The determination of tryptophan in plasma, liver, and urine.

Abstract A fluorometric method for the measurement of tryptophan in biological materials has been developed based on the formation of the fluorophore norharman. The sensitivity and range permit the measurement of 0.04 to 20 nmoles of tryptophan in standard 1 cm. 2 cuvettes. The standard deviation of measurement is less than 3 per cent when determining tryptophan in biological materials. The specificity of the method is such that, of the compounds tested, only tryptamine produces appreciable fluorescence: one tenth of the molar fluorescence of tryptophan. The simplicity permits 60 determinations per day. The fluorophore produced is stable in the assay solution for 1 week and all reagents used are stable for at least 2 months.