Separation of tryptophan metabolites by reversed-phase high-performance liquid chromatography with amperometric and fluorescence detection.

An isocratic method for the separation of most of the tryptophan metabolites in the oxidative degradation pathway is described. The chromatographic analysis utilizes the combined selectivity and sensitivity of amperometric and fluorimetric detection. The effect of pH, ionic strength and operating potential on retention times and detector responses are evaluated. The use of dual electrochemical cells at two operating potentials together with a programmable fluorescence detector allows for improved selectivity for the detection of metabolites. The sensitivity achieved with this method allows for the detection of the metabolites in biological fluids at the picomole level. The method has been used to monitor serum samples obtained during a tryptophan load test.