Spectrophotometric Methods for the Determination of Methotrexate in Pharmaceutical Formulations

Abstract

Abstract Three visible spectrophotometric methods (A-C) for the determination of Methotrexate (MTX) in pharmaceutical formulations are described. Method A is based on the reduction of Fe(III) to Fe(II) by the drug which forms a coloured complex (λmax: 510 nm) with 1,10-phenanthroline (PHEN). Method B involves the reduction of Folin-Ciocalteu (F-C) reagent by the drug and the reduced species produced possesses a characteristic intense blue colour (λmax: 770 nm). Method C is based on the coupling reaction through the involvement of an aromatic secondary amino group in p-N-methylaminobenzoylglutamic acid (released through reduction of the drug with zinc and HCl) with 1,2-naphthaquinone-4-sulfonic acid sodium salt (NQS) to form a coloured product (λmax: 500 nm). Regression analysis of a Beer's plot showed good correlation in the concentration ranges of 1.0–8.0, 2.0–14.0 and 25.0–300.0 μg.ml−1 for methods A,B and C, respectively. No interference was observed from the additives and the applicability of the meth...