Contributed by Sarah Choyke

Sarah Choyke, Ph.D. is the Technical Director at Eurofins Environment Testing in Arvada, Colorado. She has 15 years of experience analyzing emerging contaminants in the environment with expertise in sample preparation, mass spectrometry, and analytical chemistry. She received her Ph.D. from Duke University (NC) and B.S. from Haverford College (PA).

Per- and polyfluorinated alkyl substances (PFAS) are a diverse class of synthetic fluorinated compounds known for their chemical stability and resistance to water (hydrophobicity) and oil (lipophobicity). These properties have made PFAS valuable in industrial manufacturing, certain firefighting foams, and a wide range of consumer products. However, decades of use have led to their pervasive presence in both industrial and residential waste streams. Today, municipalities and industrial dischargers face growing pressure to detect and manage PFAS in wastewater and biosolids.

Complex Matrices, Complex Challenges

Just as PFAS cannot be represented by a single compound, wastewater and biosolids encompass a broad spectrum of sample matrices. Influent and effluent may contain flocculant solids up to 5% while biosolids can range from liquid to dewatered or dried with moisture content spanning from 5-99%. These variations significantly affect the reliability and reproducibility of PFAS analysis.

Laboratory Tools and Limitation

PFAS Laboratories have limited but critical tools to mitigate matrix effects during sample extractions.

• For aqueous samples, subsampling or centrifuging can be used to reduce Total Suspended Solids (TSS).
• Subsampling maintains data integrity by representing the “whole bottle” but results in elevated reporting limits (RLs).
• Centrifugating preserves the lowest possible RLs but may compromise EIS recoveries due to sorption losses.
• For biosolid, physical removal of debris (large rocks, vegetation, invertebrates, foreign objects) and integration of pooled liquids ensure the extracted aliquot reflects the bulk material.
• The best way to ensure sample homogeneity and data quality is to use proper sampling techniques when collecting the sample.

The Gold Standard: Extracted Internal Standards

Quantitation using Extracted Internal Standards (EIS) remains the benchmark for PFAS analysis. This quantitation method relies on the recovery of isotopically labeled analogs (e.g., Carbon-13 and Deuterium) to internally quantify individual PFAS. It compensates for biases introduced during sample preparation and analysis due to matrix variability.

Partnering with Your PFAS Laboratory

PFAS Laboratories have highly skilled chemists, but they are not magicians. Clear communication and collaboration are essential – especially when dealing with complex matrices. Reach out to your lab if:

• Your aqueous samples contain unavoidable solids, perpetual colloids, or polymers.
• Your biosolids are viscous liquids or dried solids.
• Your samples have elevated PFAS concentrations (>10 ppb).
• Your samples are not homogeneous.
• You have specific reporting limits (RLs) or data quality objectives (DQOs) that must be met.

Ensure confidence in your PFAS results. Partner with Eurofins Environment Testing, with a dedicated PFAS-certified laboratory in Denver, CO, for expert guidance, robust methodologies, and reliable data across even the most challenging wastewater and biosolid matrices. Visit www.EurofinsPFAS.com.