Guanidine exhibited the highest fluorescence intensity in reaction with 9, 10-phenanthraquinone (PQ) and its intensity was about 5 times that of arginine, while the intensity of streptomycin and biguanides was less than one-half of that of arginine. The fluorometric method for the determination of guanidine was established as follows : To 0.5 ml of guanidine sample solution, 1.5 ml of 0.1 mM dimethylformamide solution of PQ and 0.25 ml of 1 M NaOH are added. After 40-50 min, 0.25 ml of conc. HCl and 2.5 ml of water are added. The fluorescence intensity of this solution is measured at 390 nm (excitation wavelength, 310 nm). Guanidine in a concentration range of 0.075 to 0.75 nmol/0.5 ml can be determined by this procedure. This method can be applied to the determination of 0.005-0.32 μmol/ml of guanidine in the presence of monosubstituted guanidines after its separation by column chromatography (weakly acidic cation-exchange resin).
