Utility of some π-Acceptors for Spectrophotometric Determination of Gatifloxacin in Pure Form and in Pharmaceutical Preparations

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Four simple, quick and sensitive methods are described for the spectrophotometric determination of gatifloxacin. The methods are based on the reaction of gatifloxacin as n-electron donor with 7,7,8,8-tetracyanoquin-odimethane (TCNQ) ; 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) ; chloranilic acid (CLA) and p-chloranil (CL) as π-acceptors to give highly colored complex species. The colored products are quantitated spectrophoto-metrically at 460, 841, 530 and 545nm for DDQ, TCNQ, CLA and CL, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the concentration ranges 5-60, 1.5-18, 30-360 and 20-240μg ml^<-1> of gatifloxacin, but for more accurate analysis, Ringbom optimum concentration range was found to be 7.5-55, 3-16, 35-350 and 25-230μg ml^<-1> of gatifloxacin for DDQ, TCNQ, CLA and CL, respectively. The limits of detection and quantification were calculated and the relative standard deviations for different concentrations of gatifloxacin using various acceptors were <1.28%. The association constants of 1: 1 complexes and standard free energy changes using Benesi-Hildebrand plots were studied. The proposed methods were successfully applied to the determination of gatifloxacin in pharmaceutical dosage forms without interference from common additives encountered.
2008-01-01