- Title
- Detection and quantification of per- and polyfluoroalkyl substances (PFAS) and precursors from environmental matrices
- Creator
- Al Amin, Md
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2023
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Due to the extraordinary properties that are not expected from other substances, per- and polyfluoroalkyl substances (PFAS) have become widely used compounds in a variety of activities, but potentially dangerous to human health and that of flora and fauna. Unfortunately, while there are approximately 5,000 PFAS compounds on the global market, currently, only 30-80 are known to be quantitatively detected, and the rest are known as “PFAS precursors”. Thus, the detection and quantification of PFAS and their precursors require paramount attention, leading to the refinement of various techniques to analyse PFAS with selectivity, specificity, and sensitivity, which are the aims of this thesis. In chapter 4 (Experiment #1), a fluoro-solid phase extraction (Fluoro-SPE) was applied to selectively extract fluorosurfactants (FS) of PFAS, which consist of fluoro-carbon (C-F) skeletons. In the meantime, other anionic surfactants that usually co-exist with FS but do not contain any fluoro-carbon (non-C-F) skeletons can be differentiated from FS by Fluoro-SPE due to the fluoro chemistry. To increase detection sensitivity, styrene-divinylbenzene polymer resin-solid phase extraction (SDVB-SPE) served to concentrate the target sample, for instance, from 500 mL to 5 mL (~100). Consequently, the detection limit of PFAS such as perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS) and 1H, 1H, 2H, 2H-perfluorooctanesulfonic acid (6:2 FTS) has reached ~1 ppb (part per billion, or g/L), which is promising and can be done in a general laboratory. Chapter 5 (Experiment #2) investigated the mechanism of the total oxidisable precursors (TOP) assay, to check the bond stability of the C-F and the non-C-F in PFAS and their precursors. The TOP assay is able to degrade non-C-F-containing compounds such as sodium dodecyl benzene sulphate (SDBS), and the non-C-F groups in PFAS precursors. However, it could not degrade C-F-containing compounds like PFOA and PFOS. To detect the different types of intermediates or end products, the TOP assay was applied to several “known PFAS” precursors as models, such as 6:2 and 1H, 1H, 2H, 2H-perfluorodecanesulfonic acid (8:2 FTS), and N-ethyl-N-(2- hydroxyethyl) perfluorooctyl sulfonamide (EtFOSE). Finally, the TOP assay was validated to discover the “unknown PFAS” in aqueous film-forming foam (AFFF). Following the above experiment, the TOP assay was further modified and optimised in chapter 6 (Experiment #3) to improve the oxidation and degradation efficiency, particularly for complex samples such as AFFF and soil. The method was applied to different AFFF, with three different dilution times to check the effect of the initial concentration. Proper oxidation can be achieved by changing the initial concentration of the target samples, by: firstly, increasing the doses of the oxidising reagents; and secondly, prolonging the duration and increasing temperature. The optimised TOP assay was finally validated by testing the PFAS-contaminated soil samples. In chapter 7 (Experiment #4), as an alternative to the above TOP assay that was conducted in alkaline conditions (NaOH + K2S2O8, for 6-8 hours), an acidic treatment with acidic oxidising agents, namely sulphuric acid (H2SO4) and hydrogen peroxide (H2O2), was examined. PFOA, PFOS and 6:2 FTS were selected as model compounds to evaluate the extent of degradation and oxidation with different ratios of H2SO4: H2O2 (v/v) in “piranha solutions”. It was noted that the degradation of the C-F and non-C-F bonds of PFAS compounds occurred quickly (~0.5 hours). In other words, the tested compounds were degraded successfully, although it was evident that selectivity needs improvement. As another alternative to the solution or liquid treatments above, chapter 8 (Experiment #5) explored a thermal treatment of the PFAS-contaminated soil for the selective detection and conversion of PFAS and their precursors. Herein, different temperatures and times were applied to study the thermal degradation of PFAS in the soil samples. Temperatures and time intervals for effective PFAS degradation were found to rely on the PFAS compounds. While liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) is typically applied to detect the individual PFAS specifically, the app-based smartphone sensor can provide a semi-quantitative result of PFAS as a sum, such as for pre-screening. The detection selectivity, sensitivity, and specificity of PFAS and their precursors in diverse environmental matrices were studied by introducing Fluoro-SPE and SDVB-SPE, along with the modified TOP assays and newly developed acidic and thermal treatments. The findings presented in this thesis could potentially be used by researchers, agencies or bureaucracies in charge of regulating PFAS and environmental protection organisations.
- Subject
- polyfluoroalkyl substances (PFAS); per- and polyfluoroalkyl substances (PFAS); environmental; matrices
- Identifier
- http://hdl.handle.net/1959.13/1504789
- Identifier
- uon:55574
- Rights
- Copyright 2023 Md Al Amin
- Language
- eng
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 13 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 266 KB | Adobe Acrobat PDF | View Details Download |