EPA 533 was published in 2019 specifically to cover the short-chain PFAS replacement chemistries (HFPO-DA / GenX, ADONA, 9Cl-PF3ONS) that the older 537.1 method couldn't capture. The 25-analyte list includes:
The method uses isotope-dilution direct injection — no solid-phase extraction step — which simplifies the workflow and reduces blank contamination risk. Sub-ppt sensitivity (typically 1-2 ng/L MDL per analyte).
Use EPA 533 when: testing finished drinking water for NPDWR compliance, UCMR5 monitoring, or any modern PFAS exposure assessment that needs the short-chain replacement chemistries.
EPA 537.1 (published 2018, with 537 originally from 2009) is the longer-chain legacy method:
Use EPA 537.1 when: required for state-program comparability (some state agencies still specify 537.1 by name), for a particular analyte not in the 533 list, or when the source water has historical 537.1 data that needs to be tracked over time.
Finalized in 2024 as part of EPA's PFAS Strategic Roadmap, Method 1633 extends PFAS quantitation to non-drinking-water matrices:
Use EPA 1633 when: testing wastewater (NPDES permit characterization), soil or sediment (Superfund site assessment, AFFF firefighting-foam impact zones), biosolids (Class A / B sewage sludge land-application permits), or fish tissue (state advisory programs).
EPA finalized the National Primary Drinking Water Regulation for PFAS in April 2024. The rule sets federal MCLs for six PFAS:
Public water systems must complete initial monitoring by 2027 and reduce concentrations to compliance by 2029. The required reference method is EPA 533 or EPA 537.1; either is acceptable.
A defensible PFAS COA from any of the three methods includes:
PFAS analytical chemistry has a particularly hostile blank problem. PFAS are everywhere: in the analytical workflow itself (Teflon-coated tubing, sample bottles, lab equipment), in the analyst's clothing (water-repellent jacket coatings, Gore-Tex), and in the water supply of the lab building. A credible lab takes all-PFAS-free containment seriously — HDPE bottles only, no fluoropolymer tubing, separate analytical bench from other chromatography work, dedicated solvent supplies.
When evaluating a PFAS COA from any lab, the method-blank result and the field-blank result are the first things to check. If those aren't reported, the lab probably isn't running them — and PFAS results without blank documentation aren't defensible.
EPA 533 is the modern drinking-water method covering short-chain PFAS including the 2024 NPDWR-regulated analytes. EPA 537.1 is the legacy long-chain drinking-water method. EPA 1633 extends to wastewater, soil, biosolids, and tissue for non-potable matrices. All three use isotope-dilution LC-MS/MS quantitation at ppt sensitivity. A credible COA reports method-blank, field-blank, and isotope-labeled internal-standard recovery per analyte.
See our drinking water + food & beverage testing for the full PFAS panel pricing, or the environmental overview.
