Spectrophotometric Determination of Adrenaline, Phenylephrine Hydrochloride, and Terbutaline Sulfate Using the Gibbs Reagent

A spectrophotometric method has been developed for the determination of certain amine-phenol-containing drugs, namely, adrenaline, phenylephrine hydrochloride, and terbutaline sulfate. The method depends on the formation of new products by the reaction of drugs with the Gibbs reagent (2,6-dichloroquinone-4-chloroamide) in a basic borate buffer medium with a pH value of 11. The products were measured at 475, 652.5, and 547 nm for the aforementioned drugs, respectively. Beer–Lambert law was obeyed in the ranges of 0.3–9.5, 0.5–17, and 0.5–55 µg/mL with average recovery of 101.10, 99.13, and 99.78% and a relative standard deviation of ≤3.31%, respectively. The method was free from excipient interferences and applied successfully for the assay of the studied drugs in their pharmaceutical formulations. The resulting products were found in the ratio of 1 : 1.