Determination of per- and polyfluorinated alkyl substances (PFAS) in drinking water

Significance of the topic

Perfluorinated alkyl substances are persistent environmental contaminants that pose health risks at low concentrations. Regulatory agencies have established stringent guidelines for monitoring PFAS in drinking water. Automated sample preparation enhances laboratory throughput and consistency compared to manual methods.

Objectives and study overview

This application note demonstrates a fully automated solid phase extraction procedure combined with liquid chromatography tandem mass spectrometry for accurate determination of twenty five PFAS in drinking water. The method follows US EPA Method 533 requirements for short chain PFAS with carbon chain lengths from four to twelve. Key goals include evaluation of system background, sensitivity, calibration, precision and accuracy in reagent and finished drinking water matrices.

Methodology and instrumentation Used

• SPE system AutoTrace 280 PFAS with anion exchange WAX cartridges
• Vanquish Flex UHPLC equipped with PFC free tubing and isolator column
• TSQ Fortis triple quadrupole mass spectrometer with negative H ESI source
• Acclaim 120 C18 analytical column and Hypersil BDS C18 isolator column
• Bench top Millipore Milli Q water purification system

Reagents and standards

• UHPLC MS grade water and methanol
• Optima LC MS ammonium acetate and acetic acid
• Native PFAS primary dilution standards spanning 500 to 5000 micrograms per litre
• Mass labelled PFAS isotope dilution and performance standards

Automated SPE workflow

Samples of 250 millilitres are spiked with primary standards and 250 milligram ammonium acetate. The AutoTrace 280 PFAS executes three sequential protocols: conditioning and loading with phosphate buffer and methanol, elution with ammoniated methanol, and automated path cleaning to avoid carryover. Extracts are evaporated to dryness and reconstituted with 80/20 methanol water prior to LC MS MS analysis.

LC MS MS conditions

The UHPLC gradient uses mobile phase A twenty millimolar ammonium acetate and mobile phase B methanol at 0.4 millilitres per minute and 45 degrees column temperature. A methanol flush and PFC free kit minimize background. The TSQ Fortis operates in negative ion mode with selected reaction monitoring transitions optimized for each PFAS compound over a 21 minute run time.

Calibration and quality control

Ten calibration levels from 0.1 to 100 micrograms per litre cover all target analytes. External performance standards and internal isotope dilution analogues ensure linearity with coefficients of determination above 0.99. LCMRLs are determined between 1.6 and 9.5 nanograms per litre. MDLs are calculated following seven replicate analyses at low concentration levels.

Main results and discussion

System background was minimal after blank extractions. Carryover was below one third of reporting limits. LCMRLs for the twenty five PFAS ranged from 1.6 to 9.5 nanograms per litre. Calibration curves achieved r squared values greater than 0.99 and mean deviations below 20 percent. Recovery tests in reagent water at 10 and 80 nanograms per litre yielded 86 to 124 percent recoveries with RSD below 18 percent. Tests in finished drinking water showed recoveries between 86 and 120 percent with RSD below 15 percent. Isotope dilution analogues demonstrated consistent accuracy and precision across matrices.

Benefits and practical applications

The automated SPE LC MS MS method meets US EPA Method 533 requirements while reducing manual labor, solvent consumption, and variability. It provides reliable quantitation of a broad panel of PFAS at trace levels in regulated drinking water monitoring and quality control laboratories.

Future trends and potential applications

Advances may include online SPE integration, further miniaturization of extraction formats, expanded target lists for newly identified PFAS, and coupling with high resolution mass spectrometry for non target screening. Green chemistry approaches to reduce solvent use and energy consumption may be incorporated for sustainability.

Conclusion

The presented automated SPE with LC MS MS workflow delivers robust, sensitive and reproducible determination of 25 PFAS in drinking water. It fulfills regulatory criteria and enhances laboratory productivity for environmental monitoring of persistent contaminants.

References

1 US EPA Method 533 Determination of Per and Polyfluoroalkyl Substances in Drinking Water by Isotope Dilution SPE and LC MS MS
2 Rahman MF Peldszus S Anderson WB Behaviour and Fate of PFAS in Drinking Water Treatment A Review Water Research 2014 50 318 340
3 Wilhelm M Bergmann S Dieter HH Occurrence of Perfluorinated Compounds in Drinking Water of North Rhine Westphalia Germany Int J Hyg Environ Health 2010 213 3 224 232
4 Ahrens L Taniyasu S Yeung LWY Yamashita N Lam PKS Ebinghaus R Distribution of PFAS in Water Suspended Particulate Matter and Sediment from Tokyo Bay Chemosphere 2010 79 3 266 272
5 Ullah S Alsberg T Berger U Simultaneous Determination of Perfluoroalkyl Phosphonates Carboxylates and Sulfonates in Drinking Water J Chrom A 2011 1218 37 6388 6395
6 US EPA PFAS Action Plan December 2019 Implementation of New Drinking Water Test Method
7 US EPA LCMRL Calculator Lowest Concentration Minimum Reporting Level Calculation Guidance