SPECTROPHOTOMETRIC DETERMINATION OF ESZOPICLONE IN PURE AND PHARMACEUTICAL FORMS

Six spectrophotometric methods for determination of eszopiclone have been developed, validated and applied for the assay of the drug in pharmaceuticals. Methods A, B, C and D are based on ion pair complexation of drug, in acidic buffers, with triphenylmethane dyes viz., Bromothymol blue(BTB), Bromophenol blue(BPB), Bromocresol green(BCG) and Bromocresol purple(BCP). The complexes are extracted into chloroform and absorbance is measured around at 415 nm as function of concentration of the drug. The stoichiometry of the complex is found 1:1 in each case. Method E depends upon charge transfer complexation of neutralized drug with iodine which produces iodide ion whose absorbance at 366 nm is measured as function of concentration of the drug. This complex, too, has 1:1 composition as determined by Job's method. Method F is developed on the basis of oxidation of the drug with alkaline KMnO4 which generates green colored manganate ion with 610 nm. As the intensity of green color increased with increasing time kinetics of the reaction is followed and calibration curves are constructed by using initial rate and fixed time methods. Excellent recovery studies with high accuracy and precession indicate that the methods can be successfully used in industries for the assay of drug in pure form and pharmaceuticals.