Analysis of Perfluorinated Alkyl Acids Specified in EPA M537 and Beyond Using the Triple Quad LCMS-8045

Significance of Topic

Perfluorinated alkyl substances (PFAS) are persistent environmental pollutants with documented health risks. Their widespread presence in drinking water and resistance to conventional treatment demand highly sensitive and reliable analytical protocols. Regulatory guidance such as EPA Method 537 mandates trace-level quantitation of perfluorinated alkyl acids (PFAAs), driving the need for robust liquid chromatography–tandem mass spectrometry (LC-MS/MS) workflows capable of meeting strict performance criteria.

Goals and Study Overview

This study aimed to implement and validate an expanded PFAS panel—including both PFAAs specified in EPA Method 537 and additional fluorotelomer sulfonates and alcohols—using the Shimadzu LCMS-8045 triple quadrupole system. Key objectives were to optimize sample preparation, chromatographic separation, and mass spectrometric detection to achieve low-ppt detection limits, high recovery, and regulatory compliance.

Methodology and Used Instrumentation

Sample Preparation via Solid-Phase Extraction

• Cartridge: Biotage® ISOLUTE® 101 polystyrene-divinylbenzene (SDVB)
• Conditioning: Methanol then LC-MS grade water
• Sample Volume: 250 mL drinking water fortified with isotope surrogates
• Elution: 8 mL methanol, evaporation under nitrogen, reconstitution to 1 mL in 96:4 MeOH:H₂O with internal standards

Chromatography and Detection

• Column: Restek Raptor ARC-18, 150 × 2.1 mm, 1.8 µm
• Mobile Phases: A = 20 mM ammonium acetate in water; B = methanol
• Gradient Elution: Optimized to resolve PFOS and PFHxS isomers
• Mass Spectrometry: Shimadzu LCMS-8045 triple quadrupole, MRM transitions optimized by flow injection analysis

Main Results and Discussion

Calibration and Linearity

• Ten calibration levels from 1.25 ppb to 100 ppb
• Coefficient of determination (R²) > 0.994 for all analytes

Method Detection Limits

• MDLs ranged between 0.69 ppt and 3.25 ppt, well below regulatory thresholds

Recovery, Precision, and Accuracy

• Extraction recoveries exceeded 80% for all target compounds
• Surrogate recoveries within ±10% of theoretical values
• Precision (%RSD) and accuracy met EPA 537 criteria across low, mid, and high concentration levels

Isomer Separation
Baseline chromatographic resolution of PFOS and PFHxS isomers was achieved, enhancing confidence in quantitation of structurally similar species.

Benefits and Practical Applications of the Method

This LC-MS/MS approach delivers:

• Regulatory compliance for drinking water monitoring under EPA Method 537
• High sensitivity for trace-level PFAS detection
• Robust performance across extended PFAS panels
• Isomeric resolution to distinguish critical isomers

It is suitable for environmental testing laboratories, QA/QC programs, and research settings where reliable PFAS quantitation is required.

Future Trends and Potential Uses

Upcoming developments may include:

• Incorporation of novel and emerging PFAS compounds into standard panels
• High-resolution mass spectrometry and non-target screening for unknown PFAS identification
• Miniaturized and automated SPE workflows for higher throughput
• Field-deployable mass spectrometry platforms for on-site monitoring

Conclusion

The combined SPE–LC-MS/MS workflow using Shimadzu LCMS-8045 and Biotage® ISOLUTE 101 cartridges surpasses EPA 537 performance requirements. With MDLs below 3.3 ppt, recoveries above 80%, and strong precision and accuracy, the method provides a reliable solution for comprehensive PFAS analysis in drinking water.

Reference

• U.S. EPA Method 537: Determination of Selected Perfluorinated Alkyl Acids in Drinking Water
• 40 CFR Part 136, Appendix B: Definition and Procedure for the Determination of the Method Detection Limit
• Wellington Laboratories: Certified PFAS standards