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

A new spectrophotometric method is proposed for 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 pH 9.00 at 50 °C to give an intense red colored chelate having maximum absorption at 480 nm. The optimization of the experimental conditions is described. The method has been used for the determination of 2.0–50.0 μg/ml of PEH. The molar absorptivity is 5.34×103 L.mol.-1cm.-1 and the accuracy of the method is achieved by the value of average recovery (101.28 %) and the precision is supported by relative standard deviation (RSD=1.25 %) values. The results of the method was compared with those of the standard method. The interference of excipients was studied. 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.