Graduation Semester and Year
Spring 2026
Language
English
Document Type
Thesis
Degree Name
Master of Science in Chemistry
Department
Chemistry and Biochemistry
First Advisor
Charles Phillip Shelor
Abstract
Poly- and perfluoroalkyl substances (PFAS) are anthropogenic chemicals that have gained increasing attention due to their association with a wide range of adverse health effects. These compounds are highly diverse, with approximately 15,000 PFAS reported. Their exceptional environmental stability and strong tendency to bioaccumulate result in environmentally relevant concentrations that typically occur at very low levels, often in the ng L⁻¹ range. This chemical diversity presents a major analytical challenge, as reference standards are available for only a limited number of PFAS. Consequently, conventional targeted analytical methods frequently quantify less than 1% of the total PFAS present, leading to a significant underestimation of overall PFAS contamination. Combustion Ion chromatography (CIC) has been developed as an alternative approach to overcome these limitations. In this technique, PFAS present in a sample are first retained on activated carbon and then subjected to high-temperature combustion in the presence of argon and water vapor. This process converts organically bound fluorine into hydrogen fluoride (HF), which is subsequently absorbed into a collection solution and quantified using ion chromatography. To simplify analysis, reduce cost and measurement time, this work explores flow-injection based methods for the determination of fluoride as an alternative to conventional ion chromatography. The most straightforward approach employs a fluoride ion-selective electrode (F-ISE). While the F-ISE is capable of detecting fluoride concentrations down iv to approximately 1 µM, its response is logarithmic and the response time varies with concentration, making it better suited for samples containing relatively high fluoride levels. A second flow-injection method is based on fluorescence detection using calcein blue (CB). Calcein blue is highly fluorescent in solution but this decreases upon complexation with Zr-(IV). Upon introduction of fluoride, fluoride ions bind preferentially to Zr-(IV), displacing calcein blue and restoring fluorescence. This fluorescence enhancement serves as the analytical signal for fluoride detection. Compared with ion chromatography, this approach offers faster analysis, simpler instrumentation, reduced susceptibility to interferences, and comparable limits of detection (< 10 nM fluoride).
Keywords
Flow injection analysis, Fluoride determination, Total organic fluorine, PFAS, Fluoride ion-selective electrode, Calcein Blue, Zirconium-Calcein Blue complex, Fluorescence detection, Combustion ion chromatography, Liquid-core waveguide
Disciplines
Analytical Chemistry
License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Recommended Citation
Zulafiqar, Memona, "Flow Injection Determination of Fluoride for Total Organic Fluorine Analysis" (2026). Chemistry & Biochemistry Theses. 4.
https://mavmatrix.uta.edu/chemistry_theses2/4
Comments
I would like to thank my advisor, Dr. Charles Phillip Shelor, for his guidance and support throughout this research. I also sincerely thank my committee members, Dr. Purnendu K. Dasgupta and Dr. Kevin A. Schug, for their time, feedback, and encouragement. I am grateful to the Department of Chemistry and Biochemistry at The University of Texas at Arlington, my lab members, and my family for their support during my graduate studies.