GREMBERA-VINOGRADOVOY METHOD (L. Grimbert, fr. chemist, 1860 — 1931; I. L. Vinogradova, the Soviet biochemist) — quantitative determination of content of urea in blood serum and urine; is option of a gipobromitny method of definition of urea, in Krom pure bromine is replaced with its strong solution in bromic potassium. At the same time release of nitrogen considerably accelerates and happens in 5 — 7 min.
The method is based on the hydrolysis of urea sodium hypobromite in alkaline condition which is followed by formation of gaseous nitrogen, volume to-rogo is measured. Reaction proceeds on the following equation:
CO(NH 2 ) 2 + 3NaBrO → N 2 + CO 2 + 3NaBr + 2H 2 O.
Definition of the emitted nitrogen was carried out by Grember in at the reometr shipped in mercury, I. L. Vinogradova (1967) used the device of Kovarsky (fig.) to this purpose.
The course of definition
Serum proteins besiege 25% solution trichloroacetic to - you. For this purpose serum is mixed with trichloroacetic to - that in the ratio 1:1 and centrifuged. Kovarsky's device is filled with the NaCl and KCl solution prepared at the rate of 350 g of NaCl and 150 g of KCl on 1 l of water.
Enter into an upper tube of the device (3) trichloroacetic tsentrifugat (5,0 ml), lower it in the descending part of a tube (4), opening the crane of the device (1). In the same way consistently enter 42% NaOH solution (2,0 ml) and 6,0 ml of gipobromitny solution (55 ml of 42% of NaOH, 0,2 g of potassium iodide into 100 ml) (solution A); 50 g of potassium bromide dissolve in hot a dist, water, after cooling add 8,5 ml of bromine to it and bring water to 100 ml (solution B); ex tempore mix equal volumes of solutions A and B.
When formation of gas comes to an end, its volume is counted on scale graduations of the device. By means of a three-way cock (2) exempt the device from the formed gas and reaction mixture. Then repeat all definition with standard solution of urea.
Standard solution of urea is processed as blood serum, excepting addition trichloroacetic to - you.
During the definition of urea of urine the last is previously parted a dist, water by 5 times.
Calculation of amount of urea on 1 l of blood serum in grams is made on the following formula: V/V 1 • 0,0025 • 1000/2,5 = number of grams of urea on 1 l, where V — the volume of the gas emitted from blood serum; V 1 — the volume of the gas emitted from standard solution of urea; 2,5 — amount of blood serum in 5 ml trichloroacetic a tsentrifugata; 0,0025 — the number of grams of urea in 5 ml of standard solution of urea.
Normal concentration of urea in blood serum makes 20 — 40 mg of %. With urine 20 — 35 g of urea are allocated per day. At an acute renal failure the content of urea in blood reaches 300 — 500 mg of %, sometimes 800 mg of %; at the same time release of urea with urine almost stops (1 — 1,5 g per day).
Hypobromite reacts not only with urea, but also with other compounds of nitrogen containing amino groups. Therefore gipobromitny methods of definition of urea concede in specificity and accuracy to enzymatic methods using urease and to diatsetilmonooksimny methods.
Bibliography: Biochemical methods of a research in clinic, under the editorship of A. A. Pokrovsky, page 98, M., 1969; Vinogradova I. L. Rational modification of a gipobromidny method of definition of urea in blood and urine, Laborat, business, No. 4, page 217, 1967; Methodical instructions on use of the unified clinical laboratory methods of a research, under the editorship of V. V. Menshikov, page 66, M., 1973; G u i and of t J. et G of i m b e of t L. Pr6cis de diagnostic chimique, microscopique et parasitologique, p. 127, P., 1922.
L. H. Delektorskaya.