EPA-OW/OST: 1621: Adsorbable organic fluorine (AOF) in aqueous matrices by Combustion Ion Chromatography (CIC)

Summary
Analytes
Revisions
Data and Sites

Official Method Name

Method 1621: Determination of Adsorbable Organic Fluorine (AOF) in Aqueous Matrices by Combustion Ion Chromatography (CIC)

Current Revision

Original method

Media

WATER

Instrumentation

Combustion Ion Chromatography

Method Subcategory

Organic

Method Source

EPA-OW/OST

Citation

Method 1621: Determination of Adsorbable Organic Fluorine (AOF) in Aqueous Matrices by Combustion Ion Chromatography (CIC)

Brief Method Summary

Aqueous samples are prepared and adsorbed using method-specific procedures. A sample aliquot of approximately 100 mL is passed through two GAC columns, each containing 40 – 50 mg of carbon. The GAC columns are rinsed with sodium nitrate to remove inorganic fluoride, combusted at ≥1000 °C in an oxygen or oxygen/argon stream, and the gaseous hydrogen fluoride is absorbed into reagent water. The fluoride is separated by ion chromatography (IC) and identified by comparing sample fluoride retention time to retention times for calibration standards acquired under identical IC conditions and quantified using the external standard technique.

Scope and Application

This method estimates the concentration of adsorbable organic fluorine (AOF) in aqueous matrices.

Applicable Concentration Range

A fluoride calibration range of approximately 2.0 µg F^- /L to 100 µg F^-/L (assuming a 100-mL sample volume) may be used as a starting point for determining the calibration range.

Interferences

(A) Interferences from artifacts in solvents, reagents, glassware, plasticware, and GAC column: Run a matrix/method blank. (B) Fluoride cross-contamination: Clean all equipment prior to, and after each use, to avoid fluoride cross-contamination. Typical cleaning solvents include water, methanol, and methanolic ammonium hydroxide (1%). (C) Fluoride contamination of glassware: It is highly recommended to avoid glass labware whenever possible. If any glass labware is used in the preparation or storage of reagents, the glassware must be cleaned by rinsing with methanolic ammonium hydroxide, followed by rinsing with reagent water, followed by a methanol rinse, and air drying. (D) Fluoride contamination of combustion boats: Boats should be cleaned by soaking in methanol for at least one hour, scrubbing with cotton swabs, rinsing with reagent water, and baking in a kiln or furnace at 450 °C for 1 hour, then stored in a desiccator or stored submerged in reagent water until use to prevent contamination from fluoride present in air particles. Prior to use, baked combustion boats must be rinsed with methanol and dried. If the combustion boats are stored longer than three days, then they must be baked again prior to use. (E) Clogging of gas adsorption tube: Use routine clean-up procedure. (F) Matrix interferences: No remedy. (G) Samples with total suspended solids above 100 mg/L: Use a piece of quartz wool as a prefilter (see method for cleaning and blanking). (H) Negative interference from alcohols, aromatic substances, carboxylic acids and organic carbon (> 140 mg/L): Assess effects by dilution or spiking of the sample. (I) High bias of inorganic fluoride: Nitrate wash (up to 8 mg/L) or dilution (>8 mg/L). (J) Coelution and adsorption site competition of chloride: No remedy. (K) Adsorption of organofluorines: No remedy.

Quality Control Requirements

Calibration standard solutions, Low-level and mid-level calibration verification (CV) standards, PFAS Standards, Chloride Stock Standard, Method blanks, ongoing precision and recovery (OPR) standards, Matrix spike (MS), Matrix spike duplicate (MSD).

Sample Handling

Collect approximately 100 mL of sample in an appropriately sized HDPE or polypropylene bottle. Samples that flow freely are collected as grab samples, or in refrigerated bottles using automated sampling equipment. Samples must be collected at least in triplicate to allow sufficient volume for the determination of total suspended solids, inorganic fluoride, residual chlorine, and pH, as well as having sufficient volume for matrix spikes or reanalysis. If a specific program requires the analysis of field replicates and/or spiked samples, additional containers must be collected. Maintain all aqueous samples protected from light at or below 6 ºC from the time of collection until shipped to the laboratory. Samples must be shipped as soon as practical with sufficient ice to maintain the sample temperature at or below 6 ºC during transport and be received by the laboratory within 48 hours of collection. The laboratory must confirm that the cooler temperature is at or below 6 °C upon receipt. If, upon receipt, the cooler temperature is above 6 ºC, the laboratory must contact the client for further guidance. Once received by the laboratory, the samples must be stored at or below 6 ºC until sample preparation.

