A Color Reaction of 1, 2-Diphenols Based on Colored Complex Formation with Phenylfluorone and Iron (III) and Its Application to the Assay of Catecholamines in Pharmaceutical Preparations

Abstract

A color reaction of 1, 2-diphenols, such as catecholamines (CA), caffeic acid and gocypol, utilizing colored complex formation among a 1, 2-diphenol, an organic reagent and a metal ion was studied, and suitable conditions for the spectrophotometric determination of 1, 2-diphenols [as norepinephrine (NE), a CA] with phenylfluorone and iron (III) were established. The optimum pH range for the formation of colored complexes in the presence of polyoxyethylene monolauryl ether was pH 8.9-9.9. In the case of NE, the method could be used to determine up to ca. 10μg/10ml, and the apparent molar absorptivity at 630nm was 1.7×10⁵dm³mol^-1cm^-1. This method was applied to the assay of CA in commercial pharmaceutical preparations. A detection test for CA on a spot plate was also examined.