A micromethod for the determination of glycocyamine in biological fluids and tissue extracts

In the two following communications (1, 2) evidence is presented that glycocyamine is a normal precursor of creatine in the animal body. These studies required a satisfactory micromethod for the determination of glycocyamine. The most reliable method described in the literature consists in adsorption on Lloyd’s reagent in acid solution, elution with baryta, removal of arginine from the eluate by repeated adsorption on permutit, and calorimetric determination of the remaining glycocyamine by means of the Sakaguchi reaction. There are only two substances which are common in biological fluids and which give an intense color in the Sakaguchi reaction. These are arginine and glycocyamine. This method was first introduced by Weber (3) and was modified by Bodansky (4) and by Davenport and Fisher (5). In our hands even the latest version of the method, that described by Davenport and Fisher, had the following shortcomings: it was laborious and time-consuming, the adsorption of the glycocyamine on the Lloyd’s reagent was incomplete, further losses of glycocyamine occurred in the repeated treatment with permutit (Davenport and Fisher report losing only 10 per cent in three adsorptions; with the permutit available to us we lost 80 per cent), and the color developed was unstable. Furthermore, the amount of glycocyamine lost on the permutit varied according to the amount of arginine present, the less arginine the greater the loss of glycocyamine. All these disadvantages have been removed in the method described below. It is the first method in which glycocyamine added to blood or urine can be determined quantitatively, even in concentration8 as low a8 0.1 mg. per cent. 2 to 5 ml. are sufficient for an analysis. An indication of the speed and convenience of the method is that twenty to forty analyses can be carried through simultaneously in about 2 hours