Spectrophotometric Estimation of Phenylephrine Hydrochloride via Oxidative Coupling Reaction with p-Aminobenzophenone

In this research, a rapid, simple and accurate spectrophotometric approach was described for the estimation of phenylephrine hydrochloride in the pure and in its drug forms. The suggested method was based on the oxidative coupling reaction of phenylephrine hydrochloride with p-aminobenzophenone using potassium periodate as an oxidant. A taupe-red dye was formed at room temperature and showed maximum absorption at 512 nm. The linearity of the standard calibration curve was compatible with Beer's law within the concentration range of 2.0-20 μg/mL with a determination coefficient (r2=0.9986). The apparent molar absorptivity and the sensitivity of Sandell's index were calculated and found to be in the values of 0.552x104 L/mol.cm. and 0.0368 μg/cm2, respectively. The nature of the resulting dye has been studied between phenylephrine hydrochloride to p-aminobenzophenoneand and it was equal to 1:1. The limits of detection (LOD) and quantification (LOQ) were estimated and found to be 0.0094 and 0.0313 μg/mL, respectively. A relative standard deviation and a relative error were also calculated and they will be in the range of 0.0715 to 0.0216 and -0.0479% to -0.0145%, respectively. The recommended procedure was applied to assay phenylephrine hydrochloride in drops and injection and no interferences were observed from the common additives found in the drugs.