Breakthrough Volumes of Perfluorocarboxylates in Using WAX Cartridges for Analysis of Sewage

Perfluorocarboxylates (PFCAs) are the subject of increasingly intense environmental research due to their persistence, bioaccumulation, toxicity, and global distribution. In order to determine wide chain length PFCAs simultaneously, weak anion exchange (WAX) cartridges have recently been used for solid phase extraction (SPE) in analysis of these chemicals in environmental water samples. However, given the conflicts between the limited ion-exchange capacity of WAX cartridges and the relatively large enrichment coefficient required for analysis of these low pollution level chemicals, it is crucial to select appropriate water sample volumes for specific WAX cartridges in order to ensure the recoveries for all analytes. The objective of this study is to determine the breakthrough volumes of short- and long-chain PFCAs in analysis of sewage using specific WAX cartridges (60 mg, 3 cc) for SPE. The results indicate that the occurrence of breakthrough is dependent on not only the sample volume but also the perfluorocarbon chain length of analytes. The breakthrough volumes for short-chain PFCAs (<C5) range from 200 to 300 mL, while breakthrough does not happen on the medial- (C5-C10) and long-chain ones (>C10) in present study. The relatively low recoveries of long- chain PFCAs (>C10) are mainly due to matrix effects rather than breakthrough because internal standard is not suitable for these chemical. Finally, the volume selected for loading on WAX cartridges (60 mg, 3 cc) in analysis of sewage is 200 mL in order to avoid breakthrough for short-chain PFCAs (<C5) and reduce matrix effect as far as possible for long-chain ones (>C10). Meanwhile, this volume also ensures the quantitation of these chemicals presented in sewage samples because enrichment coefficients are large enough.