Iodimetric assay of olanzapine in pharmaceuticals using iodate and Nile blue as reagents

Abstract

A simple, selective and cost effective spectrophotometric method has been described for the determination of olanzapine (OLP) in bulk drug and in tablets. The method involves treating OLP with an excess of iodate in acid medium followed by the determination of liberated iodine by reacting with a fixed amount of Nile blue and measuring the absorbance at 400 nm. In this method, the amount of iodine reacted corresponds to the OLP concentration. The experimental conditions for the assay have been optimized and the absorbance is found to increase linearly with the concentration of OLP (r = 0.997). Beer’s law is obeyed over the range 15-120 μg mL-1. The calculated molar absorptivity and Sandell sensitivity values are 0.657103 l mol-1 cm-1 and 0.475 μg cm-2, respectively. The limits of detection (LOD) and quantification (LOQ) are 3.93 and 11.90 μg ml-1. The performance of the method was validated according to the present ICH guidelines. The repeatability and intermediate precision, expressed by the RSD was better than 3%. The accuracy of the method expressed as relative error was satisfactory. The proposed method was applied to the analysis of tablet form of OLP and the results tallied well with the label claim. No interference was observed from concomitant substances normally added to tablets. The results were statistically compared with those of a literature method by applying the Student’s t-test and F-test. The accuracy and validity of the method were further ascertained by performing recovery studies via spike method.

Keywords

• olanzapine
• assay
• spectrophotometry
• iodate
• pharmaceuticals
• Nile blue