Guest-host complex formed between ascorbic acid and β-cyclodextrin immobilized on the surface of an electrode

Area of Science:

• Electrochemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Ascorbic acid (AA) is a vital biomolecule with significant antioxidant properties.
• Beta-cyclodextrin (β-CD) is a host molecule capable of forming inclusion complexes with various guests.
• Carbon paste electrodes (CPEs) are versatile platforms for electrochemical sensing applications.

Purpose of the Study:

• To investigate the formation of supramolecular complexes between ascorbic acid (AA) and β-cyclodextrin (β-CD).
• To explore the electrochemical behavior of AA when immobilized on a β-CD-modified carbon paste electrode (CPE).
• To determine the thermodynamic parameters of the inclusion complex formed between the AA oxidation product and β-CD.

Main Methods:

• Potentiodynamic immobilization of β-cyclodextrin on a CPE surface to form a poly-β-CD modified electrode.
• Electrochemical studies, including voltammetry, were performed on bare CPE and modified CPE.
• Analysis of experimental data to determine Gibbs' standard free energy of inclusion.

Main Results:

• Surface immobilization of AA via inclusion complex formation with β-CD on the modified CPE.
• Adsorption of AA became the rate-limiting step for its electrochemical oxidation on the modified electrode.
• The Gibbs' standard free energy of inclusion for the AA oxidation product-β-CD complex was determined as -36.4 kJ/mol.

Conclusions:

• The poly-β-CD modified CPE effectively immobilizes AA through supramolecular complexation.
• This immobilization significantly influences the electrochemical oxidation pathway of AA.
• The study provides the first determination of the thermodynamic stability of the inclusion complex formed by the AA oxidation product and β-CD.