Determination of Urea in Blood and Urine with Diacetyl Monoxime-glucuronolactone Reagent.

N UMEROUS STUDIES have been reported in the literature on the photometric determination of urea in biological fluids with diacetyl monoxime as the color-developing agent. The reaction is photosensitive, does not follow Beer’s law, and requires special precautions for reproducible results. In many proposed procedures, oxidants were added in the reaction mixture to destroy hydroxylamine which might be generated during the reaction by the strong acidity, and decrease the produced color. The oxidants employed have included persulfuric acid (5, 8, 12, 17), arsenic acid (1,2,6,10,19,20), perchioric acid (ii), chloramine T (9), and ferric ammonium sulfate (18). Substances other than oxidants have also been added to the reaction mixture: phenylanthranilic acid (21) and phenazone (3) to intensify the color and, more recently, thiosemicarbazide (4) to minimize the photosensitivity of the reaction. n-Glucuronolactone or n-glucuronic amide was found, in the authors’ laboratory, to produce an intense and photostable color when added to the reaction mixture. A simple, accul-ate, and reproducible method for determination of urea ill blood and urine was then developed utilizing this reaction.