Fluorometric determination of guanidino compounds by new postcolumn derivatization system using reversed-phase ion-pair high-performance liquid chromatography

A new postcolumn derivatization system using 1,2-naphthoquinone-4-sulfonate as fluorogenic reagent for the fluorometric determination of guanidino compounds is described. The guanidino compounds were separated by reversed-phase ion-pair high-performance liquid chromatography with an isocratic mobile phase containing the fluorogenic reagent and octane-sulfonate as the counterion. Fluorophors were derived from a condensation of guanidino compounds with the fluorogenic reagent in an alkaline solution. The chromatographic system using the mobile phase containing the fluorogenic reagent was simplified because only two pumps were required to deliver the mobile phase and the alkaline solution. Separation of guanidino compounds was completed within 25 min using a Nucleosil C8 column (5 microns, 15 cm X 4.6 mm i.d.). This method was applied to serum obtained from patients on hemodialysis therapy.