A novel methodology for the determination of neutral perfluoroalkyl and polyfluoroalkyl substances in water by gas chromatography-atmospheric pressure photoionisation-high resolution mass spectrometry

J F Ayala-Cabrera; A Contreras-Llin; E Moyano; F J Santos

doi:10.1016/j.aca.2019.12.004

A novel methodology for the determination of neutral perfluoroalkyl and polyfluoroalkyl substances in water by gas chromatography-atmospheric pressure photoionisation-high resolution mass spectrometry

Anal Chim Acta. 2020 Mar 1:1100:97-106. doi: 10.1016/j.aca.2019.12.004. Epub 2019 Dec 3.

Authors

J F Ayala-Cabrera¹, A Contreras-Llin¹, E Moyano², F J Santos³

Affiliations

¹ Department of Chemical Engineering and Analytical Chemistry, University of Barcelona, Av. Diagonal 645, E‒08028, Barcelona, Spain.
² Department of Chemical Engineering and Analytical Chemistry, University of Barcelona, Av. Diagonal 645, E‒08028, Barcelona, Spain; Water Research Institute (IdRA), University of Barcelona, Montalegre 6, E‒08001, Barcelona, Spain.
³ Department of Chemical Engineering and Analytical Chemistry, University of Barcelona, Av. Diagonal 645, E‒08028, Barcelona, Spain; Water Research Institute (IdRA), University of Barcelona, Montalegre 6, E‒08001, Barcelona, Spain. Electronic address: javier.santos@ub.edu.

PMID: 31987157
DOI: 10.1016/j.aca.2019.12.004

Abstract

Here, we developed and validated a new gas chromatography-atmospheric pressure photoionisation-high-resolution mass spectrometry (GC-APPI-HRMS) method combined with headspace solid-phase microextraction (HS-SPME) for the determination of neutral perfluoroalkyl and polyfluoroalkyl substances (PFASs) in water samples. The method includes fluorotelomer olefins (FTOs), fluorotelomer alcohols (FTOHs), fluoroctanesulfonamides (FOSAs) and sulfonamido-ethanols (FOSEs). The feasibility of the GC-APPI interface for the ionisation of the target compounds was evaluated, achieving the best results using negative-ion dopant-assisted ionisation with acetone and a source and capillary temperatures of 225 °C and 175 °C, respectively. Under optimal conditions, FTOs and FTOHs mass spectra showed intense in-source CID fragment ions from the fluoroalkyl chain but also the superoxide [M+O₂]^-• adduct ion. For FOSAs, [M-H]^- was the main ion generated, while FOSEs mass spectra showed fragment ions corresponding to the different cleavages of the functional group. The high ionisation efficiency achieved with the GC-APPI interface provided limits of the detection lower than those obtained using traditional GC-MS ionisation techniques, with a high sensitivity, selectivity and precision. For water analysis, a fast and simple HS-SPME procedure was developed, avoiding evaporation steps, which could lead to the loss of the most volatile compounds. The developed HS-SPME GC-APPI-HRMS method showed a good analytical performance for the analysis of river water samples, providing very low limits of detection (0.02-15 ng L^-1), good repeatability (RSD < 11%) and trueness (relative error < 12%).

Keywords: Atmospheric pressure photoionisation; Gas chromatography; Headspace-solid-phase microextraction; High resolution mass spectrometry; Neutral per- and polyfluoroalkyl substances.