Date of Award
1-1-2024
Document Type
Dissertation
Degree Name
Ph.D. in Chemistry
First Advisor
James V. Cizdziel
Second Advisor
Ryan Fortenberry
Third Advisor
Murrell Godfrey
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
The research detailed in this dissertation centers on the development of new analytical methods using chemical imaging microspectroscopy, primarily μ[micro]-FTIR, for applications in environmental, forensic, and archeological chemistry. The state-of-the-art instrument (LUMOS II) used in this research combines optical microscopy with IR spectroscopy, allowing sample visualization during FTIR imaging and micro-analysis.
Chapter 1 serves as an introduction and provides background detail on the instrumentation and technique. Chapter 2 describes the use of fluorescent microscopy to quantify microplastics (MPs) in oysters from the Mississippi Sound. High concentrations of putative MPs were found, with sites inside bays near population centers displaying higher levels than those exposed to the Gulf. Chapter 3 expands this work by using μ-FTIR to characterize the MPs found in these oysters in terms of polymer composition, morphology, and size. Average MP concentrations were lower in samples analyzed with μ-FTIR than with fluorescence, and each site and dissected tissue showed variable MP concentrations and characteristics. Chapter 4 focuses on the use of μ-FTIR point measurements to rapidly characterize MP pollution in the Mississippi River System during flash drought conditions. Polymer composition, though not concentration, was found to vary between samples collected during drought and non-drought conditions, and fluoropolymers were highly correlated with flash drought conditions. Chapter 5 explores the use of Optical Photothermal Infrared Spectroscopy (O-PTIR) and compares it with FTIR microscopy for the forensic analysis of thin primer layers in automobile paint systems. O-PTIR’s concurrent IR and Raman measurements show the technique’s promise, though it is not currently part of forensic standards. Results also showed that point measurements with a liquid nitrogen cooled MCT detector along with a knife edge aperture produced the best quality spectra, confirming μ-FTIR’s validity for samples close to the technique’s resolution limit. Chapter 6 details FTIR imaging for the investigation of organic binders used in prehistoric rock art. Although a few spectra were collected with peaks that suggest a proteinaceous binder, the binder’s IR signal was overwhelmed by the embedding resin in the majority of samples, showing that samples must be analyzed via μ-FTIR analysis prior to preparation for stereomicroscopy and SEM.
Recommended Citation
Witharana, Sapumal Asiri, "FTIR Microspectroscopy for the Investigation of Microplastic Pollution, Automotive Paint Layers, and Prehistoric Rock Paint with an Emphasis on Analytical Method Development" (2024). Electronic Theses and Dissertations. 2987.
https://egrove.olemiss.edu/etd/2987