Large-Volume Dilute-and-Shoot Analysis of PFAS in Drinking Water Using the Altura PFAS Column

Significance of the topic

Per- and polyfluoroalkyl substances (PFAS) are persistent, mobile synthetic chemicals of significant public-health concern. Regulatory attention on PFAS in drinking water is rising globally and requires analytical methods that combine trace-level sensitivity with practical throughput for routine monitoring. Large-volume dilute-and-shoot strategies that avoid labor-intensive solid-phase extraction (SPE) can shorten turnaround times while meeting stringent detection requirements when paired with suitable chromatography and sensitive tandem mass spectrometry.

Objectives and study overview

This application note evaluates a large-volume dilute-and-shoot LC–MS/MS workflow for nine legacy PFAS (C4–C10), demonstrating direct injection of 200 µL water samples diluted in methanol on an Agilent Altura Poroshell 120 PFAS column. The main goals were to (1) extend dilute-and-shoot sensitivity to sub-ng/L levels relevant for drinking water, (2) maintain chromatographic performance and robustness at high injection volumes, and (3) assess method accuracy, precision, and method detection limits (MDLs) in several real water matrices.

Methodology

• Analytes: PFBS, HFPO-DA (GenX), PFHpA, PFHxA, PFHxS, PFOA, PFOS, PFNA, PFDA.
• Sample preparation: 3 mL water sample spiked with native PFAS (1 and 10 ng/L test levels), amended with 10 ng/L isotopically labeled PFAS mix, diluted with 3 mL methanol (final 1:1, water:methanol). Additives: ascorbic acid (10 µg/mL) to dechlorinate and 10 µL acetic acid to improve peak shape. Vortex 2 min and filter through 0.2 µm RC filter. Final vial volume 6 mL; 200 µL injected.
• Calibration: in-vial range 0.25–25 ng/L (equivalent to 0.5–50 ng/L in samples) using 1/x weighted linear regression. Reported linearity R2 > 0.99 for all targets.

Used Instrumentation

• LC: Agilent 1290 Infinity II (high-speed pump, multisampler with extended multidraw capillary for large-volume injection, multicolumn thermostat).
• Column: Agilent Altura Poroshell 120 PFAS, 2.1 × 50 mm, 2.7 µm; PFAS delay column (4.6 × 30 mm) used.
• MS: Agilent 6495D triple quadrupole LC/MS with Agilent Jet Stream source.
• Key LC conditions: column temp 50 °C, flow 0.400 mL/min, mobile phases A = 2 mM ammonium acetate in H2O, B = 2 mM ammonium acetate in MeOH, injection volume 200 µL, total run ~12 min.
• Representative MS source settings: gas temp 200 °C, nebulizer 33 psi, sheath gas temp 310 °C, capillary voltage ~2100 V. MRM transitions were taken from Agilent PFAS MRM database and optimized for labeled homologues.

Main results and discussion

• Chromatography: All nine PFAS were separated with Gaussian peak shape at 200 µL injection, demonstrating the Altura PFAS column tolerates large-volume methanol/water injections without notable tailing or retention loss.
• Linearity and calibration: Calibration in-vial 0.25–25 ng/L (0.5–50 ng/L in sample) produced R2 > 0.99 and accuracies between ~95–115% across calibration levels.
• Repeatability and column stability: Seven-replicate tests at 0.25 and 2 ng/L showed accuracy ranges ~82–108% (0.25 ng/L) and ~87–106% (2 ng/L) with abundance %RSD < 11–12% and retention-time %RSD < 0.1, indicating robust retention stability under repeated large-volume injections.
• Method detection limits (MDLs): MDLs calculated from seven low-level spikes (with blanks considered) ranged from 0.37 to 1.15 ng/L across the panel (compound-dependent). These MDLs enable quantitation below many regulatory thresholds and substantially improve the low-end sensitivity relative to typical small-volume dilute-and-shoot protocols.
• Matrix performance: Matrix spike experiments in reagent water, municipal tap water and household filtration samples (prefilter, postfilter, reverse osmosis) showed recoveries generally within 75–99% and inter-replicate %RSD < 7% for matrix spikes (1 and 10 ng/L levels). Minimal matrix interference was observed after subtraction of isotopically labeled internal standards.

Benefits and practical applications of the method

• Throughput: Eliminating SPE reduces hands-on sample preparation and enables faster processing of routine drinking water samples.
• Sensitivity: Large-volume (200 µL) injection combined with a high-sensitivity triple quadrupole achieves sub-ng/L MDLs suitable for current and anticipated regulatory limits.
• Robustness: The Altura PFAS column maintained peak shape and retention stability under repeated large-volume injections, supporting reliable long-term monitoring programs.
• Operational simplicity: The protocol uses simple additives (ascorbic acid, small acetic acid addition) and filtration, avoiding complex extraction workflows while maintaining quantitative performance with isotope dilution.

Limitations and considerations

• Target scope: The workflow targets selected legacy C4–C10 PFAS and GenX (HFPO-DA). Broader PFAS screening (short-chain fluorotelomer precursors, polymers, ultratrace contaminants) may require complementary methods or non-target approaches.
• PFAS background and contamination control: Laboratories must use PFAS-free consumables, delay columns, and careful blanks management to avoid background contamination from solvents, tubing, or vials.
• Dependence on labeled standards: Accurate quantitation and matrix compensation rely on appropriate isotopically labeled surrogates for each analyte class.

Future trends and potential applications

• Method expansion: Extension to a wider range of PFAS (including emerging short-chain and polymeric species) and incorporation of non-target screening workflows will broaden environmental surveillance.
• Automation and throughput: Integration with automated sample handling and large-batch autosampler configurations could further increase laboratory throughput for regulatory monitoring programs.
• Lower MDLs and hybrid workflows: Combining controlled preconcentration or trap-based approaches with large-volume injection and next-generation MS could push MDLs lower while retaining operational efficiency.
• Regulatory harmonization: As MCL values and monitoring requirements evolve, validated rapid methods like this can be standardized across labs to streamline compliance testing.

Conclusion

This application demonstrates that large-volume (200 µL) dilute-and-shoot injection on an Altura Poroshell PFAS column, coupled to a high-sensitivity triple quadrupole LC/MS, provides a practical, high-throughput approach for quantifying selected C4–C10 PFAS in drinking water at sub-ng/L levels. The method yields strong linearity (R2 > 0.99), MDLs of ~0.37–1.15 ng/L, good recoveries (typically 75–108% in matrices tested), and reproducible performance with low RT variability, making it attractive for routine monitoring where reduced sample preparation time and robust trace sensitivity are required.

Reference

1. United States Environmental Protection Agency. Method 8327. SW-846 Test Method 8327: Per-and polyfluoroalkyl Substances (PFAS) by Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS). July 2021.
2. ASTM International. ASTM D8421‑22: Standard Test Method for Determination of Per‑ and Polyfluoroalkyl Substances (PFAS) in Aqueous Matrices by Co‑solvation Followed by Liquid Chromatography Tandem Mass Spectrometry (LC/MS/MS). Last updated June 2024.
3. Fu, R.; Yao, W.; Wang, Z.; Huang, I. Simultaneous C1–C18 PFAS Analysis in Drinking Water by Large-Volume Direct Injection Using an Altura Poroshell 120 PFAS Column. Agilent Technologies application note, publication number 5994-8895EN, 2026.
4. U.S. Environmental Protection Agency. Definition and procedure for the determination of the method detection limit (MDL), Revision 2 (EPA 821‑R‑16‑006). 2016.