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Utility Of 3-Methyl-2-Benzothiazolinone Hydrazone Hydrochloride (MBTH) For Colorimetric Determination Of Some Drugs Containing Methoxyl Groups

Gamal H.Ragab, Manal S.Elmasry, Afaf A.Aboul Kheir

Simple, rapid and accurate method was described for the determination of mebevrine HCl (I), trimebutine maleate (II) and verapamil HCl (III) either in pure form or in pharmaceutical preparations. The method based on oxidation of the methoxyl groups of the cited drugs into the corresponding o-quinone, then coupling the resulted o-quinone for (I), (II) and (III) with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) to produce the corresponding coloured species. The wavelengths for maximum absorption were 670 nm for (I) and 640 nm for both (II) and (III), respectively. Beer’s law was obeyed in the concentration range 2-14, 1.25-5 and 0.5-2.5 mg/ml for (I), (II) and (III) respectively. The corresponding molar absorptivities were 0.295×103, 0.435×103 and 104 L.mol.-1cm-1 for (I), (II) and (III), respectively. Sandell’s sensitivities were also calculated. Results of analysis of pure drugs by the proposed method were in good agreement with the official and reference methods. The proposed method was successfully applied for the determination of these drugs in their pharmaceutical dosage forms without interference from other ingredients or common additives.