Extraction-Spectrophotometric Determination of Trace Amounts of Lorazepam in Pharmaceutical Formulation

Abstract

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 Orange(II) anionic dye the LORH⁺–OR(II)^– ion pair is quantitatively extracted 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 10 replicate determination of 10.0 μg mL^-1 of LOR is 1.6 % and the limit of detection (LOD) of the method is 4.8 × 10^-2 μg mL^-1. The method is successfully applied to the determination of LOR amount in pharmaceutical formations (1.0 and 2.0 mg tablets).