Highly sensitive spectrophotometric determination of olanzapine using cerium(IV) and iron(II) complexes of 1,10-phenanthroline and 2,2′-bipyridyl

Abstract

Two highly sensitive spectrophotometric methods have been developed for the determination of olanzapine (OLP) in pharmaceuticals using cerium(IV) and iron(II) complexes of 1,10-phenanthroline and 2,2′-bipyridyl as reagents. The methods are based on the oxidation of OLP in acidic medium by a known excess of cerium(IV) followed by the determination of the unreacted oxidant by reacting with either ferroin and measuring the absorbance at 510 nm (method A) or iron(II)-2,2′-bipyridyl complex and measuring the absorbance at 525 nm (method B). The amount of cerium(IV) reacted corresponds to the amount of OLP. In both the methods, the absorbance is found to increase linearly with OLP concentration as shown by the correlation coefficient (r) of 0.9980 and 0.9958 for method A and method B, respectively. The calibration graphs are linear over the concentration range of 0.2–2.0 μg/mL in both the methods. The calculated molar absorptivity values are 1.00 × 106 and 7.03 × 105 L/mol cm, for method A and method B. The LOD and LOQ values for method A are calculated to be 0.04 and 0.13 μg/mL and the values are 0.07 and 0.22 μg/mL for method B, respectively. The methods were validated as per the current ICH guidelines. Both the methods gave similar results in terms of accuracy and precision. The RSD was less than 3% and the accuracy, obtained from recovery experiments, was 98.76–101.4%. The methods developed were applied to the determination of OLP in tablets and results agreed well with the label claim.