Spectrophotometric Methods for Determination of Metronidazole in Pharmaceutical Formulations

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Shlair H. Hasan
Narmeen S. Abdullah


Metronidazole, Spectrophotometry, NBD-Cl, FCR, Pharmaceutical formulations


    Two new, simple and accurate spectrophotometric methods for determination of metronidazole (MET) have been proposed. The methods are based on the reduction of metronidazole with iron metal and hydrochloric acid then the subsequent of the formed reduction product which contains primary amino (NH2) group coupling with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) reagent to form a purple colored chromogen that measured spectrophotometrically at 546 nm (Method A). The method B depends on the reduction of tungstate and/or molybdate in Folin-Ciocaleteu reagent (FCR) by reduced metronidazole in alkaline medium to form a blue colored chromogen, which measured spectrophotometrically at 725 nm. Under optimized reaction condition, the reaction of reduced metronidazole with both NBD-Cl and FCR get a good linearity in the concentration range  of 0.3-30 and 0.5-40 μg/ ml for NBD-Cl and FCR, respectively. The limits of detection and quantitation were 0.16 and 0.56 μg/ml for method A; while for method B were 0.05 and 0.18 μg/ml, respectively.  The accuracy and precision of the proposed methods were satisfactory. The proposed methods were simple, rapid and successfully applied for analysis of MET in its pharmaceutical formulations.

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