Pan Yitong, Helbling Damian E
School of Civil and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA.
School of Civil and Environmental Engineering, Cornell University, Ithaca, NY 14853, USA.
Water Res. 2023 Oct 1;244:120497. doi: 10.1016/j.watres.2023.120497. Epub 2023 Aug 17.
Per- and polyfluoroalkyl substances (PFASs) are environmental contaminants of concern. Techniques that quantify total organic fluorine (TOF) such as the adsorbable organic fluorine (AOF) and extractable organic fluorine (EOF) methods are important for PFAS risk assessments. The objective of this study was to systematically evaluate each step of the AOF (loading, washing, combustion) and EOF (loading, washing, elution, combustion) methods for the recovery of ten ultrashort-, short-, and long-chain unsubstituted perfluoroalkyl acids (PFAAs). We measured the overall recovery of fluoride for each method for each PFAA, and the recovery of each PFAA around the loading, washing, and elution steps. We also measured the combustion efficiency of each PFAA by direct combustion. The overall AOF and EOF recovery ranged from 9.3%-103.3% to 21.0%-108.1%, respectively, with higher recoveries measured for PFAAs with increasing chain length in both methods. The three ultrashort-chain PFAAs (trifluoroacetic acid, perfluoropropionic acid, and perfluoropropanesulfonic acid) exhibited the lowest overall recoveries from 9.3-25.2% for AOF and 21.0-51.5% for EOF. We found that decreases in the overall recovery are the result of losses of ultrashort- and short-chain PFAAs during the washing step and the incomplete mineralization of perfluoroalkyl sulfonic acids during combustion for AOF and incomplete elution of short- and long-chain PFAAs and the loss of ultrashort-chain PFAAs during the washing step for EOF. Our data suggest that the EOF method is more appropriate than the AOF method for measuring TOF in samples containing ultrashort- and short-chain PFAAs and that methodological improvements are possible with a focus on the washing, elution, and combustion steps.
全氟和多氟烷基物质（PFASs）是备受关注的环境污染物。诸如可吸附有机氟（AOF）和可提取有机氟（EOF）方法等用于量化总有机氟（TOF）的技术，对于PFAS风险评估至关重要。本研究的目的是系统评估AOF方法（加载、洗涤、燃烧）和EOF方法（加载、洗涤、洗脱、燃烧）中回收十种超短链、短链和长链未取代全氟烷基酸（PFAA）的每个步骤。我们测量了每种PFAA的每种方法中氟化物的总体回收率，以及在加载、洗涤和洗脱步骤前后每种PFAA的回收率。我们还通过直接燃烧测量了每种PFAA的燃烧效率。AOF和EOF的总体回收率分别为9.3%-103.3%和21.0%-108.1%，两种方法中随着链长增加，PFAA的回收率更高。三种超短链PFAA（三氟乙酸、全氟丙酸和全氟丙烷磺酸）的总体回收率最低，AOF为9.3%-25.2%，EOF为21.0%-51.5%。我们发现，总体回收率的下降是由于超短链和短链PFAA在洗涤步骤中损失，以及AOF燃烧过程中全氟烷基磺酸不完全矿化，和EOF中短链和长链PFAA洗脱不完全以及超短链PFAA在洗涤步骤中损失所致。我们的数据表明，对于测量含有超短链和短链PFAA的样品中的TOF，EOF方法比AOF方法更合适，并且聚焦于洗涤、洗脱和燃烧步骤有可能改进方法。
