Tropical Journal of Pharmaceutical Research

Original Research Article | OPEN ACCESS

Development of vanadometric system for spectrophotometric determination of timolol in pure and dosage forms

Charles O Nnadi¹ , Wilfred O Obonga¹, John DN Ogbonna², Linus O Ugwu³

¹Department of Pharmaceutical and Medicinal Chemistry; ²Department of Pharmaceutics; ³Department of Veterinary Medicine, University of Nigeria, Nsukka, 410001, Nsukka.

For correspondence:- Charles Nnadi Email: chasnnadi@yahoo.com Tel:+2348064947734

Received: 25 December 2014 Accepted: 30 September 2015 Published: 27 December 2015

Citation: Nnadi CO, Obonga WO, Ogbonna JD, Ugwu LO. Development of vanadometric system for spectrophotometric determination of timolol in pure and dosage forms. Trop J Pharm Res 2015; 14(12):2223-2229 doi: 10.4314/tjpr.v14i11.11

© 2015 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: To develop a simple vanadometric spectrophotometric method for the assay of timolol.

Methods: The oxidation reactions were performed at optimum conditions of 3 mL 20 % v/v H₂SO₄, 6.5 % w/v ammonium metavanadate, 40 - 60 ºC and 5 min for full colour (blue) development. The proposed method was validated in accordance with International Council on Harmonization (ICH) guidelines Q2 (R1) and applied to assay commercial timolol.

Results: Oxidation of timolol occurred at 504 nm wavelength. The developed method recovered 99.25 - 102.00 % of timolol in pre-analyzed formulations and 99.85 - 102.00 % of the manufacturers’ claim in commercial samples with RSD < 2 %. Linearity of 2 - 20 ppm (R² = 0.9995),as well as accuracy, 98 - 101 %; precision, 0.98 % (intraday) and 1.25 % (interday); robustness, 0.95 %; LOD, 0.256 ppm; LOQ, 0.425 ppm; and robustness, 0.95 - 1.10 %, were obtained.

Conclusion: The developed method is simple, sensitive, low-cost, accurate, reproducible, robust and rugged, and compares well with some complex methods for assay of timolol maleate in pure and dosage forms.

Keywords: Ammonium metavanadate, Spectrophotometry, Vanadometric, Timolol