New Extractive Spectrophotometric Methods for the Determination of Olanzapine in Pharmaceutical Formulations Using Bromocresol Green

Two simple, rapid, accurate, and sensitive spectrophotometric methods have been described for the assay of olanzapine (OLP) in bulk and in pharmaceutical formulations. The first method (method A) is based on the formation of yellow ion-pair complex between the OLP and bromocresol green (BCG) at pH 5.50 ± 0.10. The ion-pair complex formed was extracted with dichloromethane and the absorbance was measured at 410 nm. The second method (method B) is based on the breaking of the yellow OLP-BCG ion-pair complex in alkaline medium after its extraction into dichloromethane followed by the measurement of the blue colour of the dye at 620 nm. Beer’s law is obeyed in the concentration ranges 0.25-12.50 μg/mL for method A and 0.2-5.0 μg/mL for method B. The molar absorptivity, Sandell sensitivity, detection and quantification limits are also calculated. The methods were validated for intra-day and inter-day accuracy and precision; selectivity and robustness and ruggedness. The proposed methods were applied successfully to the determination of OLP in their pharmaceutical formulations and the results were in good agreement with those obtained by the official method. The accuracy and reliability of the proposed methods were further ascertained by recovery studies via standard addition technique.