Sensitive Spectrophotometric Methods for the Determination of Gatifloxacin in Pharmaceuticals Using Bromate-Bromide, Methylene Blue and Rhodamine-B as Reagents

Two new simple, precise, rapid and extn.-free spectrophotometric methods are proposed for the detn. of gatifloxacin (GTF) using bromate-bromide mixt. and two dyes, methylene blue and rhodamine B, as reagents. Spectrophotometric methods entail the addn. of a known excess of bromate-bromide mixt. to GTF in hydrochloric acid medium followed by detn. of residual bromine by reacting with a fixed amt. of either methylene blue and measuring the absorbance at 665 nm (Method A) or rhodamine B and measuring the absorbance at 555 nm (Method B). Beer's law is obeyed in the ranges, 0.5-5.0 and 0.2-1.5 μg mL-1 for method A and method B, resp. The apparent molar absorptivities are calcd. to be 5.6 × 104 and 9.6 × 104 L mol-1cm-1 for method A and method B, resp., and the corresponding Sandell sensitivity values are 0.0071 and 0.0042 μg cm-2. The methods were successfully applied to the assay of GTF in pharmaceutical formulations with satisfactory results. [on SciFinder(R)