Tropical Journal of Pharmaceutical Research
Official Journal of Pharmacotherpy Group
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Novel colorimetric assay of mefenamic acid using 4-amino-3,5-dinitrobenzoic acid (ADBA)

SO Idowu^†, SC Tambo, AO Adegoke and AA Olaniyi

Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Ibadan, Ibadan.

Trop J Pharm Res, June 2002; 1(1): 15-22

Abstract Full-Text

Purpose: To develop a novel colorimetric assay method for mefenamic acid capsules.

Method: The new method (aromatic ring derivatization technique) is based on a diazo coupling reaction using diazotized 4-amino-3,5-dinitrobenzoic acid (ADBA) as a chromogenic derivatizing reagent.

Result: Optimization studies showed that the coupling reaction is very fast and completed in less than 1 minute. A 1:1 drug to reagent stoichiometric ratio was obtained for the azo dye formed. The azo adduct formed exhibits bathochromic shift with absorption maximum (l_max) at 490 nm, which was selected as the analytical wavelength. Lower limit of quantitation of mefenamic acid was 1 mg/ml. The assays were linear over the concentration range of 1 - 6 mg/ml and reproducible. This new method has been successfully applied in the assay of mefenamic acid capsules with accuracy similar to the official (B.P) titrimetric method of assay (p>0.05) and has the advantages of speed, high sensitivity, lower limit of detection and can be automated.

Conclusion: The method developed could find application in in-process quality control of mefenamic acid capsules.

Keywords: Mefenamic acid assay, 4-amino-3,5-dinitrobenzoic acid, colorimetry, diazotization.

^†To whom correspondence should be addressed. E-mail: olakunleid@yahoo.com  Tel: +234 802 3094981

@2002. TJPR Faculty of Pharmacy, University of Benin, Benin City, Nigeria

Tel: +234 802 3360318 Fax: +234 52 602257 E-mail: okhamafe@uniben.edu erah@uniben.edu p_erah@yahoo.com

Last updated: August 2002