Streamlined Measurement of Ultra-Short Chain PFAS in Landfill Groundwater via Altura Column Chemistry and LC-MS/MS

Importance of the Topic

The detection of ultra-short chain per- and polyfluoroalkyl substances (PFAS; C2–C3) in environmental waters presents analytical challenges because these analytes are poorly retained on conventional reversed-phase columns, occur at low ng/L concentrations, and coexist with high-ionic-strength matrices. Reliable, sensitive, and streamlined workflows for direct-injection LC–MS/MS analysis of these compounds enable faster monitoring of groundwater and landfill leachate, reduce sample preparation complexity, and facilitate comparison to regulatory or reference methods such as EPA 1633A.

Objectives and Study Overview

This work evaluated a direct-injection LC–MS/MS workflow for nine ultra-short chain PFAS in high-ionic-strength synthetic water and real landfill groundwater. Key aims were to: determine method detection limits (MDLs), assess retention-time stability across matrices with different conductivities, evaluate matrix-spike recoveries and precision, and compare direct-injection PFBA quantitation to results obtained by a collaborator using EPA Method 1633A (solid-phase extraction). The study focused on practical performance when using Altura PFAS column chemistry paired with an Agilent LC–MS/MS platform.

Methodology

The workflow used direct injection of minimally prepared groundwater samples. Sample handling was simple: 600 µL aliquots were centrifuged and supernatant transferred to vials with added isotopically labeled internal standards. Calibration standards and blanks were prepared in reverse‑osmosis water; the calibration range spanned 0.005–2 ng/mL (adjusted for TFA due to background presence). A laboratory synthetic water (high salt matrix) was formulated to challenge column performance and assess matrix effects. Field samples from seven landfill monitoring wells, previously analyzed by EPA 1633A, were included for method comparison.

Key analytical considerations and observations:

• Ambient TFA background in the laboratory required raising TFA spike levels and adjusting MDL estimation to account for persistent blank contamination.
• DFA quantitation was compromised by matrix suppression in high-salt synthetic water and lack of a specific isotopically labeled surrogate; 13C2‑TFA was used as a proxy, degrading accuracy and precision for DFA.
• Retention-time stability was tested across RO water, synthetic water, and groundwater; synthetic water produced slight earlier shifts, while groundwater RTs matched RO standards closely.

Used Instrumentation

• LC: Agilent 1290 Infinity III
• MS: Agilent 6495D triple quadrupole operated in dynamic MRM
• Analytical column: Altura Poroshell PFAS column (2.1 × 100 mm, 2.7 µm)
• Delay column: Poroshell PFAS delay column (4.6 × 30 mm)
• Typical MS source/settings: gas temp ~240 °C, drying gas 18 L/min, sheath gas 350 °C at 11 L/min, nebulizer ~20 psig, Vcap 2000 V
• Chromatography: mobile phase A = 0.1% acetic acid in water; mobile phase B = 90:10 acetonitrile:water with 10 mM ammonium acetate; 0.5 mL/min flow; 25 µL injection; 40 °C column temperature; runtime ~12.5 min with a post time of 4 min

Main Results and Discussion

• Retention and separation: The Altura Poroshell PFAS column provided successful retention and chromatographic resolution for several ultra-short PFAS (C2–C3), which are typically poorly retained on standard C18 phases.
• Method detection limits (MDLs): Determined following EPA MDL procedures. Representative MDLs (ng/mL) included: DFA 0.008; TFA adjusted to 0.054 due to blank issues; PFMeS 0.007; PFPrA 0.005; PFOMAA, PFEtS, PFBA, PFPrS in the 0.004–0.005 range. TFA and PFMeS MDLs were impacted by background blank signals.
• Retention-time stability: Minimal RT variability for groundwater versus RO standards; synthetic high-salt water showed modest earlier RT shifts across peaks, indicating ionic-strength-dependent retention shifts but acceptable stability for groundwater testing.
• Matrix spike recovery and precision: In synthetic water spiked at three levels (lowest 0.01 ng/mL, except TFA at 0.1 ng/mL), most analytes showed recoveries within 70–130% and relative standard deviations (RSDs) <15%. Exceptions were DFA and TFA: DFA exhibited poor recovery (likely salt matrix suppression and no matched labeled surrogate), and TFA was affected by background contamination leading to poorer reproducibility.
• Field-sample comparison with EPA 1633A: Direct-injection PFBA results correlated strongly with collaborator data generated by EPA Method 1633A (solid-phase extraction-based), with a statistically significant correlation (p < 0.001). The comparison indicated comparable quantitative performance for PFBA between direct injection on Altura column chemistry and the established EPA method.

Benefits and Practical Applications

• Streamlined workflow: Direct injection minimizes sample preparation time, consumable use, and potential sample handling losses compared with SPE-based approaches.
• Sensitivity for ultra-short PFAS: Achieves low ng/L detection capability for multiple C2–C3 PFAS when column chemistry and MS parameters are optimized.
• Robustness for groundwater matrices: Demonstrated retention stability and comparable PFBA quantitation to EPA 1633A in landfill groundwater samples, supporting utility in environmental monitoring and site investigations.
• Operational considerations: Amenable to routine monitoring laboratories that can control ambient contamination and employ appropriate isotopically labeled surrogates for problematic analytes.

Future Trends and Potential Uses

• Broader adoption of PFAS-specific stationary phases for direct-injection workflows, enabling routine monitoring of ultra-short PFAS across environmental matrices.
• Development and availability of isotopically labeled standards for additional ultra-short analytes (e.g., DFA) to improve accuracy and precision in challenging matrices.
• Improved laboratory contamination controls and blank mitigation strategies to lower practical MDLs for ubiquitous analytes such as TFA.
• Integration with high-throughput monitoring programs and regulatory frameworks, where validated direct-injection methods can complement extraction-based standards for targeted analytes.
• Continued method comparison and inter-laboratory studies to establish equivalency and robustness across sites, instruments, and matrices.

Conclusions

The Altura Poroshell PFAS column combined with direct-injection LC–MS/MS on an Agilent 1290/6495D platform provides a practical, sensitive approach for analyzing ultra-short chain PFAS in groundwater and high-ionic-strength matrices. The method yielded low ng/L MDLs for most targets, acceptable spike recoveries and precision for the majority of analytes, and demonstrated comparable PFBA quantitation to EPA Method 1633A. Key limitations include ambient laboratory TFA contamination and challenges quantifying DFA without a matched labeled surrogate; addressing these will further improve method robustness.

References

1. U.S. Environmental Protection Agency. Method 1633A: Analysis of per- and polyfluoroalkyl substances (PFAS) in aqueous, solid, biosolids, and tissue samples by LC-MS/MS. EPA 820-R-24-007. 2024.
2. 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.
3. Agilent Technologies. Application Note: Reliable Ultra Short Chain PFAS Analysis in Water and Landfill Groundwater Using the Agilent Altura Poroshell PFAS column and LC/MS/MS. 5994-9019EN. 2026.