Abstract
A new colorimetric method for the determination of non-and mono-substituted guanidine compounds was established, by using 0.04% 9, 10-phenanthraquinone in dioxane-EtOH (1 : 4) and 2% 3, 5-dihydroxybenzoic acid in EtOH with the addition of 2 N KOH aqueous solution, and measuring the absorbance at 615 nm. The color intensity becomes constant after standing for 90 min in the case of guanidine, and for more than 100 min in the case of mono-substituted guanidine at room temperature. This method is recommended for the determination of non-and mono-substituted guanidines. Beer's law holds in the range of 2.5×10-3 to 6×10-2 μmol/ml in the final solution of various guanidine compounds such as salts of guanidine (25-28), glycocyamine (32), agmatine (33), and arginine (34). Guanidines with a large substituent or with an electronegative group, showed less color intensity than methylguanidine (29), or did not show any coloration. On the other hand, 1-naphthol method can be used only for the detection of monosubstituted guanidines. Limit of identification of these compounds was in the range from 0.3 to 2 μg.
