Highly sensitive spectrophotometric method for the quantitative determination of olanzapine in its pure and in pharmaceutical dosage forms

The present paper describes a simple, accurate and highly sensitive visible spectrophotometric method for the determination of olanzapine in pure drug and in pharmaceutical formulations. The proposed method is based on the formation of a colored charge - transfer complex by two steps. In the first Step, N-bromosuccinimide (NBS) oxidize olanzapine into its sulphoxide form, and in the second step, unreacted NBS oxidize metol to form p-N-methylbenzoquinonemonoimine (PMBQMI) which reacts with isonicotinic acid hydrazidc (INH) to form a colored complex and the resulting colored complex exhibit a maximum absorption peak at 610 nm. Beer's law was obeyed over the concentration range 0.4 - 8.0 mu g ml(-1) and the calculated molar absorptivity is 2.08 x 10(4) l mol(-1) cm(-1); and the corresponding limit of quantification (LOQ) was 0.3696 mu g ml(-1). All the variables were studied in order to optimize the reaction conditions. No interference from the excipients added to tablets was found. The results obtained in the proposed method has been compared statistically to the reference method and found to be simple, accurate (t-test) and reproducible (F-test) and can be used as an alternative for simple and routine determination of olanzapinc in microgram quantifies in industrial quality control laboratories.