Extraction Spectrophotometric Determination of Trace Amounts of Lorazepam in Pharmaceutical Formulations

A simple and sensitive extraction-spectrophotometric method for the determination of Lorazepam (LOR) in pharmaceutical formulations is reported. The LORH+ cation which is formed in an acidic solution can form an ion-pair with OR(II) anionic dye. The LORH+ - OR(II)- ion pair is quantitatively extraced into dichloromethane solvent and its absorption was measured at 482 nm. The calibration graph is linear over the LOR concentration range of 1.0-25.0 μg mL-1 and the regression coefficient is 0.9999. The relative standard deviation (RSD) of ten replicate determination of 10.0 μg mL-1 of LOR is 1.6% and the limit of detection, LOD, of the method is 4.8x10-2 μg mL-1. The method is successfully applied to the determination of LOR amount in pharmaceutical formulations (1.0 and 2.0 mg tablets).