DETERMINATION OF PHLOROGLUCINOL IN PRESENCE OF PHLORETIN USING A MODIFIED VANILLIN REAGENT

A modification of the vanillin-HCl reagent has been applied to the assay of phloroglucinol in the presence of phloretin. The interference of phloretin in the assay was reduced to acceptable levels, and the modified reagents permitted the satisfactory assay of the phloretin hydrolase from Erwinia herbicola, which was not possible with the original reagent of Zaprometov (1). In the modified method, 0-25 μg of phloroglucinol in water was treated with 4.5 ml concentrated HCl, followed by 0.5 ml of 1.0% vanillin in absolute ethanol. The absorbance of the mixture was read at 480 mμ any time between 2 and 20 min after mixing. Phloretin gave a low response to the reagent. Phloretic acid, phloridzin, and catechol did not react, whereas resorcinol strongly reacted with both the original and modified reagents. © 1969.