Incorporating Ultrashort-Chain Compounds into the Comprehensive Analysis of PFAS in Potable and Non-Potable Waters

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are globally recognized contaminants. Ultrashort-chain (USC) PFAS (C1–C3) present new analytical challenges due to their high polarity and low retention in conventional reversed-phase methods. These compounds occur frequently in potable and non-potable waters and may pose health and ecological risks. A comprehensive analytical workflow that covers both USC and longer-chain PFAS is therefore critical to fully assess environmental exposure and support regulatory monitoring.

Objectives and Study Overview

This study aimed to develop and validate a simple, reliable dilute-and-shoot LC-MS/MS method for the simultaneous quantification of 45 PFAS, including C1–C14 perfluoroalkyl carboxylic acids, sulfonic acids, fluorotelomer derivatives, and ether PFAS. The workflow was tested across diverse water matrices, including tap water, bottled water, wastewater effluents, well water, spring water, and creek water, to demonstrate broad applicability and performance consistency.

Methodology and Instrumentation

Sample Preparation and Standards:

• Calibration range: 1–1000 ng/L in reverse-osmosis water, fortified with labeled internal standards (QIS) for quantification.
• Samples (tap, bottled, POTW effluent) were analyzed directly or filtered, spiked at 2–250 ppt with native analytes, surrogate TFA, and QIS/EIS, then mixed with methanol (1% acetic acid).

Instrumental Setup:

• Liquid Chromatography: Waters Acquity UPLC with Ultra Inert IBD column (100 × 2.1 mm, 3 µm) and PFAS delay column.
• Mobile phases: 5 mM ammonium formate/0.1% formic acid in water (A) and acetonitrile (B); gradient ramp from 50% to 95% B.
• Mass Spectrometry: Waters Xevo TQ-S triple quadrupole with negative ESI, scheduled MRM; 45 transitions optimized for precursors, products, cone and collision voltages.
• Injection volume: 45 µL; flow rate: 0.4 mL/min; column temperature: 40 °C.

Main Results and Discussion

Chromatographic Performance:
The inert-coated polar-embedded column provided 3–75% improvement in peak area and height versus uncoated hardware. All 45 PFAS showed baseline separation across C1–C14.

Linearity, Accuracy and Precision:

• Quadratic calibration (1/x weighting) yielded r2 > 0.995 for all analytes over 1–1000 ppt, with ≤30% deviation at the lowest level.
• Recovery across fortified levels (2–250 ppt) ranged from 70% to 130% and RSD ≤ 20% (n=9 replicates).
• Surrogate and extracted internal standards recovered within ±30% of nominal concentration, confirming reliable quantification.

Application to Real-World Samples:
Triplicate analyses of various water matrices demonstrated consistently accurate PFAS measurement. Ultrashort-chain PFAS (TFA, PFPrA, PFBA) and longer-chain analytes were detected in tap, bottled, effluent, and environmental waters, illustrating method robustness.

Benefits and Practical Applications

This dilute-and-shoot workflow eliminates time-consuming extraction, reduces solvent use, and simplifies sample handling. The broad analyte scope enables comprehensive monitoring of legacy and emerging PFAS in drinking water safety, wastewater treatment assessments, environmental surveys, and industrial discharge control.

Future Trends and Applications

Emerging needs include routine monitoring of ultrashort-chain PFAS at sub-ppt levels and identification of novel polyfluorinated alternatives. Future developments may integrate high-resolution MS for suspect screening, automated sample preparation for higher throughput, and miniaturized field-deployable devices. Regulatory pressures will drive method standardization and interlaboratory validation.

Conclusion

A simple, sensitive, and precise LC-MS/MS dilute-and-shoot method was established for comprehensive PFAS analysis from C1 to C14. The inert-coated polar-embedded column provided improved retention and sensitivity, while calibration, accuracy, and precision metrics met stringent requirements. Successful application across a wide range of water matrices demonstrates the method’s utility for environmental monitoring and regulatory compliance.