Topic: While long-chain per- and polyfluorinated alkyl substances (PFAS) are found globally in waterways due to their solubility, short-chain PFAS are widely encountered in, and transported through, the atmosphere. Our attention should be focused on the sources where volatile PFAS are emitted: Much closer to home in our indoor spaces. GERSTEL application experts have now developed an efficient, economical, and sustainable method based on thermal desorption and GC-MS/MS, with which fluorotelomer alcohols (FTOHs) can be safely and sensitively determined and quantified in air. 

The Challenge: PFAS belong to a group of synthetic organic chemicals that are widely used in industry as well as by consumers because of their physicochemical properties. PFAS repel water, oil, grease, and dirt and they are soluble in water, extremely heat-resistant and chemically stable. PFAS are also persistent, ubiquitous, and hazardous to health. The PFAS relevant to environmental and food analysis can be roughly divided into two groups of substances: perfluorinated alkyl sulfonates (PFAS), with perfluorooctane sulfonate (PFOS) as the best-known representative, and perfluorinated carboxylic acids (PFCA), the best-known representative of which is perfluorooctanoic acid (PFOA). The PFAS fluorotelomer alcohols (FTOHs), among others, are broken down into PFOA. FTOHs [CF3(CF2)nCH2CH2OH] give textiles, carpets and building materials water- and grease-repellent properties. FTOHs are highly volatile and are nearly always found in indoor air due to material emissions. According to the Federal Environment Agency, young people are particularly exposed to high FTOH levels. 

Solution: Indoor PFAS emissions should be kept to a minimum. Supposedly non-critical emissions can accumulate to reach alarming levels over time and therefore FTOH pollution in indoor air must be monitored. Jackie A. Whitecavage, Kurt Thaxton and Robert Collins from GERSTEL have recently developed and evaluated a method for the determination of FTOHs in air based on the use of solvent-free thermal desorption coupled to gas chromatography and tandem mass spectrometry (TD-GC-MS/ MS). The method allows the determination of PFAS/FTOH contamination in air and the identification of potential emission sources in accordance with the requirements of the US Environmental Protection Agency (US EPA). 

Technique: Whitecavage and colleagues use the following instrument combination to determine the FTOHs (4:2 FTOH, 6:2 FTOH, 8:2 FTOH and 10:2 FTOH), which are increasingly targeted by the US EPA: TD Core System (thermal desorber based on a TD 3.5+) combined with an 8890 GC and 7000E GC Triple Quadrupole MS (both from Agilent Technologies). The GC was equipped with a GERSTEL Cooled Injection System (CIS 4). For sampling, the application experts use thermal desorption tubes designed for low flow rates and filled with Tenax TA; active sampling was performed using a pump (SKC). 

Analysis: First, 3 µL of the calibration standard and the internal standard (10:2 FTOH [M+4]) were injected to conditioned TD tubes using a 10 µL syringe and the solvent from the sorbent bed purged with nitrogen (40 mL/min) for three minutes. For sampling, the spiked TD (3.5+) tubes were connected to a three-way adjustable low-flow tube holder and a sampling pump (SKC Pocket Pump Touch). As Whitecavage and her colleagues report, the sampled analytes were desorbed in the TD Core System (GERSTEL) in splitless mode with a helium flow of 50 mL/min at 300 °C for 3 minutes and the analytes focused on a Tenax TA packed liner in the CIS 4 at 10 °C. Desorption and transfer of the analytes to the separation column were performed in split mode (10:1) by programmed heating at 12 °C/s to 280 °C (3 min). 

Results: Whitecavage et al. collected air samples from several locations in an office building and in a private household for further analysis. Sampling was performed over a 24 hour period at an air sampling rate of 40 mL/min. The samples were analyzed for FTOH contamination. TD-GC-MS/MS analysis using MRM mode (Multiple Reaction Monitoring) provides outstanding selectivity enabling the determination of trace level FTOH concentrations in complex high matrix load air samples. As Whitecavage and colleagues report: “FTOH 6:2 was detected at all sites sampled. The vapor concentration ranged from 3.47 to 16.5 ng/m3. FTOH 10:2 was detected at four of six locations with a vapor concentration of 3.58 to 16.7 ng/m3." Although the determined concentrations can be described as low, the presence of at least one FTOH in every sample is significant and shows that further investigation is needed. 

Conclusion: Considering that PFAS accumulate in human tissue, long-term exposure, even to supposedly non-critical concentrations, can lead to accumulation of potentially harmful amounts. The TD-GC-MS/MS method developed and evaluated by GERSTEL scientists makes it possible to determine low levels of PFAS in indoor air in an efficient, economical, and sustainable manner, thereby contributing to a healthier indoor environment. 

Reference 

Whitecavage JA, Thaxton K, Collins R. Determination of Fluorotelomer Alcohols in Indoor Air using Cryogen-free Thermal Desorption GC-MS/MS. GERSTEL AppNote 262.