Total Organofluorine (TOF) Analysis
Per- and polyfluorinated alkyl substances (PFASs) are known as forever chemicals as they accumulate in the environment and are an increasing concern to international health authorities.
Our Targeted Method
RPS, a Tetra Tech company, have developed a targeted method to detect 54 PFAS compounds in one analysis, but this is only a small percentage of the known 10,000 PFAS substances. There is a growing interest in determining the total PFAS loading of a sample
as most PFAS compounds are over 60% fluorine by mass e.g. PFOA and PFOS are 68.8% and 64.6% fluorine, respectively. Total fluorine (TF), total organic fluorine (TOF), extractable organic fluorine (EOF) or adsorbable organic fluorine (AOF) analyses are indicative tests that can be used to suggest the total PFAS loading of a sample.
Total Organofluorine (TOF)
TF is the total amount of fluorine that is found within a sample. This is a combination of both inorganically bonded fluorine, like NaF or CaF2, and the organically bound fluorine, like PFASs or fluoropolymers. Accurate analysis of this can be performed by using
Combustion Ion Chromatography (C-IC). Total inorganic fluorine (TIF) is analysed directly by Ion Chromatography, which can be subtracted from the TF to obtain TOF. Reporting limits for TOF of as low as 1 mg F/kg can be achieved in solid matrices such as sludges, biosolids, consumer products and packaging or AFFFs. Reporting limits for liquid matrices are 0.5 mg F/L.
EOF involves a matrix specific extraction methodology used in our laboratory for our accredited targeted PFAS analysis, to extract and concentrate organic fluorine compounds. An aliquot of this extract is analysed by C-IC, with achievable reporting limits of 0.05 mg F/L or 0.1 mg F/kg. For AOF, 100 mL of a liquid sample is passed through an activated carbon cartridge, where only the organic fluorine is adsorbed onto the cartridge and any inorganic fluorine is washed off using a nitrate solution. These activated carbon cartridges are analysed by C-IC, with reporting limits of 0.002 mg F/L.
Combustion Ion Chromatography
Combustion Ion Chromatography (CIC) works by introducing a solid or liquid sample into a quartz combustion tube placed in an oven at over 1000oC, where the sample is pyro-hydrolysed, combusted in
the presence of oxygen and water. This creates gaseous hydrogen fluoride compounds which are then sparged into the absorber solution
where the Fluoride ions dissociate. This solution is then analysed using Ion Chromatography.
Benefits of C-IC:
- Indicative of the full PFAS loading of the sample.
- More time and cost-effective analysis compared to LC-MS/MS analysis and data processing which can be expensive and time consuming.
- For TF and TOF, there is very little sample preparation involved but can indicate if high levels of PFAS could be present.
- For EOF and AOF, more sample preparation is require but more PFAS specific information can be gained with lower reporting limits compared to TF or TOF.
Negative of C-IC:
- These tests are not compound specific, and gives no specific information to which PFAS compounds may be present within the sample, this is only achievable by LC-MS/MS.
Accreditations
Key contacts
Marco Lattughi
Operational Director - Analytical Services
