Analysis of fluorotelomer alcohols and perfluorinated sulfonamides in biotic samples by liquid chromatography-atmospheric pressure photoionization mass spectrometry

doi:10.1016/j.chroma.2008.10.103

Journal of Chromatography A

Volume 1215, Issues 1–2, 26 December 2008, Pages 92-99

https://doi.org/10.1016/j.chroma.2008.10.103 Get rights and content

Abstract

A quantitative analytical method was developed to simultaneously detect fluorotelomer alcohols (6:2 FTOH, 8:2 FTOH and 10:2 FTOH) and polyfluorinated sulfonamides (perfluoro-1-octanesulfonamide (FOSA) and N-methylperfluoro-1-octanesulfonamide (NMeFOSA)) in biotic samples with liquid chromatography-atmospheric pressure photoionization mass spectrometry (LC-APPI-MS/MS). APPI mass spectra for FOSA and NMeFOSA showed that the major ionization mechanism was not photoionization, whereas for the FTOHs it was photoionization. For FTOHs, a [M+O₂]⁻ ion was generated with a similar response as the deprotonated molecular ion [M−H]⁻. We demonstrated that FTOHs, FOSA and NMeFOSA can be measured in various biota samples using APPI with a minimized matrix effect. Using APPI, the linear response range for the FTOHs was 0–1000 ng/mL (r² > 0.9997), and for FOSA and NMeFOSA ranged from 0 to 250 ng/mL (r² > 0.995). The instrument and method detect limits ranged from 0.16 to 0.63 pg and below 1 ng/g wet weight (w.w.), respectively. For the overall method applied to the test matrices, recovery efficiencies ranged from 73 to 102% for egg homogenate and 89–100% for liver tissue. The present study demonstrates for the first time that a far more response and sensitive approach for the detection and quantification of FTOHs and polyfluorinated sulfonamides is possible using APPI as opposed to electrospray ionization.

Introduction

Several types of polyfluoroalkyl and perfluoroalkyl compounds (PFCs) have been found to be globally distributed anthropogenic contaminants [1], [2], [3], [4], [5], [6], [7]. Although the sources of the many persistent PFCs found in the environment are not entirely clear and recent studies have revealed that levels of PFC contamination, mainly perfluorinated sulfonates (PFSAs) and perfluorinated carboxylates (PFCAs), have shown an increasing trend during the last decades [1], [2], [3], [4], [5], [6], [7], [8], [9]. Fluorotelomer alcohols (FTOHs) and perfluorinated sulfonamides have been suggested as precursors of PFSAs and PFCAs in the environment [7], [10], [11] It has been hypothesized that the volatile FTOHs and perfluorinated sulfonamides released as residuals during product processing, transported atmospherically and subsequently degraded to form the persistent PFCA and PFSA as their terminal products [3], [5], [7], [10], [11], [12]. Therefore, measuring the contamination level of FTOHs and perfluorinated sulfonamides in different environmental matrices is important, as this may demonstrate the relationship between their sources and their terminal product contamination.

At present most of the analysis methods for PFCs in environmental samples have focused on PFCAs and PFSAs, and much less attention has been on the perfluorinated sulfonamides and FTOHs [13], [14]. Reports on the measurement of FTOHs and perfluorinated sulfonamides in biological samples are exceedingly rare, though they have been shown to be in air, water, tissue and/or plasma samples [7], [8], [11], [14], [15], [16], [17], [18]. In contrast to PFCAs and PFSAs the determination of FTOHs and perfluorinated sulfonamides in biological samples is more challenging. Conventionally, the majority of analyses for the semi-volatile FTOHs and perfluorinated sulfonamides has been done by GC/MS methods [3], [7], [8], [12], [15], [18], [19]. However, GC/MS methods have shown poor sensitivity and necessitate a complex sample cleanup. A method based on liquid chromatography-tandem quadrupole mass spectrometry with electrospray ionization (LC-ESI-MS/MS) was also used for determination of FTOHs and perfluorinated sulfonamides [20]. However, ESI was shown to be subject to greater ionization suppression and matrix effects [21], [22].

Atmospheric pressure photoionization (APPI) is a relatively new LC-coupled ionization source [23], [24], [25]. APPI source has demonstrated efficient ionization of nonpolar or low charge affinity compounds, a lower sensitivity to matrix effects, and a large linear dynamic range of response, but its application has received minimal attention in PFC analysis [26]. To our knowledge there are no literature reports on the use of LC-APPI-MS(/MS)-based methodology for the determination of FTOHs and perfluorinated sulfonamides for any standard solution or in any environmental matrix. In the present study, we developed a robust, reliable and sensitive analytical method based on solid-phase extraction with weak anion-exchange (WAX) cartridges and the determination of target compounds by LC-APPI-MS/MS. The target compounds under study are 6:2 FTOH, 8:2 FTOH and 10:2 FTOH, and perfluorooctane sulfonamide (FOSA) and NMeFOSA.

Section snippets

Chemicals

The standards of target analytes included three FTOHs (2-perfluorohexyl ethanol, CF₃(CF₂)₅CH₂CH₂OH (6:2 FTOH); 2-perfluorooctyl ethanol, CF₃(CF₂)₇CH₂CH₂OH (8:2 FTOH), 2-perfluorodecyl ethanol, CF₃(CF₂)₉CH₂CH₂OH (10:2 FTOH)) and two perfluorinated sulfonamides (perfluoro-1-octanesulfonamide,CF₃(CF₂)₆CF₂SO₂NH₂ (FOSA) and N-methylperfluoro-1-octanesulfonamide CF₃(CF₂)₆CF₂SO₂NHCH₃ (NMeFOSA)) were purchased from Wellington Labs. (Guelph, Canada). Three isotopically-labeled FTOHs,

Sample extraction and clean up

Although there are numerous published reports on the monitoring of PFCs in environmental samples, the extraction (and clean up) processes are mainly based on two analytical approaches. One is ion-pairing extraction (IPE) of ionic PFCs and the other is based on SPE [15], [16], [18], [31]. Theoretically, IPE methods can be used to co-extract neutral and other PFCs, such as FTOHs and perfluorinated sulfonamides. However, published IPE-based extraction methods did not include further sample cleanup

Conclusions

It has been demonstrated that a LC-APPI(−)-MS/MS-based analytical method is essential for optimal determination of FTOHs and perfluorinated sulfonamides in complex biological samples. This optimal and reliable quantitative method shows superior sensitivity and less matrix effects relative to other approaches, e.g., using ESI. It is likely that this method could be easily adopted for the determination of these neutral PFCs in other matrices such as water and air, where FTOHs are likely at higher

Acknowledgment

Funding support for this study was from the Environment Canada's Chemical Management Plan and Wildlife Toxicology and Disease Program (to R.J.L.), and also from the a Discovery Grant from the Natural Science and Engineering Research Council (NSERC) of Canada (to R.J.L.). We thank Catherine Corrigan (NWRC) for her expert technical contribution in the development of this methodology. We thank all involved people and communities in the collection and provision of polar bear and bird eggs from high

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Analysis of fluorotelomer alcohols and perfluorinated sulfonamides in biotic samples by liquid chromatography-atmospheric pressure photoionization mass spectrometry

Abstract

Introduction

Section snippets

Chemicals

Sample extraction and clean up

Conclusions

Acknowledgment

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