Voltammetric studies on vitamin E in organic solvents and within lipid bilayer membranes
A series of model tocopherol compounds with differing degrees of methyl substitution around the aromatic ring were studied by variable scan rate (0.1- 500 V s-1) cyclic voltammetry experiments in CH3CN and CH2Cl2. On short voltammetric timescales α-TOH is oxidised in a chemically reversible –2e–/–H+...
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| Format: | Thesis |
| Language: | English |
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2011
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| Online Access: | https://hdl.handle.net/10356/44564 |
| _version_ | 1826112223547752448 |
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| author | Yao, Wei Wei |
| author2 | Richard David Webster |
| author_facet | Richard David Webster Yao, Wei Wei |
| author_sort | Yao, Wei Wei |
| collection | NTU |
| description | A series of model tocopherol compounds with differing degrees of methyl substitution around the aromatic ring were studied by variable scan rate (0.1- 500 V s-1) cyclic voltammetry experiments in CH3CN and CH2Cl2. On short voltammetric timescales α-TOH is oxidised in a chemically reversible –2e–/–H+ process to form a phenoxonium cation (α-TO+). The equilibrium and rate constants associated with the chemical steps were estimated by digital simulations of the variable scan rate data over a range of temperatures (T = 253-313K).
α-Tocopherol films were deposited on the surface of gold, glassy carbon and platinum electrodes and their voltammetric behavior examined in aqueous solutions between pH 3 and 13. The voltammetric mechanism involved α-tocopherol being oxidised in a –2e–/–H+ process to form a phenoxonium cation (similar to the experiments in non-aqueous solvents), which underwent rapid reaction with water (or –OH¯ at pH > 7) and rearrangement to form α-tocopherol quinone in a chemically irreversible process.
Electrochemical experiments were also performed by incorporating α-tocopherol into lecithin multilayers deposited onto the electrode surfaces. The results were very similar to those obtained for pure α-tocopherol films. α-tocopherol was oxidised to α-tocopherol quinone within the lecithin multilayers. However, the reduction process of α-tocopherol quinone appeared to be less chemically reversible as the pH was increased above pH 7. Two methods were used to incorporate α-tocopherol within the lecithin multilayers and both methods yielded similar electrochemical results. |
| first_indexed | 2024-10-01T03:03:48Z |
| format | Thesis |
| id | ntu-10356/44564 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T03:03:48Z |
| publishDate | 2011 |
| record_format | dspace |
| spelling | ntu-10356/445642023-02-28T23:34:47Z Voltammetric studies on vitamin E in organic solvents and within lipid bilayer membranes Yao, Wei Wei Richard David Webster School of Physical and Mathematical Sciences DRNTU::Science::Chemistry::Physical chemistry::Electrochemistry A series of model tocopherol compounds with differing degrees of methyl substitution around the aromatic ring were studied by variable scan rate (0.1- 500 V s-1) cyclic voltammetry experiments in CH3CN and CH2Cl2. On short voltammetric timescales α-TOH is oxidised in a chemically reversible –2e–/–H+ process to form a phenoxonium cation (α-TO+). The equilibrium and rate constants associated with the chemical steps were estimated by digital simulations of the variable scan rate data over a range of temperatures (T = 253-313K). α-Tocopherol films were deposited on the surface of gold, glassy carbon and platinum electrodes and their voltammetric behavior examined in aqueous solutions between pH 3 and 13. The voltammetric mechanism involved α-tocopherol being oxidised in a –2e–/–H+ process to form a phenoxonium cation (similar to the experiments in non-aqueous solvents), which underwent rapid reaction with water (or –OH¯ at pH > 7) and rearrangement to form α-tocopherol quinone in a chemically irreversible process. Electrochemical experiments were also performed by incorporating α-tocopherol into lecithin multilayers deposited onto the electrode surfaces. The results were very similar to those obtained for pure α-tocopherol films. α-tocopherol was oxidised to α-tocopherol quinone within the lecithin multilayers. However, the reduction process of α-tocopherol quinone appeared to be less chemically reversible as the pH was increased above pH 7. Two methods were used to incorporate α-tocopherol within the lecithin multilayers and both methods yielded similar electrochemical results. DOCTOR OF PHILOSOPHY (SPMS) 2011-06-02T06:31:10Z 2011-06-02T06:31:10Z 2011 2011 Thesis Yao, W. W. (2011). Voltammetric studies on vitamin E in organic solvents and within lipid bilayer membranes. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/44564 10.32657/10356/44564 en 185 p. application/pdf |
| spellingShingle | DRNTU::Science::Chemistry::Physical chemistry::Electrochemistry Yao, Wei Wei Voltammetric studies on vitamin E in organic solvents and within lipid bilayer membranes |
| title | Voltammetric studies on vitamin E in organic solvents and within lipid bilayer membranes |
| title_full | Voltammetric studies on vitamin E in organic solvents and within lipid bilayer membranes |
| title_fullStr | Voltammetric studies on vitamin E in organic solvents and within lipid bilayer membranes |
| title_full_unstemmed | Voltammetric studies on vitamin E in organic solvents and within lipid bilayer membranes |
| title_short | Voltammetric studies on vitamin E in organic solvents and within lipid bilayer membranes |
| title_sort | voltammetric studies on vitamin e in organic solvents and within lipid bilayer membranes |
| topic | DRNTU::Science::Chemistry::Physical chemistry::Electrochemistry |
| url | https://hdl.handle.net/10356/44564 |
| work_keys_str_mv | AT yaoweiwei voltammetricstudiesonvitamineinorganicsolventsandwithinlipidbilayermembranes |