Simple and Selective Spectrophotometric Determination of Ofloxacin in Pharmaceutical Formulations Using Two Sulphonphthalein Acid Dyes

Two new simple and sensitive extn.-free spectrophotometric methods were established for the detn. of ofloxacin (OFX). The methods are based on ion-pair complex formation reaction between OFX and acidic sulfonphthalein dyes, bromocresol purple (method A) and bromocresol green (method B) in dichloromethane. The exptl. variables such as reaction medium, reaction time, and reagent concn. were carefully optimized to achieve the highest sensitivity. Both dyes react spontaneously with OFX to give yellow-colored complexes. Beer's law is obeyed over the concn. ranges of 1.0-16 μg ml-1 OFX with correlation coeff. of 0.999 in both methods. The molar absorptivity values are calcd. to be 2.40 × 104 and 1.97 × 104 lmol-1 cm-1, for method A and method B, resp., with corresponding Sandell's sensitivity values of 0.015 and 0.019 μg cm-2. The limits of detection (LOD) and quantification (LOQ) are also reported. A Job's plot of the absorbance vs. the molar ratio of OFX to each of dyes under consideration indicated (1:1) ratio and the conditional stability const. (KF) of the complexes were calcd. The proposed methods were applied successfully to the detn. of OFX in tablets with good accuracy and precision and without interference from common additives. The results obtained by the proposed methods were compared favorably with those of the ref. method. [on SciFinder(R)