On average, current analytical methodologies measure a discrete list of 40 PFAS. Many additional PFAS are not determined as discrete compounds by existing commercial methods. Therefore, we may be underestimating the PFAS mass present in the environment. As the investigation and treatment of sites contaminated with PFAS matures, there is a growing interest in determining the contributions of different sources to the overall contamination and understanding the true mass of PFAS present. Eurofins has implemented several tools that illuminate additional pieces of the PFAS puzzle.
An initial aliquot of each sample is analyzed for a suite of targeted PFAS. A second portion of the sample is oxidized, extracted and analyzed for the same suite of PFAS and compared to the initial analysis. Increases in concentrations in the Perfluorocarboxylic Acids (PFCAs) indicate the presence of oxidizable precursors. The TOP Assay has revealed additional PFAS mass of up to 70% of fluorinated organics in AFFF impacted samples. Achievable detection limits as low as single digit part per trillion (ppt).
The determination of total organic fluorine approaches quantitation of the unknown mass of PFAS from the angle of the fluorine content of a sample. With the use of combustion ion chromatography (CIC) a wide range of matrices are analyzed for Total Organic Fluorine (TOF), Total Adsorbable OrganicFluorine (AOF) in water, or Extractable Organic Fluorine (EOF) in solids. Achievable detection limits are in the part per billion (ppb) range.
As AFFF and other PFAS sources have changed vendors and formulations over the years, the concentration and composition of PFAS in those products has also changed. As the number of targeted compounds increases, the likelihood of a unique identification increases. This is not to say that increasing from a list of 40 PFAS to 100 PFAS will elucidate a point source, only increase the potential for additional and unique positive identifications. Achievable detection limits as low as single digit part per trillion (ppt).
Different manufacturers and manufacturing processes produced varying ratios of branched and linear isomers of PFAS. Separate results of the linear isomer and the sum of branched isomers for PFOA, PFNA, PFOSA, PFHxS, PFOS, MeFOSAA, EtFOSAA, MeFOSA, EtFOSA, MeFOSE, and EtFOSE are possible. These data reported separately as Total Branched, Linear, and Total or “BLT” can yield more information than a single value would. While BLT assessments are nothing new for skilled PFAS researchers and laboratories, Eurofins is pleased to support a more refined BLT approach for PFOA which includes monitoring of additional ions of PFOA. This product offering is referred to as Forensic PFOA. Interested in learning more about Forensic PFOA? Click here.
While a long compound list and the ability to differentiate linear and branched isomers are powerful tools, there are estimated to be hundreds more PFAS in-use or with legacy usage. As there are only analytical standards for a fraction of these compounds, additional instrumentation is needed to identify PFAS without commercially available standards. This task is best suited for Quadrupole-Time-Of-Flight Mass Spectrometry (QTOF-MS) or an LC Orbitrap. This analysis results in exact mass data that can be compared to a library of exact mass spectra. This allows for unknown compounds to be identified with chemical formula, name, and CAS number when compared to publicly available spectral libraries such as NIST or FluoroMatch.