Maximum Holding Time

Analyze as soon as possible though can be held protected from light up to 90 days when stored at or below 6 ºC.

Relative Cost

Sample Preparation Methods

Determine TSS, check/pre-treat for inorganic fluoride, residual chlorine, and pH.

This method has 1 analyte associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
Fluorine(7782-41-4) Fluorine	5.000 ug/L	92% Rec (ML)	12.40 % RSD (ML)			30.00 ug/L

Precision Descriptor Notes:	This method was validated, and performance specifications were developed using data from the EPA’s interlaboratory validation study (Reference 14 and attached in “revision” tab in NEMI). Table 1 provides the pooled MDL results from the multi-laboratory validation study. Data from all the QC samples in that study were used to develop the QC acceptance criteria in Table 3 (IPR/OPR) in all aqueous field samples. Table 4 provides results from the multi-laboratory validation study involving nine laboratories are only provided as examples for this method. The recovery and precision shown here are for POTW Effluent #1.
Detection Level Note:	This method was validated, and performance specifications were developed using data from the EPA’s interlaboratory validation study (Reference 14 and attached in “revision” tab in NEMI). Table 1 provides the pooled method detection limit (MDL) and Minimum Level (ML) for AOF determined during multi-laboratory validation study are provided as examples of method performance. (1) Fluoride concentration used to determine MDLs. PFHxS used as source of organofluorine. (2) Multi-laboratory validation study using 10 laboratories using PFAs-free reagent water with an organofluorine fortified concentration of 5.0 ug F^-/L. The pooled MDL is an estimate of the sensitivity that should be achievable in a well-prepared laboratory. The actual MDL generated in each laboratory should be used for data reporting and data quality assessments. (3) The Minimum Level (ML) in this table is derived as a multiple of the pooled MDL value and other derivations may apply. The actual ML generated in each laboratory should be used for data reporting and data quality assessments. Each laboratory must establish an MDL for organofluorine using the MDL procedure at 40 CFR Part 136, Appendix B. The MDL determination should be performed using perfluoro-1-hexanesulfonate (PFHxS) as the spiked compound. The concentration of each spiked MDL replicate is to be blank corrected using the average of the MDL blanks prepared and analyzed together with the spiked MDLs in each batch. The minimum level of quantification (ML) can be calculated by multiplying the MDL by 3.18 and rounding the result to the nearest 1, 2 or 5 x 10n, where n is zero or an integer.

Precision Descriptor Notes:

This method was validated, and performance specifications were developed using data from the EPA’s interlaboratory validation study (Reference 14 and attached in “revision” tab in NEMI). Table 1 provides the pooled MDL results from the multi-laboratory validation study. Data from all the QC samples in that study were used to develop the QC acceptance criteria in Table 3 (IPR/OPR) in all aqueous field samples. Table 4 provides results from the multi-laboratory validation study involving nine laboratories are only provided as examples for this method. The recovery and precision shown here are for POTW Effluent #1.

Detection Level Note:

This method was validated, and performance specifications were developed using data from the EPA’s interlaboratory validation study (Reference 14 and attached in “revision” tab in NEMI). Table 1 provides the pooled method detection limit (MDL) and Minimum Level (ML) for AOF determined during multi-laboratory validation study are provided as examples of method performance. (1) Fluoride concentration used to determine MDLs. PFHxS used as source of organofluorine. (2) Multi-laboratory validation study using 10 laboratories using PFAs-free reagent water with an organofluorine fortified concentration of 5.0 ug F^-/L. The pooled MDL is an estimate of the sensitivity that should be achievable in a well-prepared laboratory. The actual MDL generated in each laboratory should be used for data reporting and data quality assessments. (3) The Minimum Level (ML) in this table is derived as a multiple of the pooled MDL value and other derivations may apply. The actual ML generated in each laboratory should be used for data reporting and data quality assessments. Each laboratory must establish an MDL for organofluorine using the MDL procedure at 40 CFR Part 136, Appendix B. The MDL determination should be performed using perfluoro-1-hexanesulfonate (PFHxS) as the spiked compound. The concentration of each spiked MDL replicate is to be blank corrected using the average of the MDL blanks prepared and analyzed together with the spiked MDLs in each batch. The minimum level of quantification (ML) can be calculated by multiplying the MDL by 3.18 and rounding the result to the nearest 1, 2 or 5 x 10n, where n is zero or an integer.

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Original method
Single-laboratory validation study
Multi-laboratory validation study

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EPA-OW/OST: 1621: Adsorbable organic fluorine (AOF) in aqueous matrices by Combustion Ion Chromatography (CIC)

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