Tropical Journal of Pharmaceutical Research

Original Research Article | OPEN ACCESS

Spectrophotometric Determination and Thermodynamic Parameters of Charge Transfer Complexation Between Stavudine and Chloranilic Acid

Wilfred O Obonga, Edwin O Omeje , Philip F Uzor, Malachy O Ugwu

Department of Pharmaceutical and Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Nigeria, 41000, Nsukka, Nigeria;

For correspondence:- Edwin Omeje Email: winnomeje@yahoo.com Tel:+234803 5495441

Received: 27 February 2011 Accepted: 29 October, 2011 Published: 25 December 2011

Citation: Obonga WO, Omeje EO, Uzor PF, Ugwu MO. Spectrophotometric Determination and Thermodynamic Parameters of Charge Transfer Complexation Between Stavudine and Chloranilic Acid. Trop J Pharm Res 2011; 10(6):817-823 doi: 10.4314/tjpr.v10i6.16

© 2011 The authors.
This is an Open Access article that uses a funding model which does not charge readers or their institutions for access and distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0) and the Budapest Open Access Initiative (http://www.budapestopenaccessinitiative.org/read), which permit unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited..

Abstract

Purpose: The official assay methods for most antiretroviral drugs are limited by cost and unavailability of good test equipment in several developing countries. Therefore, this study investigates the use of charge transfer complexation in the spectrophotometric assay of stavudine as an alternative method to conventional methods.

Methods: Charge transfer complex formation between stavudine (n-donor) and chloranilic acid (p-acceptor) in 1,4-dioxan using a spectrophotometer was employed. Thermodynamic parameters of the complex formed were determined. The proposed method was employed in the analysis of commercially available stavudine dosage form.

Results: The wavelength of maximum absorption (λ_max) of the complex was at 526 nm compared to 457 nm for p-acceptor alone. Beer’s law was obeyed in the range of 5 - 40 mg % while the stoichiometry of the complex was found to be 2:1. The complex formed was still stable 24 h later. Its formation was spontaneous with a ΔH^oof -3.78×10³J/mol. The standard entropy change was from 12.18 ± 0.78 to 11.08 ± 1.23 cal/deg/mol over the temperature range of 30 - 60 ^oC while molar absorptivity decreased from 2.45×10⁵to 1.2×10⁵ over the same temperature range. The assay result of the standard stavudine solution was of high accuracy with a recovery value of 99.85 ± 1.95 %.

Conclusion: The proposed method is reliable and reproducible and should be suitable for the quality control of stavudine in bulk and dosage forms.

Keywords: Assay, Charge transfer, Stavudine, Spectrophotometric analysis, Chloranilic acid, Thermodynamic