Stability‐Indicating HPLC Method for the Determination of Quetiapine: Application to Tablets and Human Plasma

A stability‐indicating reversed‐phase high performance liquid chromatographic method was developed for the analysis of the antipsychotic drug quetiapine. Quetiapine was determined in presence of two of its degradation products; quetiapine N‐oxide and quetiapine lactam. The analysis was carried out using a 250 mm×4.6 mm i.d., 5 µm particle size Zorbax SB‐Phenyl column. Mobile phase containing a mixture of acetonitrile and 0.02 M phosphate buffer (50∶50) at pH=5.5 was pumped at a flow rate of 1 mL/min with UV detection at 254 nm. The method showed good linearity in the range of 0.08–20 µg/mL with limit of detection (S/N=3) 0.03 µg/mL (3.3×10−8 M). The suggested method was successfully applied for the analysis of quetiapine in bulk, tablets, and human plasma with average recoveries of 99.96±1.25%, 101.37±0.481%, and 100.82±1.53%, respectively. The proposed method was also applied for the determination of quetiapine in the presence of some co‐administered drugs as clomipramine, carbamazepine, and fluconazole.