EPA Method 533

Matrix

Drinking water (finished/treated drinking water)

Analytes

25 PFAS analytes; focuses on shorter-chain PFAS (carbon chain lengths ~4 to 12). Together with Method 537.1, a total of 29 unique PFAS can be measured.

Status

Validated and EPA-published (2019). Uses isotope dilution to minimize matrix interference. Approved for compliance monitoring under the PFAS NPDWR and was used for UCMR 5. Current/active.

Official source

https://www.epa.gov/dwanalyticalmethods/method-533-determination-and-polyfluoroalkyl-substances-drinking-water-isotope

When to use EPA Method 533

Choose for drinking water when you need short-chain PFAS (e.g., PFBA, PFBS, GenX-related) and isotope-dilution data quality. Complements 537.1; many labs run both to capture the full 29-analyte combined list.

Not sure this is the right method?

Pick the method by your matrix first, then by data-quality needs. DRINKING WATER (tap, well, finished/treated water): use EPA Method 537.1 (18 PFAS, includes GenX) and/or EPA Method 533 (25 PFAS, short-chain focus, isotope dilution). Together they cover 29 unique PFAS, and both are EPA-approved for compliance monitoring under the PFAS National Primary Drinking Water Regulation. For a home/well drinking-water test, a lab certified for 537.1 and/or 533 is what you want. Method 537 (the original 2009, 14 analytes) is mostly historical -- prefer 537.1. NON-POTABLE / ENVIRONMENTAL samples (wastewater, surface water, groundwater, soil, sediment, biosolids/sludge, landfill leachate, fish tissue): use EPA Method 1633/1633A (40 PFAS, isotope dilution, multi-matrix; finalized Dec 2024 and proposed for CWA approval but not yet nationally mandated). For aqueous-only environmental screening under RCRA/SW-846, Method 8327 (24 PFAS, external standard) exists but is generally superseded by 1633 for serious work. Quick rule: drinking water = 533 + 537.1; everything else (soil/sludge/wastewater/tissue) = 1633.

Compare all methods on the PFAS testing overview.

Find a lab accredited for EPA Method 533

For DRINKING WATER PFAS testing, use a state-certified drinking-water laboratory: start at EPA's drinking-water lab certification page, which links to each state's certification program and lists of state-certified labs (EPA: 'Contact Information for Certification Programs and Certified Laboratories for Drinking Water'). Confirm the lab holds certification specifically for EPA Method 537.1 and/or 533 for the PFAS analytes you care about. For ENVIRONMENTAL/non-potable PFAS (soil, wastewater, biosolids, tissue), look for a lab accredited under TNI/NELAP for the relevant method (e.g., 1633, 8327) -- search the TNI LAMS (Laboratory Accreditation Management System) by lab name, state, accreditation body, and field of accreditation, and verify the specific PFAS analytes/method are listed in their scope. Always verify (1) the exact method, (2) the matrix, and (3) the specific analytes are on the lab's current accreditation/certification scope before sampling, since scopes change (e.g., many accreditation bodies added PFAS fields of accreditation effective Jan 1, 2025).

• TNI LAMS - National Environmental Laboratory Accreditation Management System (search for NELAP-accredited labs by name, state, accreditation body, and field of accreditation, including PFAS), National searchable database of TNI/NELAP-accredited environmental laboratories; filter for PFAS methods/analytes and matrices.
• NELAP Accreditation Bodies - The NELAC Institute (TNI), List of state and third-party NELAP accreditation bodies; useful for verifying a lab's accrediting authority and scope.
• EPA - Contact Information for Certification Programs and Certified Laboratories for Drinking Water, EPA hub linking to each state's drinking-water lab certification program and its list of state-certified drinking-water labs (use to find labs certified for Methods 537.1/533).