Use of haematoxylin in the spectrophotometric determination of alkaloids in pharmaceuticals, galenicals and powdered plants

Abstract

A simple and sensitive method for the determination of about fifteen alkaloids is described. The procedure is based on the reaction of the alkaloids with haematoxylin reagent in aqueous medium to give a red–violet colour (λ_max= 555 nm). Several variables affecting the colour development were studied and optimized. The method was used to determine 2–40 µg ml^–1 of the final measured alkaloidal base solution. There was a considerable increase in the absorptivity, which was dependent on both the basicity (pK_a) and molar concentration of the alkaloid present. The simplicity of the method permits rapid analysis, suitable for routine quality control. The interference of about 28 substances which are commonly prescribed with alkaloids was studied. No interference due to additives commonly present in the pharmaceutical preparations was observed. The method could be applied for the analysis of alkaloids in pure and pharmaceutical dosage forms, galenicals and powdered plants.