A Colorimetric Test for Guanidine

Abstract

In studies pertaining to muscular dystrophies, attention was given to the possibility that simple guanidine derivatives might play a part in the etiology of these abnormalities. Guanidine is a protoplasmic poison as early shown by Gergens and Baumann 1 for animals and Kawahita 2 for plants. Just what part it might play in the phenomena of health and disease has been problematical since satisfactory tests for guanidine in body fluids, tissues, and excretions have been lacking. Various color tests have been recommended for guanidine by Tieg, 3 Marston, 4 and Weber. 5 These tests have not been found satisfactory since they give color more or less with methyl guanidine which may be formed from creatine or creatinine by oxidation as early shown by Dessaignes, 6 and corroborated by Ewins, 7 Baumann and Ingvaldsen, 8 and by Greenwald. 9

Accordingly, a new test for guanidine NH:C(NH₂)₂ with a high degree of specificity was devised. This procedure runs as follows:

Color reaction for guanidine. To 1 cc. of an aqueous or decinormal hydrochloric acid solution of guanidine carbonate or hydrochloride, containing 0.5 mg. of guanidine base, add 1 cc. of a freshly made 1% solution of 1.2 naphthoquinone-4-sodium sulphonate followed by 0.3-0.5 cc. of N NaOH. Let stand 15 minutes at 20°C. or, better, 1-2 minutes in a boiling water bath. Cool under running tap water, add 0.3 cc. of a 25% urea solution and acidify with 1 cc. of concentrated HCl, mix, and add 1 cc. of concentrated HNO₃ (density 1.42). The guanidine solution becomes a bright red while other compounds tested, with a few exceptions later detailed, go to yellow. The guanidine reaction is definitely red with solutions containing 0.05 mg. guanidine per cc.