Citation:

Miller, K. AND M. Strynar. A Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Method to Improve Detection of Low Molecular Weight Perfluoroalkyl Ether Carboxylic Acid (PFECA) Isomers. 2021 SETAC North America Annual Meeting, Virtual, November 14 - 18, 2021.

Impact/Purpose:

This study aims to improve liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection of per- and polyfluoroalkyl substances (PFAS) isomers, specifically from the class perfluoroalkyl ether carboxylic acids (PFECA). Current literature and methods often do not monitor for these isomers, which results in underestimated PFAS values. This work develops an LC-MS/MS method that determines which mass transitions provide the highest signal and how these mass transitions are affected across different matrices like drinking water, serum, and fish liver. These findings will be of interest to PFAS researchers and risk assessors. 

Description:

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants widely used in a variety of industrial and consumer applications (e.g., fire-fighting foams, household products, etc.). These anthropogenic chemicals persist in various environmental media including water, soil, and air. Due to phasing out legacy PFAS, some manufacturers developed short-chain alternatives like perfluoroalkyl ether carboxylic acids (PFECA), which contain ether bond(s) in the perfluorinated carbon backbone. Published liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods cover a wide range of these replacement chemicals including perfluoro-3-methoxypropanoic acid (PFMPA) and perfluoro-4-methoxybutanoic acid (PFMBA). However, many methods do not monitor for the branched isomers of PFMPA and PFMBA, which are perfluoro-2-(perfluoromethoxy)propanoic acid (PMPA) and perfluoro-2-ethoxypropanoic acid (PEPA), respectively. Although these isomers are chromatographically separable under certain conditions, using the common MS/MS transitions for PFMPA (m/z 229 → 85) and PFMBA (m/z 279 → 85) will yield low or no detection signal for PMPA and PEPA, thus leading to underestimated values or non-detects. Herein, we developed an LC-MS/MS method that compared various MS/MS transitions for these isomers. We applied the developed method to different matrices including drinking water, serum, and fish liver. Current observations demonstrated that the highest signal is received when using the following mass transitions: PMPA (m/z 185 → 85) and PEPA (m/z 235 → 135). These MS/MS transitions will improve detection of these isomers and lead to better monitoring and exposure estimates of PFECA in humans and the environment.

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