Application of Methyl Orange in the Spectrophotometric Determination of Citalopram and Dapotextine in Pharmaceutical Formulations

A simple, rapid and sensitive spectrophotometric method has been proposed for the assay of citalopram (CIT) and dapotextine (DPT) in bulk and pharmaceutical formulations. The method based on the reaction of the selected drugs with methyl orange (MO) in buffered aqueous solution at pH = 5.0 and pH = 3.0 for CIT and DPT, respectively. The formed yellow ion-pair complexes were extracted with dichloromethane and their absorbance was measured at 422 nm. The best conditions of the reaction were studied and optimized. The extracts are intensely colored and very stable at room temperature. The calibration graphs were linear over the concentration range of 1.2 – 4.8 mg/ml for CIT and 0.4 – 4.0 mg/ml for DPT. The drug–dye stoichiometric ratio as determined by the Job’s method was found to be 1:1. The proposed method was successfully applied for determination of the drugs in tablets with good accuracy and precision. Excipients used as additive in commercial formulations did not interfere in the analysis. The proposed method can be recommended for quality control and routine analysis where time, cost effectiveness and high specificity of analytical technique are of great importance.