Sensitive spectrophotometric methods for quantitative determination of gatifloxacin in pharmaceutical formulations using bromate-bromide, thiocyanate and tiron as reagents

Two simple, sensitive and rapid methods are described for the determination of gatifloxacin sesqui hydrate (GTF) in bulk drug and in formulations using bromate-bromide as the oxidimetric reagent. The methods are based on the oxidation of GTF by in situ generated bromine followed by determination of unreacted bromine by two different reactions. In one procedure, the residual bromine is reduced by an excess of iron(II), and the resulting iron(III) is complexed either with thiocyanate and measured at 470 nm (method A) or with tiron at pH 1.09 and measured at 670 nm (method B). In both methods, the absorbance is found to decrease linearly with GTF concentration. Beer's law is obeyed over the ranges 0.3-3.0 and 1-15 μg/mL for method A and method B, respectively. The calculated molar absorptivity values are 1.3 x 105 and 2.5 x 104 L/mol/cm for method A and method B, respectively. The methods were successfully applied to the determination of GTF in formulations and the results tallied well with the label claim. The results were statistically compared with those of a literature method by applying the Student's t-test and F-test. No interference was observed from the concomitant substances normally added to preparations. The accuracy and validity of the methods were further ascertained by performing recovery experiments via standard-addition method