Post-column derivatization of guanidino compounds in high-performance liquid chromatography using ninhydrin

A new method for the high-performance liquid chromatography of guanidino compounds using ninhydrin as the fluorescence reagent is described. Use of organic solvent is not required since ninhydrin is highly soluble in aqueous media, and the problem of precipitation formation occurring in the phenanthrenequinone method was avoided. Creatine was also assayed in the present procedure. Separation of ten guanidino compounds was completed within 30 min using a small-size (38 X 4.2 mm I.D.) strong cation-exchange column.