An improved method for the determination of urine urea nitrogen by direct nesslerization

Abstract

Abstract 1.1. A new method for the determination of urea nitrogen in urine has been developed. The urine, if neutral or alkaline, is made just acid to litmus with glacial acetic acid, diluted, and treated with permutit to remove the ammonia. The urea in the urine is then hydrolyzed to ammonium carbonate by the action of a highly concentrated urease reagent in fifteen minutes at 50 °C. The concentrated urease and any other interfering proteins are then removed from the urine by treatment with tungstic acid. Urea nitrogen is determined colorimetrically, without turbidity interference, after nesslerization of the filtrate. 2.2. The above method for the determination of urine urea nitrogen is an application of the Taylor-Blair method for determining blood urea nitrogen. 3.3. In our hands this method for determining urine urea nitrogen values has proved comparable in accuracy to the standard aeration and titration methods. It has shown a high degree of accuracy in the recovery of urea added to urine. 4.4. The method offers a degree of ease and practicability of manipulation which allows many determinations to be made at the same time, requires no additional apparatus, and eliminates technical difficulties and inaccuracies of aeration and distillation procedures. 5.5. This method, when combined with the Taylor-Blair method for the determination of blood urea nitrogen, gives a marked degree of speed and accuracy, which makes the blood urea clearance determination as a clinical measure of kidney function readily available.