Graduation Semester and Year
Spring 2025
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Chemistry
Department
Chemistry and Biochemistry
First Advisor
Purnendu K. Dasgupta
Abstract
ABSTRACT
FUNCTIONALIZATION AND USE OF POLYOLEFIN CAPILLARIES IN ION CHROMATOGRAPHY
Ion chromatography (IC), in particular suppressed ion chromatography, is a benchmark tool for ion analysis today. This is especially true for anion analysis, where few alternatives exist. Open tubular liquid chromatography has been known for more than 40 years, but successful practical implementation has been very difficult. Thus, the initial motivation to pursue this project to overcome these difficulties.
This dissertation focuses on the most important component of any chromatography system, the column. Specifically, it focuses on open tubular (OT) columns, which, when fabricated with small inner diameters (i.d.), offer exceptional efficiency. The fitting and connections within an IC system become increasingly critical as the inner diameter (i.d.) of the open tubular columns (OTC) decreases. The smallest commercially available fitting is designed for tubes with a 360 µm o.d.. The performance of OTCs improves without limit as one goes down in i.d.. However, injection, detection, and connection all become exponentially more difficult. We find an acceptable compromise is reached between 10-30 µm inner bore. or a nominal inner diameter of 20 µm.
The only capillary tube that is reliably available in desired outer and inner diameters is made of fused silica. Unfortunately, for hydroxide eluent chromatography, silica is not an acceptable choice because over time the silica dissolves and even during the time it can be used; suppressed background is slightly higher than desired because of the presence of dissolved silicate. Polymeric capillaries are not available in these dimensions. The only capillary that became commercially available during this work is PEEK. It nominally has a bore of 25 µm but is often the inner diameter is high as 38 µm. we worked with a manufacture who was able to reliably extrude polymeric capillaries in desired dimension, however they only work with high- density polyethylene (HDPE) and polypropylene (PP). Polyolefin plastics are best knowns of their inertness and are not easy to functionalize. While PP maybe easier to functionalize than HDPE because of the side chains, HDPE is preferred because it is a linear polymer and hence more rigid.
The primary goal in this research is to utilize HDPE capillaries (20 µm i.d., 350 µm o.d.) as OTCs to perform open tubular ion chromatography (OTIC). The dissertation focuses on the precise determination of the inner and outer diameters of the capillaries assessing the geometric quality of the polymer capillary tubes through circularity and concentricity measurements and functionalizing the polymer capillaries for use as OTCs. Additionally, this work covers OTC capacity measurements, evaluation of radiation stability of anion exchange OTC’s, and the development of a suppressor made from the same HDPE capillary.
Keywords
Ion Chromatography, Ion exchange capacity, high- density polyethylene, Open tubular ion chromatography, Open tubular columns, Surface functionalization, circularity, concentricity, polyolefin surface modification
Disciplines
Analytical Chemistry | Environmental Chemistry | Other Chemistry | Polymer Chemistry
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Yousef, Enas, "FUNCTIONALIZATION AND USE OF POLYOLEFIN CAPILLARIES IN ION CHROMATOGRAPHY" (2025). Chemistry & Biochemistry Dissertations. 283.
https://mavmatrix.uta.edu/chemistry_dissertations/283
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