High performance liquid chromatographic analysis of time‐dependent changes in urinary excretion of indoleamines following tryptophan administration

Analytical conditions of prepurification extraction and HPLC separation were optimized for determination of urinary serotonin and tryptamine. Under optimal conditions, serotonin, tryptamine and an internal standard were extracted with 15% v/v n‐propanol in diethyl ether from urine samples alkalized with a phosphate buffer (0.75 mol/L, pH 10.0), and then they were re‐extracted into an HCI solution (0.1 mol/L). Purified indoleamines were simultaneously separated by reversed‐phase ion‐pair HPLC with native fluorescence detection. Urinary serotonin and tryptamine were selectively determined within about 45 min per sample for the whole procedure. Analytical recovery, reproducibility and detection sensitivity were satisfactory for pursuing time‐dependent changes in indoleamine levels. Urinary excretion profiles of serotonin and tryptamine in subjects dosed with L‐tryptophan were successfully analyzed by our method.