BENEDIKTA METHODS (S. R. Benedict, 1884 — 1936, amer. the biochemist) — methods of determination of content uric to - you in blood and glucose in urine.
Definition of uric acid in blood. At the heart of the method offered by Benedict property uric lies to - you to recover a phosphatotungstic reactant with formation of connection of blue color. The phosphatotungstic reactant contains 100 g of sodium tungstate, 50 g of white arsenic, 25 ml of 85% of phosphoric and 20 ml concentrated salt to - you in 1000 ml of a distilled water.
Contents uric is normal to - you (determined by the described method) make 2,5 — 4 mg of %, but can, depending on the content of purines in food, reach 6 — 7 mg of %. The blood analysis on uric to - that is conducted after three-day considerable restriction of content of purines and fats in a diet of the patient.
Technology of definition. In a centrifugal test tube mix 0,2 ml of blood from 1,4 ml of a distilled water, 0,2 ml of 10% of sodium tungstate, 0,2 ml 2/3 N a chamois to - you and in 10 min. centrifuge. In one test tube measure 1 ml of nadosadochny liquid (that corresponds to 0,1 ml of blood), and in another — 1 ml of standard solution uric to - you which contains 0,004 ml uric to - you; add to each of test tubes on 1,8 ml 2,8% of aqueous solution of sodium cyanide and on 0,2 ml of a phosphatotungstic reactant, boil 3 min. on the water bath, cool and in 3 min. fotokolorimetrirut, determining concentration by the standard curve constructed for standard solution uric to - you or by a difference of a fotometrirovaniye of pilot and control tests.
Qualitative test of glucose in urine (Benedict's test). Ability of glucose to recover hydrate of copper oxide in alkaline condition in hydrate of cuprous oxide (yellow color) or in cuprous oxide (red color) is the cornerstone of a method. For binding of excess amount of hydrated copper oxide (that there was no formation of the copper oxide preventing definition) add sodium citrate to Benedict's reactant. Benedict's reactant contains 173 g of Na sodium citrate 3 With 6 H 5 O 7 · 11H 2 O, 90 g of sodium carbonate (anhydrous), 17,3 g of CuSO cuprous sulfate 4 · 5H 2 O in 1000 ml of water.
Benedikta test is the most sensitive and reliable in comparison with other tests similar to it — Gaynesa, Nilander, Trommer, Felinga (see Carbohydrates, methods of a research) since at big cultivations of urine (8 — 10 drops of urine in 5 ml of a reactant) the recovering effect of other reducing substances of urine is expressed poorly. About diagnostic value of detection of glucose in urine — see. Glycosuria .
Technology of definition. In a test tube mix 5 ml of a reactant of Benedict with 8 — 10 drops of urine and place for 2 min. in the boiling water bath. Coloring of liquid and the formed deposit changes depending on concentration of glucose. In the presence of sugar in urine (0,5 — 2%) green, yellow or red coloring of liquid with bottom sediment of a test tube appears. At green coloring without existence of a deposit — test negative.
See also Urine (research).
Bibliography: Biochemical methods of a research in clinic, under the editorship of A. A. Pokrovsky, page 268, M., 1969; K.S's Jambs. Clinical biochemistry, page 65, L., 1967
V. Ya. Maximov.