[Fluorometric determination of free and total tryptophan in blood plasma]

Free and total tryptophan is estimated in the plasma by a spectrofluorimetric method using an amplification reaction and fluorescence by transformation of tryptophan into norharman using formalin and perhydrol (fluorescence is amplified about 15 times). Free tryptophan in the plasma is separated by ultrafiltration under pressure. We verified the analytical characteristics of the method in order to obtain optimal conditions. Values frequently found in 16 blood donors in good health were 10.4 +/- 3.3 micronmol/l. for free tryptophan (average +/- ts for a risk of 5%) and 54.6 +/- 18.6 micronmol/l. for total tryptophan.