DETERMINATION OF LEGACY AND EMERGING PERFLUOROALKYL SUBSTANCES IN GROUND AND SURFACE WATERS USING LC-MS/MS FOLLOWING ENRICHMENT BY SPE

Significance of the Topic

PFAS are persistent environmental contaminants with widespread use as surfactants and in nonstick and water-resistant materials. Their stability and mobility lead to accumulation in surface and groundwater, posing risks to ecosystems and human health. Regulatory bodies in the US and Europe have established advisory levels in the low ppt range, driving the need for highly sensitive analytical methods.

Objectives and Study Overview

This study aimed to develop a comprehensive LC-MS/MS method for simultaneous determination of 40 legacy and emerging PFAS in ground and surface waters. The approach expands on ISO 25101 by incorporating weak anion exchange SPE enrichment and modern mass spectrometric detection to achieve sub-ppt sensitivity.

Methodology

• Water samples (surface, ground, influent and effluent wastewater) were acidified to pH<3, filtered, and subjected to SPE using Oasis WAX cartridges.
• Cartridges were conditioned with ammonia in methanol, methanol and water, loaded with sample, rinsed with acetate buffer and methanol, and eluted with ammonia in methanol.
• Eluates were evaporated to 0.5 mL and diluted with ammonium acetate before LC-MS/MS analysis, providing 250x enrichment.

Instrumentation Used

• LC system: ACQUITY UPLC I-Class Plus with PFC kit
• Column: ACQUITY UPLC BEH C18 2.1 x 100 mm, 1.7 µm (35 C)
• MS system: Xevo TQ-S micro with ESI source
• Operating conditions: capillary voltage 0.5 kV, desolvation temperature 350 C, source temp 100 C, desolvation gas flow 900 L/hr, cone gas flow 100 L/hr
• MRM transitions optimized via QuanOptimize in MassLynx

Results and Discussion

• Sensitivity and Linearity: Sample LODs ranged from <0.01 to 2 ng/L, with correlation coefficients above 0.99 for all compounds.
• Repeatability and Robustness: Six replicate analyses of spiked groundwater showed %RSDs below 15% (most below 10%). Twenty repeat injections of spiked surface water demonstrated stable peak areas and retention times with RSDs below 10%.
• Environmental Sample Analysis: Various PFAS were detected across sample types, confirming method applicability for monitoring surface water, groundwater, and wastewater matrices.

Benefits and Practical Applications

• The SPE enrichment approach delivers a 250-fold concentration factor, enabling detection at regulatory levels.
• The method is robust, reproducible and covers a wide range of legacy and emerging PFAS.
• Suitable for routine environmental monitoring and compliance with US EPA and EU water quality standards.

Future Trends and Opportunities

• Extension of the method to novel and unknown PFAS using high-resolution mass spectrometry and non-target screening.
• Automation and online integration of SPE for increased throughput.
• Development of miniaturized and field-deployable SPE-LC-MS/MS systems for on-site analysis.

Conclusion

The developed SPE-LC-MS/MS method provides sensitive, accurate and reproducible determination of a broad spectrum of PFAS in various water matrices, supporting regulatory compliance and environmental research.

Reference

• Waters Application Note 720006471EN