A new approach to the spectrophotometric determination of metronidazole and tinidazole using p-dimethylaminobenzaldehyde

Abstract

Nitro derivatives of five-membered heterocyles are of considerable interest. Some are biologically active with anti-inflammatory or vasodilatory activity (1). The 5-nitroimidazoles are used as antiamoebic, antiprotozoal and antibacterial agents. Two important members of this chemical class are metronidazole and tinidazole. Discovery of the anti-trichomonal properties of metronidazole revolutionized the treatment of disease. A new approach to the spectrophotometric determination of metronidazole (MZ) and tinidazole (TZ) has been developed. The procedure involves coupling of diazotized nitroimidazoles with p-dimethylaminobenzaldehyde (DMAB) to form a greenish-yellow solution. Optimal temperature and time were 0°C (iced) and 3 minutes for diazotization and 30°C and 2 minutes for coupling for both MZ and TZ. Coloured adducts of MZ and TZ showed shoulders at 406 nm and 404 nm, respectively, which were selected as analytical wavelengths. The reaction with p-DMAB occurred in a 1:1 mole ratio. Beer's law was obeyed within the 4.8-76.8 mg mL -1 concentration range with low limits of detection. The azo adducts were stable for over a week. Molar absorptivities were 1.101 0 3 (MZ) and 1.30´10 3 L mol -1 cm -1 (TZ). Overall recoveries of MZ and TZ from quality control samples were 103.2 ± 1.3 and 101.9 ± 1.3 % over three days. There was no interference from commonly utilized tablet excipients. No significant difference was obtained between the results of the new method and the BP titrimetric procedures. The azo approach using the p-dimethylaminobenzaldehyde procedure described in this paper is simple, fast, accurate and precise. It is the first application of DMAB as a coupling component in the diazo coupling reaction.

Development of a Visible Spectrophotometric Method for the Analysis of Ganciclovir in Bulk Sample and Dosage Form

“…In addition, a combined influence of the activating orthodirecting tertiary amino group and the metadirecting aldehyde group made the 3-and 5-positions on the DMAB moiety available to an incoming electrophile. The successful use of DMAB as coupling agent for diazotizable groups including primary amino groups and reducible nitro groups present on aromatic skeletons have been demonstrated [16,22]. As previously reported, the utilization of alcoholic solution (particularly methanol) repressed the deactivating influence of aldehyde group while the activating potential of the dimethylamino group was optimal.…”

Voltammetric determination of tinidazole in pharmaceutical tablets using carbon paste electrode

“…Analytical methods including HPLC [14][15][16][17] with different detectors and spectrophotometry [7,[18][19][20][21][22][23] have been reported on the determination of tinidazole in tablet, urine, and biological fluids. Since most of the conventional methods reported need trained personnel to operate, are expensive and not environmentally friendly, the development of electrochemical methods which are selective, sensitive, cheap and environmentally friendly is central.…”

Kinetic spectrophotometric determination of an important pharmaceutical compound, pregabalin

“…pDMAB possesses some peculiar structural features which account for its applicability in a wide range of reactions and processes. Its condensation reactions have been utilized for the spectrophotometric determination of many drugs (Adegoke and Umoh 2009;Adegoke and Nwoke 2008). An attempt has been made to develop a simple, accurate, rapid and economical method for determination of pregabalin in pure and pharmaceutical formulations.…”