Sensitive and Selective Methods for the Determination of Olanzapine in Pharmaceuticals Using N-bromosuccinimide and Two Dyes

Three indirect methods for the quality control of olanzapine (OLP) in commercial formulations based on titrimetric and spectrophotometric techniques are described using N-bromosuccinimide (NBS) and two dyes, namely amaranth and janus green B as reagents. In titrimetry, a measured excess of NBS is added to an acidified solution of OLP and the unreacted NBS is determined iodometrically. Spectrophotometry involves the addition of a known excess of NBS to OLP in acid medium followed by estimation of residual NBS by reacting with a fixed amount of either amaranth and measuring the absorbance at 520 nm (method A) or janus green B and measuring the absorbance at 620 nm (method B). Titrimetric procedure is applicable over the range 0.5-5.0 mg OLP, and the reaction stoichiometry is found to be 1: 6 (OLP: NBS). The spectrophotometric methods are applicable over the ranges 0.1-0.9 μg/ml (method A) and 0.1-1.2 μg/ml (method B). The proposed methods have been applied successfully for the determination of OLP in pure form and in its dosage forms and the results were compared with those of a literature method by applying the Student’s t-test and F-test. The validity of the methods was established by recovery studies.