Performance of Commercial Labs in the Application of Per- and Polyfluorinated Alkyl Substance Measurement Methods for Industrial Matrices

Per- and Polyfluoroalkyl Substances (PFAS) in the Environment
Oral Presentation

Prepared by C. Lindelien, W. Kiridena, G. Johnson
NCASI, 14402 SW 3rd Blvd., Newberry, FL, 32669, United States


Contact Information: [email protected]; 352-244-0902

ABSTRACT

The utility of multiple methods for analyzing PFAS in complex aqueous and solid matrices was evaluated across several DoD-accredited laboratories using industry-sourced samples. Replicate untreated and treated pulp and paper wastewaters were analyzed using EPA Methods 1633A, 1621 (AOF), and the TOP assay. Primary and secondary biosolids, fly ash, compost, a reference standard, and spiked samples were analyzed using Method 1633A. The study assessed lab performance and compared Method 1633A to other non-targeted PFAS methods in complex matrices. The most notable insight is that variations in initial wastewater and solids handling can significantly impact results. Several laboratories sub-sampled or diluted wastewater samples in anticipation of TSS exceeding 50 mg (practices not recommended under Method 1633A). For solids, extraction masses varied by lab and matrix, leading to higher reporting limits, more non-detects, and greater variability in results. Initial comparisons with non-targeted methods highlight potential gaps and considerations when employing these methods as surrogate measures for PFAS. In these evaluations, the total mass percentage of fluoride quantified using Method 1633A accounted for only 3% (untreated wastewater) and 29% (treated wastewater) of the adsorbable organic fluoride quantified using Method 1621, indicating the presence of unidentified fluorinated compounds. Additional research is needed to assess potential biases introduced by inorganic fluoride that may not be fully removed before analysis. In the primary biosolid sample, spike recoveries for certain PFAS subgroups—particularly fluorotelomer carboxylic acids (FTCAs) and perfluoroalkyl ether sulfonic acids (PFESAs)—varied widely, with recoveries ranging from 25–276% depending on the compound and laboratory, likely due to matrix effects from protein and organic carbon interference. Additionally, the consistent overestimation of perfluorohexanesulfonic acid (PFHxS) analyte in the certified reference material highlights the possibility of inaccuracies in laboratory calibrations.