High-performance liquid chromatographic measurement of tryptophan in blood, tissues, urine, and foodstuffs with electrochemical and fluorometric detections.

A rapid and convenient measurement of tryptophan in whole blood, serum, liver, brain, urine, and alkaline hydrolysates of proteins and foodstuff was done by high-performance liquid chromatography. The sample preparation was simply homogenized or mixed in a 5% trichloroacetic acid solution and a sample of the supernatant was injected onto a column after filtration with a 0.45-micron filter. The method used a Chemcosorb 5-ODS-H column (particle size, 5 microns, 150 x 4.6 mm i.d.) eluted with 20 mM potassium dihydrogen phosphate (pH adjusted to 3.7 by the addition of phosphoric acid) containing 1 g/l of sodium heptane sulfonate and 3 mg/l EDTA.2Na-acetonitrile (93:7, v/v) at a flow rate of 1.5 ml/min. The tryptophan contents in whole blood, serum, liver, and brain were electrochemically estimated at +1000 mV vs. Ag/AgCl, the detection limit being 0.2 pmol (40.84 pg) at a signal-to-noise ratio of 5:1. The tryptophan contents in urine, proteins, and foodstuff were fluorometrically estimated with an excitation wavelength of 280 nm and with an emission wavelength of 340 nm, the detection limit being 20 pmol (4.08 ng) at a signal-to-noise ratio of 5:1. Tryptophan was eluted at about 10.5 min. The total analysis time was about 12 min.