Draft:EPA Method 1621

EPA Method 1621 is an analytical method developed by the United States Environmental Protection Agency (EPA) for measuring adsorbable organic fluorine (AOF) in aqueous environmental samples. The method uses adsorption onto granular activated carbon followed by combustion and analysis using ion chromatography to estimate the total concentration of organofluorine compounds present in water. These compounds include many per- and polyfluoroalkyl substances (PFAS) as well as other fluorinated organic chemicals.

EPA Method 1621 is intended as a screening technique to estimate the overall burden of fluorinated organic contaminants in environmental waters and wastewater when individual compounds may not be fully identified.[1]

Background

Thousands of fluorinated organic chemicals exist, including many PFAS compounds used in industrial processes, consumer products, and firefighting foams. Conventional targeted analytical methods typically quantify only a limited number of individual PFAS compounds. As a result, screening approaches such as AOF and total organic fluorine analysis have been developed to estimate the overall quantity of fluorinated organic substances present in environmental samples.[2]

Mass‑balance approaches such as AOF, extractable organic fluorine (EOF), and total fluorine analysis are increasingly used to identify unidentified fluorinated compounds in environmental samples and evaluate the completeness of targeted PFAS analysis.[3]

Principle of the method

EPA Method 1621 measures adsorbable organic fluorine through a multi‑step analytical procedure:

  1. Water samples are passed through columns containing granular activated carbon (GAC).
  2. Organofluorine compounds are adsorbed onto the activated carbon.
  3. A nitrate wash removes inorganic fluoride that may interfere with measurement.
  4. The activated carbon is combusted at high temperature.
  5. Fluorinated organic compounds are converted to fluoride ions.
  6. Fluoride ions are measured using ion chromatography.

Results are typically reported as micrograms of fluoride per liter (µg F⁻/L).

Analytes

The method captures fluorinated organic compounds that adsorb onto activated carbon. These include many PFAS compounds such as:

Other fluorinated compounds including certain pesticides and pharmaceuticals may also contribute to measured AOF.

Sample types

EPA Method 1621 is designed for analysis of aqueous environmental samples including:

  • Wastewater influent and effluent
  • Industrial discharge samples
  • Surface water
  • Environmental monitoring samples

Instrumentation

Typical instrumentation used for EPA Method 1621 includes:

Combustion ion chromatography system

Adsorption equipment

  • Granular activated carbon (GAC) columns
  • Column holders and flow control systems
  • Sample introduction tubing and valves

Combustion components

  • Quartz combustion boats
  • Pyrolysis tube
  • Oxygen supply
  • Gas flow controllers

Reagents and consumables

Typical reagents and laboratory consumables include:

  • Granular activated carbon
  • Nitrate wash solutions used to remove inorganic fluoride
  • Fluoride calibration standards
  • PFAS‑free sample containers
  • Volumetric flasks and pipettes

Quality control

EPA Method 1621 includes quality assurance procedures commonly used in environmental analytical chemistry, including:

  • Calibration verification standards
  • Method blanks
  • Matrix spike samples
  • Ongoing precision and recovery samples

These procedures help verify analytical accuracy and minimize contamination during PFAS‑related analysis.

Interferences

Potential analytical interferences may include:

  • High concentrations of inorganic fluoride
  • Elevated chloride concentrations
  • Organic compounds competing for adsorption sites on activated carbon
  • Background fluorine contamination from laboratory materials

Proper washing procedures and contamination controls are required to minimize these effects.

Applications

EPA Method 1621 is used in environmental monitoring programs and research related to fluorinated contaminants. Applications include:

  • PFAS contamination screening
  • Industrial discharge monitoring
  • Wastewater treatment studies
  • Environmental research on fluorinated organic compounds

The method provides an aggregate measurement of organofluorine contamination and does not identify individual PFAS compounds.

See also

References

  1. ^ Report on the Single-laboratory Validation of Clean Water Act Method 1621 for Adsorbable Organic Fluoride (AOF) (Report). U.S. Environmental Protection Agency. April 2022.
  2. ^ Buck, Robert C. (2011). "Perfluoroalkyl and polyfluoroalkyl substances in the environment: Terminology, classification, and origins". Environmental Science & Technology.
  3. ^ Reconciling Terminology of the Universe of Per‑ and Polyfluoroalkyl Substances (PFAS) (Report). Organisation for Economic Co‑operation and Development (OECD). 2021.

Public Domain This article incorporates public domain material from websites or documents of the United States Environmental Protection Agency.

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