The detection of perfluoro carboxylic acids in complex environmental matrices utilising ultrasound-assisted extraction and chromatographic analysis

Tuerk, Franziska (2025) The detection of perfluoro carboxylic acids in complex environmental matrices utilising ultrasound-assisted extraction and chromatographic analysis. PhD thesis, University of Glasgow.

Abstract

Anthropogenic chemicals are an essential part of modern life, infiltrating everyday life as well as industrial applications. While those compounds are beneficial in many ways with their intended use, dissemination into the environment has become a significant concern. One class of compounds, per- and polyfluoroalkyl substances (PFASs), have been of particular interest to research, due to their potential adverse effects on non-target species and prolonged residence times in the environment, hence, monitoring of concentration levels is advisable. Wastewater treatment facilities have since been identified as a crucial point source of contamination, recognising that traditional treatment processes are not designed to breakdown complex chemicals and chemical mixtures. By comparison, the practice of sewage sludge (biosolids) application to agricultural land remains less scrutinised despite presenting a more diffuse and unpredictable prospective entry route for contaminants into agriculture and the wider environment, however, readily availability and economic advantage over conventional inorganic fertiliser keeps the application of sludge products relevant.

This thesis describes the method development of a gas chromatographic – mass spectrometric (GC-MS) technique for the detection of perfluoro carboxylic acids (PFCAs) with electron impact ionisation. Optimisation of the methods progressed through the evaluation of instrumental parameters and successfully separated and detected PFCAs (PFHpA (C7) – PFDoA (C12)) with a limit of detection of 25 ng/mL respectively. Efficacy of the method was dependent on the degree of volatility and interaction of compounds with the engaged stationary phase, with smaller PFCAs, ranging from PFBA (C4) to PFHxA (C6), ultimately not successfully retained in the process.

A previously implemented ultrasound-assisted extraction (UAE) method for the detection of pharmaceuticals in biosolids was adapted and optimised for the detection of perfluoro carboxylic acids in biosolids and soil matrices. The amount of soil undergoing extraction was investigated in the process, with 1 gram of soil achieving comparably lower recoveries to 0.5 grams of soil, albeit with improved, reduced relative standard deviations, fitting with the previously optimised to 1 gram of biosolids for the process. The implementation of multiplexing, the simultaneous extraction of three samples, was found to be consistent across the employed sonication device and reduced the sample preparation time by 66 %.

The application of liquid chromatography and orbitrap mass spectrometry (LC-Orbitrap-MS) analysis overcame issues with the detection of smaller PFCAs and overall sensitivity observed GC-MS, however, matrix effects had to be addressed in the process. All investigated PFCAs, ranging from PFBA to PFDoA were detected across six biosolids batches whereas biosolids-amended soils collected over 2 years were found to contain varying levels of predominantly PFHpA and PFDA. Regardless of the continued biannual biosolids application, differences in the PFCA concentration profiles in soil were observed with a spike and successive decrease in concentration within a month of the initial monitored biosolids application. The comparison with agricultural soil that never received biosolids-amendment does not show any significant contamination with PFCAs and hence suggests that the biosolids-amendment is responsible for the introduction of PFCAs into the soil environment receiving the biosolids treatment despite discrepancies in PFCA profiles. The utilisation of UAE and LC-Orbitrap-MS was able to reliably detect PFCA concentrations in both, biosolids and soils, making it a suitable approach for the investigation of environmental trace analysis.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Supported by funding from the University of Glasgow Lord Kelvin and Adam Smith (LKAS) scholarship.
• Subjects: Q Science > QD Chemistry; Q Science > QH Natural history > QH345 Biochemistry
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
• Funder's Name: Lord Kelvin and Adam Smith (LKAS) Scholarship
• Supervisor's Name: Bellingham, Dr. Michelle and Gauchotte-Lindsay, Dr. Caroline
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85120
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 16 May 2025 14:06
• Last Modified: 16 May 2025 14:15
• Thesis DOI: 10.5525/gla.thesis.85120
• URI: https://theses.gla.ac.uk/id/eprint/85120