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

Abstract

The mass spectral characteristics of perfluorooctane sulfonate (PFOS, C(8)F(17)SO(3)-) isomers present in technical PFOS were obtained using high-resolution gas chromatography (HRGC) combined with mass spectrometry (MS). To make PFOS amenable to HRGC separation, a simple derivatization procedure was developed. The method involved the conversion of PFOS into the iso-propyl ester using iso-propanol as the derivatization reagent under acidic conditions. Mass spectra were generated employing electron ionization (EI) and negative chemical ionization (NCI). Interpretation of fragment ions was possible due to the use of deuterium-labeled iso-propanol as derivatization reagent, which induced mass shifts in the electron ionization (EI) and negative chemical ionization (NCI) mass spectra. HRMS allowed the accurate mass measurement of important EI fragments and confirmed the derivatization reaction as well as the proposed fragmentation pathway involving rearrangement. Moreover, the high resolution provided by HRGC enabled the separation of eleven PFOS isomers present in the technical product. This is an improvement over the previously reported high-performance liquid chromatography (HPLC) separation. A complete identification of all isomers was not possible due to lack of pure reference materials. Finally, the developed derivatization procedure was successfully applied to perfluoroalkyl carboxylates (PFCA) and corresponding fragmentation involving rearrangement of the derivatized PFCA was observed. The described qualitative derivatization offers a promising alternative technique for the separation and identification of isomers of perfluoroalkyl sulfonates and carboxylates by HRGC/MS.

Selected physicochemical aspects of poly- and perfluoroalkylated substances relevant to performance, environment and sustainability—Part one

“…High-resolution gas chromatography coupled with mass spectrometry allowed identification of eleven isomers in a technical PFOS mixture. Inset: magnification (Langlois et al, 2007). 20 tons, for a probably overoptimistic lower emission scenario, to 6420 tons (primarily from fluoropolymer production and fluorotelomer product degradation).…”

“…Products labelled as PFOS typically contain 70-80% of the linear molecule, and up to eleven identified isomers (Fig. 12) (Langlois et al, 2007).…”

Simultaneous qualitative and quantitative analysis of fluoroalkyl sulfonates in riverine water by liquid chromatography coupled with Orbitrap high resolution mass spectrometry

“…Single quadrupole HPLC-MS was another sensitive technique developed for PFSA quantitative analysis, but its selectivity was poor for complex matrixes and is thus invalid for qualitative analysis [16]. A novel method for the characterization of PFOS isomers present in technical products was developed using gas chromatography combined with high resolution mass spectrometry (GC-HRMS), however, an additional 2-propanol derivatization step under acidic conditions was needed to increase the volatility of the polyfluorinated anions [17].…”

Determination of Perfluorinated Compounds in Packaging Materials and Textiles Using Pressurized Liquid Extraction with Gas Chromatography-Mass Spectrometry

“…In order to improve the volatility, sensitivity and performance of the chromatographic response of the two compounds, a previous derivatization step is necessary. 22 Silylation is a suitable procedure for alcohols, phenols and other organic acids, and BSTFA is often used as a derivatization reagent. Figure 1 shows the total ion current spectrum of silylated perfluorinated compounds and the internal standard under the conditions described in Apparatus and software in the SCAN mode.…”