Ultramicrodetermination of Plasma Urea by Reaction with Diacetylmonoxime—Antipyrine without Deproteinization

Abstract

Urea can be directly determined in serum or plasma by reaction with diacetylmonoxime—antipyrine: 5 µl of the sample is mixed with 5 ml of the chromogenic reagent, and the mixture is boiled 15 min, cooled, and read at 460 nm. The color is stable for 30 min in the light. The reagent is composed of (a) 0.4 g of antipyrine per 100 ml of H₂SO₄ (20 ml/100 ml), containing 5 mg of ferric sulfate per 100 ml: 1 (or 2) volume(s), and (b) 0.5 g of diacetylmonoxime per 100 ml of acetic acid (5 ml/100 ml): 1 volume.