:

• High throughput: ~8-minute cycle time per sample enables rapid turnaround for large sample batches in monitoring programs.
• Automation: ePrep sample-preparation reduces manual handling, improves reproducibility and minimizes operator time.
• Sensitivity and dynamic range: validated LOQs (10–50 ng/L) and wide calibration up to 2500 ng/L accommodate both low-level surveillance and detection of elevated contamination events.
• Robustness: consistent CCV results and acceptable recoveries at relevant spike levels (100–1000 ng/L) make the method suitable for routine drinking-water testing with appropriate QA/QC.

Future trends and possibilities for use

Opportunities and directions to further improve PFAS monitoring workflows include:

• Improved controls for ubiquitous background analytes like TFA, including further solvent purification, lab contamination audits, and tailored blank-correction strategies.
• Method optimization for challenging analytes (e.g., PFMOAA) to enhance extraction efficiency and reduce variability, potentially via alternative sample-prep chemistries or internal-standard strategies.
• Extension of automated workflows to include isotopically labeled internal standards and on-instrument flagging of matrix effects to improve low-level quantitation confidence.
• Application of the rapid LC–MS/MS approach in large-scale regulatory monitoring, emergency response for contamination events, and longitudinal studies assessing source trends.

Conclusion

This study demonstrates a rapid, automated LC–MS/MS workflow capable of quantifying nine ultra-short- and short-chain PFAS in drinking water with acceptable linearity, precision and recovery for routine concentration ranges (100–1000 ng/L). Practical LOQs of 10 ng/L (most analytes) and 50 ng/L (PFMOAA) were achieved, while widespread TFA background and variability at very low spike levels highlight the need for vigilant blank control and matrix-specific assessment. PFMOAA was identified as the primary target requiring further optimization.

References

1. U.S. Environmental Protection Agency. Method 533: Determination of Per- and Polyfluoroalkyl Substances in Drinking Water by Isotope Dilution Anion Exchange Solid Phase Extraction and Liquid Chromatography/Tandem Mass Spectrometry; EPA 815-B-19-020; U.S. EPA: Washington, DC, 2019.
2. ASTM International. ASTM D8421-22: Standard Test Method for Determination of Per- and Polyfluoroalkyl Substances in Aqueous Matrices by Co-solvation Followed by Liquid Chromatography Tandem Mass Spectrometry (LC/MS/MS); ASTM International: West Conshohocken, PA, 2022.
3. U.S. Environmental Protection Agency. Sampling for PFAS under the National Primary Drinking Water Regulation; U.S. EPA: Washington, DC, 2025.