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The Determination of Guanidine Bases in the Blood.

1927; SAGE Publishing; Volume: 24; Issue: 7 Linguagem: Inglês

10.3181/00379727-24-3531

1535-3702

C. J. Weber,

Chemical Analysis and Environmental Impact

Recently, Pfiffner and Myers, in a preliminary report, gave a tentative procedure for the determination of the guanidine bases in blood. In an attempt to apply this method it was found that recoveries of added guanidine in amounts as small as 1 mg. per 100 cc. of blood could not be made. The main difficulty in the determination of these small amounts is the fact that the reagent proposed by Marston does not give a sufficient color production with guanidine in amounts smaller than 0.05 mg. per 5 cc. of solution. It was found that by replacing potassium ferrocyanide with ferricyanide, and eliminating the hydrogen peroxide, a reagent is produced which retains practically all the advantages of Marston's reagent, and in addition gives almost twice as much color with guanidine. The reagent is made by mixing equal volumes of 10 per cent solutions of sodium nitroprusside, potassium ferricyanide, and sodium hydroxide and diluting the mixture with three volumes of water. The color changes from a dark red to a pale yellow in about 20 minutes and is then ready for use. This prepared reagent will usually keep for 12 hours, but if turbidity develops a fresh reagent should be made up. It is used in the proportion of 1 cc. of the reagent to every 5 cc. of the solution to be tested. Equal amounts of guanidine or methyl guanidine give the same color value with the reagent, whereas dimethyl guanidine gives only two-thirds as much color. The color is an orange red, which develops to its maximum in 2 minutes. Creatine gives 1/10 as much color as does guanidine, and the color develops to its maximum in about 5 minutes.