Spectrophotometric Assay of Phenylephrine Hydrochloride Using 4-Aminoantipyrine and Copper (II)

A new spectrophotometric method is proposed for the determination of phenylephrine hydrochloride. The method is based on the coupling of 4-aminoantipyrine (4-AAP) with Phenylephrine Hydrochloride (PEH) to give a new ligand that reacts with copper (II) in the presence of sodium tetraborate buffer solution of pH9 at 50°C with an intensely red colored chelate having maximum absorption at 480 nm. The method has been used for the determination of 2.0–50.0 μg ml-1 of PEH with molar absorptivity of 5.357×103 L.mol-1cm-1, average recovery of 101.28 % and Relative Standard Deviation (RSD) of 1.25%. The results of the method were compared with those of the official method. The mechanism of the chemical reaction has been proposed. The proposed method was successfully applied for the determination of the PEH in pharmaceutical syrup formulations.