Shields, Erin
(2019)
Liquid Chromatography Stationary Phases Made Using the Thiol-yne Reaction.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Stationary phases for HPLC that can withstand extremes of pH and temperature are needed to allow a single column to accommodate a wider set of solutes and separation criteria. This work investigates the use of the click chemistry thiol-yne reaction to create unique stationary phases that are stable at extreme pHs. Stationary phases were made by adding either 1,4-diethynylbenzene (DEB) or 1,7-octadiyne to propylthiol modified silica particles. The diynes were then crosslinked using 1,6-hexanedithiol. The main difference between the two types of phases was the presence of the benzene ring with the DEB modifier particles. Both phases show high stability in a 50:50 pH 0.5 5% TFA:acetonitrile mobile phase at 70 C. With the retention of triphenylene dropping 10% for the DEB based phase and 20% for the octadiyne phase. It was found that all the thiol-yne and thiol based stationary phases have a nitrobenzene to benzene selectivity factor greater than 1, indicating the phases possess electron donating charge-transfer characteristics due to the presence of the sulfur atom. The DEB phase’s electron-donating characteristic is enhanced by a conjugated pi system between the sulfur and benzene ring. The DEB based phase also has an enhanced Tanaka test shape selectivity factor, between the flat triphenylene and bulky o-terphenyl molecules, of 4.91 ± 0.08, which is higher than almost all other reversed-phase stationary phases. The octadiyne phase’s shape selectivity was 2.71 ± 0.03, still high, but much lower than with the DEB moiety in the phase. Cation-exchange characteristics were apparent in both phases, indicated by the Tanaka test. The DEB based phase had a benzylamine and phenol selectivity factor of around 22, while the octadiyne phase’s was almost 4 at pH 2.7. With the methylene selectivities around 1.2 for all the phases, in the range of a typical C18 column, it is apparent that the thiol-yne phases are mixed-mode stationary phases. The octadiyne phase was used to separate monoamine neurotransmitters showing the phase’s hydrophobic and cation-exchange nature. These stable phases can provide a complementary phase to reversed-phase stationary phases and can be useful in many different fields.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
25 September 2019 |
| Date Type: |
Publication |
| Defense Date: |
19 August 2019 |
| Approval Date: |
25 September 2019 |
| Submission Date: |
20 August 2019 |
| Access Restriction: |
1 year -- Restrict access to University of Pittsburgh for a period of 1 year. |
| Number of Pages: |
136 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Thiol-yne; stationary phase; mixed-mode; charge-transfer |
| Date Deposited: |
25 Sep 2019 16:45 |
| Last Modified: |
25 Sep 2020 05:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/37395 |
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