PFAS EPA Method 1633: Answers to six key questions

In tandem with the publication of the roadmap, EPA Office of Water has finalized Method 1633 “Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/ MS².

There are many lingering questions about the method – how it should be approached in the short term, and planning for its long-term adoption.

These are answers to six of the most frequently asked questions on EPA Method 1633.

What is the purpose of the new method?

The need for standard PFAS methods for different matrices became clearer as the ubiquitous nature of PFAS in environmental media and wastes was better understood. EPA Method 1633 is intended to provide standard procedures for the sampling and analysis of PFAS in a wide range of sample types: surface water, groundwater, wastewater, leachate, fish tissue, soil, sediment, and biosolids. It also analyzes for a larger number of PFAS compounds – 40 in total, and uses isotope dilution techniques to more accurately quantify PFAS.Additionally, Method 1633 addresses analytical challenges that are unique to PFAS, such as:

• Linear and branches isomer occurrence for some PFAS
• False-positive results for PFOS
• Aqueous samples with particulates
• Precursor transformations during sample preservation and storage
• PFAS adherence to the sample container wall and stratification within the container

It is hoped that the success of Method 1633 in addressing these analytical challenges will help to address them in other PFAS methods.

Will this method replace EPA Method 537.1 or EPA 533?

EPA Method 1633 complements, but does not replace, existing PFAS methods such as:

• Safe Drinking Water Act (SDWA) Method 537.1 for finished, potable water
• SDWA Method 533 for finished, potable water
• Resource Conservation and Recovery Act (RCRA) SW846 Method 8327 for groundwater, surface water, and wastewater

EPA Method 1633 has been developed for non-drinking water aqueous matrices (surface water, groundwater, wastewater influent/effluent, landfill leachate), fish tissues, biosolids, soils, and sediments. It complements existing PFAS methods by analyzing a larger number of PFAS compounds and a greater variety of sample matrices.

In summary:

• EPA Method 1633 is a multi-laboratory validated method that has been specifically designed for wastewater analysis. It is endorsed by the EPA.
• Modified EPA Method 537.1 and EPA Method 533 are drinking water methods that may be adapted for wastewater analysis. While acceptable for SDWA testing, they may not be appropriate for wastewater analysis because they have not been validated for wastewater matrices.

What compounds are covered under EPA Method 1633?

EPA Method 1633 analyzes over 40 PFAS compounds, including:

Timeline of PFAS Methods

What programs are requiring Method 1633?

Currently, EPA Method 1633 is yet not required for PFAS compliance monitoring by any EPA regulation, although it is the preferred method for some programs, including NPDES.

The National Pollutant Discharge Elimination System (NPDES) recommends using EPA Method 1633 for analyzing PFAS in permits. This is because there are currently no approved PFAS methods in 40 CFR Part 136.

Facilities with a federally issued NPDES discharge permit can use Method 1633 for permit application testing and ongoing discharge monitoring. Additionally, states issuing NPDES permits will receive guidance from EPA recommending the use of Method 1633.

The DoD Environmental Data Quality Workgroup has determined that EPA Method 1633 meets the precision, accuracy, and limits of quantitation needed to support sound decision making. All new contracts and task orders after December 31, 2021, shall require the use of Method 1633 for the analysis for PFAS in matrices other than drinking water using a laboratory accredited to the method/matrix/analyte by the DoD Environmental Laboratory Accreditation program (ELAP). All existing projects are encouraged to use Method 1633 for PFAS analysis in matrices other than drinking water when ELAP-accredited laboratories become available.

Are federal agencies and states offering accreditation for EPA Method 1633?

EPA does not currently regulate PFAS under the Clean Water Act, meaning there are no laboratory certification requirements for PFAS analysis at this time. The U.S. Department of Defense (DOD) has a PFAS laboratory certification program through its Environmental Laboratory Accreditation Program (ELAP).

States tend to certify laboratories in order to support the monitoring of federally regulated contaminants. As a result, most states have yet to develop a PFAS laboratory certification program. Some state agencies, such as the Alaska Department of Environmental Conservation, are certifying PFAS laboratories based on their DOD-ELAP accreditation. Some states such as the Commonwealth of Pennsylvania are offering certification for the draft version.

Does the method include changes in sampling, preservation, or hold times?

Yes, Method 1633 has requirements for sample container, preservation, temperature, and holding time that differ from existing methods. The following table lists the requirements for aqueous samples for Method 1633 and existing drinking water methods.

PFAS EPA Methods - Sampling Requirements

How will the transition to Method 1633 affect sample turnaround time and lab capacity?

EPA Method 1633 is more intensive for the laboratory in two primary ways: first, there are more target analytes (40 compared to the current 14-25); second, the quality control criteria is more stringent than existing methods. Both of these aspects of the draft method have the potential to impact a laboratory’s capacity and sample turnaround time. EPA Method 1633 enables expanded characterization of more PFAS compounds in more matrices. It is without a doubt the method of the future!

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