Sensitive Spectrophotometric Methods for Quantitative Determination of Gatifloxacin in Pharmaceutical Formulations using Bromate-Bromide, Thiocyanate and Tiron as Reagents


  • Basavaiah Kanakapura University of Mysore
  • Anil Kumar Urdigere Rangachar University of Mysore


Gatifloxacin, spectrophotometry, complexation, pharmaceuticals, bromate-bromide


Abstract. 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 1.3×105 and 2.5×104 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 ttest 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.

Resumen. Se describen dos métodos simples, sensibles y rápidos para la determinación del sesquihidrato de gatifloxacina (GTF) como droga cruda y en formulaciones, empleando bromuro-bromato como el reactivo oxidimétrico. Los métodos se basan en la oxidación de GTF por bromo generado in situ seguido de la determinación del bromo excedente por dos reacciones diferentes. En un procedimiento, el bromo residual se reduce por exceso de Fe(II), y el Fe (III) resultante se compleja, ya sea con tiocianato y medido a 470 nm (método A) o con tiron a pH 1.09 y medido a 670 nm (método B). En ambos métodos se encuentra que la absorbancia decrece linealmente con la concentración de GTF. Se sigue la ley de Beer en los rangos de 0.3 – 3.0 y 1 – 15 μg /mL por el método A y por el método B, respectivamente. Los valores calculados de absorptividad molar son 1.3 × 105 y 2.5 × 104 L /mol /cm para los métodos A y B, respectivamente. Los métodos fueron aplicados exitosamente a las determinaciones de GTF en formulaciones y los
resultados coincidieron con lo informado en la etiqueta. Los resultados fueron comparados estadísticamente con los informados en la literatura empleando pruebas t de student y la prueba F. No se observaron interferencias con las substancias empleadas para el análisis. La exactitud y validez de los métodos fueron confirmados por experimentos de recuperación mediante el método estándar de adición.


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Author Biographies

Basavaiah Kanakapura, University of Mysore

Department of Chemistry

Anil Kumar Urdigere Rangachar, University of Mysore

Department of Chemistry


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