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Noreen A, Anwar Z, Ahsan Ejaz M, Usmani M, Khan T, Ali Sheraz M, Ahmed S, Mirza T, Khurshid A, Ahmad I. Riboflavin (vitamin B 2) sensitized photooxidation of ascorbic acid (vitamin C): A kinetic study. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2024; 309:123813. [PMID: 38198998 DOI: 10.1016/j.saa.2023.123813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 12/01/2023] [Accepted: 12/23/2023] [Indexed: 01/12/2024]
Abstract
Ascorbic acid (AH2) photoxidation sensitized by riboflavin (RF) has been studied between pH 2.0 and 12.0 in ambient air and anaerobic environment using UV and visible irradiation sources. The kinetics of AH2 degradation in aqueous medium along with RF is found to be first-order for its photodegradation. AH2 photolysis rate constants in aerobic and anaerobic conditions with RF (1.0-5.0 × 10-5 M) are 0.14-3.89 × 10-2 and 0.026-0.740 × 10-2 min-1, respectively. The rate constants (k2) of second-order kinetics for AH2 and RF photochemical interaction in aerobic and anaerobic conditions are in the range of 0.24-3.70 to 0.05-0.70 × 10-3 M-1 min-1, respectively, which manifests that increasing the RF concentration also increases the rate of photodegradation (photooxidation) of AH2. The k2 versus pH graph is bell-shaped which indicates that increasing the pH increases photolytic degradation rate of AH2 with RF. Increasing the pH results in the increased ionization of AH2 (ascorbyl anion, AH-) and redox potential which leads to the higher rates of photodegradation of AH2. Two-component spectrophotometric (243 and 266 nm, AH2 and RF, respectively) and high-performance liquid chromatography (HPLC) methods have been used to determine the concentration of AH2 and RF in pure and degraded solutions. The results obtained from these two methods are compared using a student t-test which showed no noteworthy difference between them.
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Affiliation(s)
- Aisha Noreen
- Department of Pharmaceutical Chemistry, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Gadap Road, Super Highway, Karachi 75340, Pakistan
| | - Zubair Anwar
- Department of Pharmaceutical Chemistry, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Gadap Road, Super Highway, Karachi 75340, Pakistan.
| | - Muhammad Ahsan Ejaz
- Department of Pharmaceutical Chemistry, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Gadap Road, Super Highway, Karachi 75340, Pakistan
| | - Muneeba Usmani
- Department of Pharmaceutics, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Gadap Road, Super Highway, Karachi 75340, Pakistan
| | - Tooba Khan
- Department of Pharmaceutical Chemistry, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Gadap Road, Super Highway, Karachi 75340, Pakistan; Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Sindh, Allama I.I., Kazi Campus, Jamshoro 76080, Sindh, Pakistan
| | - Muhammad Ali Sheraz
- Department of Pharmaceutics, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Gadap Road, Super Highway, Karachi 75340, Pakistan
| | - Sofia Ahmed
- Department of Pharmaceutics, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Gadap Road, Super Highway, Karachi 75340, Pakistan
| | - Tania Mirza
- Department of Pharmaceutical Chemistry, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Gadap Road, Super Highway, Karachi 75340, Pakistan
| | - Adeela Khurshid
- Department of Pharmaceutics, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Gadap Road, Super Highway, Karachi 75340, Pakistan
| | - Iqbal Ahmad
- Department of Pharmaceutical Chemistry, Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Gadap Road, Super Highway, Karachi 75340, Pakistan
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