An Ultra-high Sensitivity Analysis of 29 PFAS Compounds in Drinking Water by Direct Injection

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are highly persistent environmental contaminants that pose significant health and regulatory challenges. Their use in firefighting foams, coatings, and various consumer products has led to widespread occurrence in water supplies. Analytical methods capable of detecting PFAS at sub-ng/L levels are critical for ensuring drinking water safety and compliance with stringent regulatory limits.

Objectives and Study Overview

This study aimed to develop and validate an ultra-high sensitivity direct injection method for simultaneous quantification of 29 PFAS in drinking water. Using the Shimadzu LCMS-8065XE system, the method seeks to achieve detection limits below 1 ng/L without sample preconcentration and a total run time of 18 minutes per cycle.

Methodology and Instrumentation

Samples were prepared by simple dilution in a 1:1 mixture of water and methanol, spiked with isotopically labeled internal standards at 10–40 ng/L. Chromatographic separation employed a Shim-pack Scepter C18 column (50 mm × 3 mm, 1.9 µm) with a matching delay column to minimize PFAS background. Mobile phases consisted of 2 mmol/L ammonium acetate in water (A) and methanol (B). The gradient delivered a full analysis in 18 minutes at 40 °C, with a 20 µL injection volume.

Used Instrumentation

• Shimadzu LCMS-8065XE triple quadrupole mass spectrometer
• StreamFocus ESI probe (negative ion mode)
• UFsweeper IV collision cell for enhanced sensitivity
• Shimadzu Nexera X3 UHPLC system
• Shim-pack Scepter C18-120 analytical and delay columns

Main Results and Discussion

The method detection limits (MDLs) for all 29 PFAS classes—including carboxylic and sulfonic acids, fluorotelomer sulfonates, and perfluoroalkyl ether acids—were below 1 ng/L. Specifically, PFOA and PFOS MDLs were 0.48 ng/L and 0.45 ng/L, respectively, well below the 4 ng/L EPA maximum contaminant level. Calibration curves over 1–100 ng/L demonstrated excellent linearity (R2 > 0.999) and accuracy within 80–120%. In fortified drinking water at 4 ng/L, recoveries ranged from 80% to 120% with repeatability below 20% RSD for all compounds.

Benefits and Practical Applications

• Direct injection simplifies sample preparation and reduces analysis time.
• High sensitivity meets or exceeds regulatory requirements for PFAS in drinking water.
• Short cycle time (18 minutes) allows high throughput in testing laboratories.
• Robust recovery and reproducibility support routine QA/QC and environmental monitoring.

Future Trends and Applications Possibilities

Ongoing developments may include further reduction of detection limits through enhanced ionization techniques, expansion to additional PFAS congeners, and automation of sample handling. Integration with online solid-phase extraction or high-resolution mass spectrometry could broaden applications to complex matrices such as wastewater and biota.

Conclusion

The described direct injection LC-MS/MS method on the Shimadzu LCMS-8065XE provides reliable, ultra-sensitive quantification of 29 PFAS in drinking water within an 18-minute run, without the need for preconcentration. It offers a practical solution for laboratories facing stringent regulatory demands and contributes to improved environmental and public health protection.