Dilution-Controlled PFAS Quantitation in Leachates by Automated SPE-LC-MS/MS

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

Prepared by N. Ruiz, O. Salawu, J. Borny
Lummus Technology, 13001 Bay Park RD, Pasadena, Texas, 77507, United States


Contact Information: [email protected]; 727-249-2516

ABSTRACT

Landfill leachate is a high ionic-strength, organic-rich matrix that can bias per- and polyfluoroalkyl substances (PFAS) quantitation by EPA Method 1633A through SPE flow restrictions, LC-MS/MS ion suppression, and poor recoveries. Although Method 1633A includes leachate, it does not specify matrix-specific controls such as dilution and cleanup thresholds needed to achieve stable isotope-dilution recoveries and bias control in highly suppressive industrial leachates, and few studies have reported these performance constraints. We evaluated an EPA 1633A implementation for industrial leachate using automated SPE with inline filtration/anti-clogging frits and isotope-dilution LC-MS/MS. Matrix effects were evaluated by comparing isotope-dilution recovery behavior across dilution factors and replicate leachate samples. Results obtained so far indicate that low dilution (2–10×) produced extreme responses for multiple analytes. PFBS and PFHxS returned recoveries orders of magnitude above typical acceptance windows. High solids produced recurrent SPE flow restriction, and pre-dilution improved cartridge performance; matrix suppression was tracked via internal-standard recovery monitoring. At higher dilution (100×–200×), recoveries stabilized across multiple PFAS classes. Extraction/injection-standard recoveries were generally near target ranges for PFBA (≈86–95%), PFOA (≈68–91%), PFOS (≈88–101%), and 4:2 FTS (≈80–86%), while native/internal-standard recoveries improved for PFOS (≈86–105%) and several carboxylates (e.g., PFHxA ≈82–91%; PFNA ≈79–93%). Overall, the results so far show that leachate PFAS measurements by EPA 1633A require matrix-adaptive operating conditions, with dilution and contamination control acting as primary determinants of recovery consistency and analytical bias control.