PFAS Non-targeted Analysis
Thu 24 Apr, 2025
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The Promising Potential of EOF and AOF as Sum Parameters
PFAS are a hot topic in industry, laboratories, consumer protection, or politics. The focus on these chemicals is steadily increasing, along with the call for stricter regulations and precise analysis methods.
What are PFAS?
Per- and polyfluoroalkyl substances (PFAS) are a class of synthetic non-aromatic chemicals containing multiple fluorine atoms attached to the alkyl chain. As a part of everybody’s daily life, these chemical substances have been increasingly used in various industries since the 1960s, including the manufacturing of textiles, paper, and food packaging, as well as for semiconductor production and car tires. The reason for their versatile use lies in their chemical stability: The “forever chemicals” are resistant to heat, oil, stains, grease, and water.
Consequently, the highly persistent PFAS are identified as environmental pollutants, with some exhibiting adverse effects on human health. Once released into the environment, PFAS can enter the groundwater and soils. Certain PFAS have already been detected in humans and animals at very low levels.
Challenges
The presence of these substances is concerning due to their harmful risk to health. The two best known examples, PFOA (perfluorooctanoic acid) and PFOS (perfluorooctanesulfonic acid), are classified and regulated as persistent organic pollutants (POP) in the Stockholm Convention. At a European level, this applies to several other substances of PFAS. Within the next years, restrictions and prohibitions will be tightened, e.g., as of 2026 drinking water in Germany must be tested for a group of 20 PFAS substances to guarantee compliance with the cumulative limit value of 0,1 µg/L.1
The numerous different substances and their mostly still unknown effects on humans and the environment highlight the urgency to improve the monitoring of PFAS. Besides the screening of surface water or soils, monitoring at wastewater treatment plants is of increasing interest.
However, there are several challenges to consider: The determination of individual compounds is time-consuming and costly. Moreover, the methods applied must be able to detect the smallest quantities (ng/L). Certain chemicals that are already known can be analyzed using target analysis. In addition, the analysis of the sum parameters AOF and EOF also offers practical approaches to detect the presence of PFAS chemicals (non-target analysis). Both methods are examined in more detail below.
Target analysis to quantify PFAS and its limitations
Target analysis has proven itself for a range of applications and matrices. In this approach, chromatographic separation of the components using high-performance liquid chromatography (HPLC) is combined with tandem mass spectrometry (LC-MS/MS). In water analysis, enrichment by solid phase extraction (SPE) is also frequently carried out. In this way, values below 1 ng/L (in water) can be achieved.
However, the method reaches its limits regarding the quantity of PFAS compounds: The number of target analytes (targets) is usually limited to 20 to 30 specific PFAS. This includes the most commonly used and potentially most hazardous PFAS substances. LC-MS/MS is also limited to 30 to 50 specific compounds in order to obtain meaningful results. Beyond this defined group, there are many other PFAS substances in the environment, the number of which has not yet been uniformly defined. Depending on the interpretation of the definition, the number varies between 5,000 and millions. This means that even under ideal conditions, more than 99% of PFAS cannot be detected by target analysis.
Sum parameter analysis for PFAS monitoring
For the fast screening of PFAS-contaminated environmental samples the sum parameters AOF (adsorbable organically bound fluorine) and EOF (extractable organically bound fluorine) which are associated with the TOF (total organically bound fluorine) are suitable. This solution offers the benefits of minimal sample preparation and quick results, enabling rapid risk assessment and evaluation of the need for further compound-specific analysis (target PFAS testing).
AOF sum parameter analysis
Adsorbable organically bound fluorine (AOF) covers all organic fluorine compounds, including PFAS which are adsorbable on activated carbon. Elemental analysis with pyrohydrolytic combustion combined with ion chromatography (CIC) is a common solution for the determination of AOF. CIC can provide a fast and accurate picture of the overall contamination levels before performing targeted analysis to identify individual PFAS compounds.
In this method, organically bound fluorine is adsorbed on activated carbon either by column or batch method. The inorganic fluorine compounds are rinsed-off by a suitable wash solution. The prepared samples are combusted at high temperatures (≥ 950 °C) in an oxygen atmosphere with the addition of water (pyrohydrolysis). Organic fluorine compounds are combusted to hydrogen fluoride (HF), which is absorbed in aqueous solution and detected as fluoride (F-) by ion chromatography. Combustion and detection can be coupled (on-line) as in a CIC system or performed independently (off-line) by separate combustion and IC systems.
To ease the workflow of monitoring AOF, Analytik Jena offers standardized sample preparation systems for the entire process of AOF sample preparation (acc. to DIN 38409-59, ISO/DIS 18127, EPA 1621) and related consumables:
- For fast preparation of smaller sample series, the APU sim is ideal: The system prepares up to six AOF samples simultaneously using the column method, making it especially suitable for small sample series.
- The user-friendly APU 28 connect series enables the fully automated enrichment of up to 28 samples according to column resp. solid phase extraction (SPE) method. Its touch display enables intuitive operation and sample preparation with minimal effort.
EOF sum parameter analysis
The sum parameter EOF (extractable organically bound fluorine) is another approach for time-saving risk assessment of samples and complements the AOF approach in screening tasks for contamination of samples with organically bound fluorine compounds.
A simple, cost-effective and time-saving quantification of fluorine in EOF samples is provided by molecular absorption spectrometry (MAS). The unique design of the contrAA 800 high-resolution continuum source atomic absorption spectrometer (HR-CS AAS) allows quantification of both molecular absorption and atomic absorption lines. By adding a suitable molecule-forming reagent, CaF or GaF molecules are generated under optimised conditions and used to determine the fluorine content. The graphite furnace technique allows very sensitive fluorine quantification in the µg L-1 range in suitable matrices.
Conclusion
The potentially toxic effects of PFAS on living organisms and the environment call for fast and reliable monitoring solutions of these substances in waters and soils. Next to the commonly used, however limited approach of PFAS target analysis, the screening using sum parameters EOF and AOF have proven to be reliable methods for the rapid monitoring of organically bound fluorine, such as PFAS. With minimal sample preparation, results are quickly available, allowing for a prompt assessment of further analysis requirements. Analytik Jena supports laboratories in this field with precise, user-friendly, and cost-effective analytical instruments.
Customer Story
Award-Winning Research in the Field of PFAS
Bunsen-Kirchhoff Prize winner Dr. Björn Meermann from the German Federal Institute for Materials Research and Testing (BAM) conducts research in the field of analyzing per- and polyfluorinated alkyl compounds (PFAS). In the video customer story, you gain exciting insights into his research work with our contrAA 800 atomic absorption spectrometer.
References
1 Drinking Water Ordinance of 20 June 2023 (Federal Law Gazette 2023 I No. 159). Available at https://www.gesetze-im-internet.de/englisch_trinkwv/englisch_trinkwv.html#p0096
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Determination of PFAS in Soil and Sewage Sludge as a Sum Parameter EOF (Extractable Organically Bound Fluorine) (EN)
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Bestimmung von PFAS in Böden und Klärschlämmen als Summenparameter EOF (extrahierbares organisch gebundenes Fluor) (DE)
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Sample Preparation for the Determination of AOF in Water Samples According to E DIN 38409-59 (EN)
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Probenvorbereitung für die Bestimmung des AOF in Wässern nach E DIN 38409-59 (DE)
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Brochure contrAA800 (EN)
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Broschüre contrAA800 (DE)
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Flyer AOF Sample Preparation - APU Systems (EN)
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Flyer APU sim (EN)
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Flyer APU 28 connect (EN)
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