Determination of Lorazepam in Drug Formulation and Biofluids Using a Spectrophotometric Method and Response Surface Methodology

A novel, simple, sensitive, and selective kinetic spectrophotometric method has been developed for the determination of lorazepam in pharmaceutical and bioloical samples. The procedure is based on the catalytic effect of lorazepam on the Janus Green-bromate reaction system. The change in absorbance was followed spectrophotometrically at 618 nm. To obtain the maximum sensitivity, the reagents concentration, temperature, and time were optimized by one at the time method. Under optimum experimental conditions, the calibration curve was linear over the range 0.3-19.5 mu g/mL of lorazepam, including two linear segments. The relative standard deviations (n = 5) for 1.0, 5.0, and 15.0 mu mol/L of lorazepam were 1.09, 1.03, and 0.97%, respectively. The limit of detection was 0.08 mu g/mL of lorazepam. An experimental check under these optimal conditions confirmed good agreement in the RSM results. The developed method was successfully applied for the determination of lorazepam in real samples, and the obtained results are in a good agreement with those using HPLC.