Structural identification of isomers present in technical perfluorooctane sulfonate by tandem mass spectrometry
Ingrid Langlois1, Michael Oehme
1The University of Basel, Organic and Analytical Chemistry Institut, Neuhaustrasse 31, Basel 4057, Switzerland.
Abstract:
The structures of isomeric by-products of technical perfluorooctane sulfonate (PFOS, C8F17SO3-) were characterized by high-performance liquid chromatography coupled to mass spectrometry. Ion trap (IT) as well as triple quadrupole (TQ) tandem mass spectrometry (MS/MS) identified ten PFOS isomers with best results being achieved by ion trap MS/MS. In addition to the linear isomer, the main by-products were isomers with geminal diperfluoromethyl groups and perfluoromethyl-substituted compounds. Purified fractions of the perfluoromethyl isomers allowed the elucidation of structures and the assignment of the retention times of perfluoroisopropyl-, 5-perfluoromethyl-, 4-perfluoromethyl-, 3-perfluoromethyl- and 1-perfluoromethyl-PFOS. The concentration of 2-perfluoromethyl-PFOS was too low in technical PFOS for a proper identification. Retention times of the geminal substituted diperfluoromethyl isomers could not be properly assigned due to co-elutions. The number and position of the CF3 groups can be derived from the MS/MS spectra, which allow an unequivocal identification of the isomers. TQ-MS/MS also allowed us to identify most of the isomers.
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