Chromatographic and mass spectral studies of perfluorooctanesulfonate and three perfluorooctanesulfonamides

Abstract

The chromatographic and mass spectral characteristics of perfluorooctanesulfonate (PFOS) and three nitrogen-substituted perfluorooctanesulfonamides have been obtained. A methyl/phenyl mixed-phase fused-silica capillary column was used for gas chromatographic (GC) analyses, while a C18 reversed-phase microbore column was used for liquid chromatographic (LC) analyses. Mass (MS) and tandem mass (MS/MS) spectra were generated using electron ionization (EI), argon CE, methane positive and negative ion CI, and ES ionization modes. EI spectra of the amides showed ions characteristic of both the fluorinated hydrocarbon and the sulfonamide portion of the molecules. The fragmentation pathway was studied using hydrogen/deuterium exchange, and was thought to involve a cyclic intermediate ion. Formation of molecular ions by CE and protonated molecule ions by CI to obtain molecular weight information was only partially successful. Negative ion ES-MS spectra provided intense [M-H] À anions for the amides, and an [M-K] À anion for PFOS from which molecular weight information could be obtained, while ES-MS/MS produced product ions that could be used to detect the presence of these compounds in biological or environmental samples. Published in

Mass spectral studies of perfluorooctane sulfonate derivatives separated by high‐resolution gas chromatography

“…The loss of the methyl group from the deriv‐PFOS molecular ion at m/z 542 gave the fragment ion at m/z 527 followed by a loss of SO 2 forming the ion at m/z 463 [M–CH 3 –SO 2 ] + . A similar loss of SO 2 has been reported for some perfluoroalkyl sulfonamides in the EI mode 20. Moreover, HSO 2 was cleaved off from the molecular ion leading to m/z 477.…”

“…However, the [M−H] + ion of derivatized PFHS ( m/z 441) was detected in the EI‐HR mass spectra (see later). Two typical PFAS fragmentation series occurred 20. One series started at m/z 69 [CF 3 ] + (‘9‐series’) and a second series at m/z 131 [C 3 F 5 ] + (‘1‐series’).…”

Mass spectral studies of native and mass‐labeled perfluorooctanesulfonamides

“…1(a) and the fragment ions identified are summarized in Table 1. As indicated in the earlier work,27 the molecular ion ( m/z 499) is not detected (a weak ion, at m/z 500, corresponding to [M+H] + , can be seen in Fig. 1(a)).…”

“…Arising from the former moiety, we find ions resulting from further fragmentation that are assignable to the three series; C n F 2n + 1 (n = 1, 2 … 6; m/z 69, 199, … 319), C n F 2n − 1 (n = 3, 4 … 8; m/z 131, 181…381), and C n F 2n‐3 (n = 3, 4 … 8; m/z 93, 143 … 343). The latter series is of relatively low intensity signal compared with the other two, and was not previously reported 27. One further, related, fragment ion, at m/z 100, corresponds to [C 2 F 4 ] .…”

“…A study of the mass spectral behaviour of FOSA and of NEtFOSA has been reported 27. In this publication, possible pathways for the formation of some of the fragment ions were proposed but gaps in the fragmentation scheme still remain.…”