ABSTRACT
A modified urease hypochlorite method for measuring urea in biological fluids is described. Its novel feature is the use of 4-hydroxycoumarin as ammonia acceptor. This compound has never been used for this purpose, and it has a number of advantages over traditional phenol and its derivatives: the measurement is performed in just two steps, the compound is nontoxic and used in low concentrations, and the accuracy of measurements is higher due to decrease of the systemic error. Results of urea tests with the new kit are presented. The kit contains ready-to-use components in tablets and stabilized concentrated solutions of sodium hypochlorite and alkali. The characteristics of the kit are as follows: linearity of determination up to 25 mmoles per liter, deviation from linearity no more than 7%, and sensitivity up to 0.7 mmoles/liter.