In a recent paper authored by Jana H.Johansson et al, published in the journal Emerging Contaminants ((2017) 3 46-53)), UCT’s world famous Clean Up® QAX sorbent was employed in a study involving the analysis of PFOS, especially water-to-air transfer of branched and linear perfluorooctanoic acids (PFOA).UCT is known around the world for the production of the finest sorbents for environmental type extractions and PFOS are now gaining recognition as compounds of environmental interest. In this study, the volatilization of perfluorooctanoic acid (PFOA) was measured experimentally at a range of pH values using a validated laboratory method published by the authors. The water-to-air transfer was studied for five structural isomers, namely: the linear isomer (n-PFOA) and the four most commonly occurring branched isomers (3-, 4-, 5- and 6-PFOA). The influence of water concentration and water type on the pH-dependent water-to-air transfer was also investigated for n-PFOA. The water-to-air transfer was studied over the course of 48 hrs at pH values ranging from 0.2 to 5.5.
Under all experimental conditions tested, the volatilization of PFOA was negligible at pH > 2.5. In experiments performed with high purity laboratory water, extractions were performed using CUQAX256 (500mg/6mL). It was found that volatilization increased with decreasing water pH. In experiments performed with tap water and lake water, maximum volatilization was observed at pH 1. The concentration of PFOA in water had no influence on the pH value at which water-to-air transfer was observed (i.e. at pH < 2.5) for the concentration range tested (0.1–50 μg/L PFOA in deionized water). Although the percentage of volatilized PFOA was significantly different for the four branched isomers at low pH, volatilization was not observed above pH 2.5 for any branched isomer suggesting that all PFOA isomers have a low pKa.
Overall, these laboratory results demonstrate that volatilization of any structural isomer of PFOA from water is negligible at environmentally-relevant conditions. For more information regarding Clean Up ® sorbents, methods and applications please visit: https://sampleprep.unitedchem.com/products/spe/environmental/enviro-clean-spe-tubes/enviro-clean-anion.