Flow injection determination of metronidazole through spectrophotometric measurement of the nitrite ion produced upon alkaline hydrolysis

Abstract

Um novo método para determinação de metronidazol, baseado no monitoramento espectrométrico do sal de diazônio produzido in-line pelos íons nitrito, liberados numa hidrólise alcalina, foi desenvolvido e aplicado com sucesso a comprimidos (r = 0,9993, 2,0-20,0 mg L -1 , LD = 0,7 mg L -1 ), sem interferência de ingredientes comumente presentes.A new method for metronidazole determination, based on spectrometric monitoring of a diazonium salt produced in-line by alkaline hydrolysis released nitrite ions, was developed and successfully applied to pharmaceutical tablets (r = 0.9993, 2.0-20.0 mg L -1 , DL = 0.7 mg L -1 ) with no interference from common ingredients accompanying the drug. Keywords: flow injection analysis, spectrophotometry, pharmaceuticals, metronidazole, nitrite IntroductionMetronidazole (MTZ), 2-(5-nitro-2-methylimidazol-1-yl)-ethanol, likewise others nitroimidazole derivatives presents biological activity against anaerobic micro-organisms, being largely used as the active ingredient of antihelminthic medicines. 1 Thus, there is an important demand for rapid and simple methods for the determination of MTZ in pharmaceutical preparations. Methods based on HPLC and classical volumetric titration are recommended by the pharmacopoeia for the direct determination of MTZ. 2 Although this later one is kind of simple, being daily practiced in many routine analysis laboratories, it is time consuming and very tedious as it is based on the use of acetic anhydride. Various research studies have been devoted to the development of new high performance alternative methods for determination of the drug in dosage forms using different techniques such as high performance liquid chromatography, 3 supercritical fluid chromatography, 4 differential pulse polarography 5 and voltammetry with glassy carbon electrode 6 or chemically modified electrodes. 7 Flow analysis approaches have also being successfully applied on developing fast analytical methods for determination of some antihelmintic and antiprotozoal with spectrometric 8-10 and biamperometric detection in dosage forms. 11 The alkaline hydrolysis of MTZ releases the nitro group as nitrite ion and the reaction can be carried out in a quantitative way by controlling the pH, temperature and hydrolysis time. Thus, a simple measurement of the yielded nitrite ions can be used to determine MTZ. This approach has been taken advantage of to implement MTZ analytical procedures. [12][13][14] An assay based on measurement of the change in ultraviolet absorbance during the alkaline hydrolysis of the compound was proposed for determination of MTZ in oral suspensions. 12 Another one, based on colorimetric monitoring of the diazonium salt produced by a diazotizationcoupling reaction with the released nitrite ions, has long been proposed and optimized later on. 13,14 Despite the good selectivity and sensitivity of these procedures, they are time consuming and employ large amounts of reagents.This work describes a flow injection analysis (FIA) approach for determination of MTZ based o...

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

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HPLC method for simultaneous determination of metronidazole and preservatives in vaginal gel formulation

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