Abstract: A simple, rapid and sensitive method for the determination of 5-hydroxytryptamine (serotonin), 5-hydroxytryptophan or 5-hydroxyindole-3-acetic acid, using flow injection analysis with acidic potassium permanganate chemiluminescence detection, is described. The log-log plots for 5-hydroxytryptamine, 5-hydroxytryptophan and 5-hydroxyindole-3-acetic acid gave equations of best fit, of y = -0.03x2+0.51x+6.15 (r2 = 0.9990), y = -0.05x2+0.35x+5.70 (r2 = 0.9995) and y = -0.04x2+0.49x+5.60 (r2 = 0.9999), respectively., where y is log (chemiluminescence emission response (mV)) and x is log (concentration. (M)). The log-log calibration functions for the three analytes approximated linearity in the concentration. range from 1 x 10^-8 to 1 x 10^-6 M, where the slopes of the log-log plots were within the range from 1.01 to 1.04. The precision (measured as relative standard deviation) for 5-hydroxytryptamine was 2.3% (n = 6 at 1 x 10^-7 M). The detection limits (signal-to-noise ratio = 3) were 2 x 10^-9 M, 3 x 10^-9 M and 1.5 x 10^-8 M for 5-hydroxytryptamine, 5-hydroxytryptophan and 5-hydroxyindole-3-acetic acid, respectively. Preliminary experiments using an extended range photomultiplier tube realized enhanced detection limits due to the wavelength of max. emission being centered around 670 nm rather than 610 nm as previously thought. (34 References)

Abstract: Tryptophan metabolites were determined fluorimetrically after oxidation with H2O2 - CuSO4. Procedure: To a 0.5 mL portion of the sample solution was added 2.5 mL of a solution 15 mM in H2O2, 12 mM in CuSO4 and 150 mM in Na2CO3 - NaOH (pH 12.2), and the mixture was incubated at 80°C for 20 min. Detection was by fluorimetry at 385 nm (with excitation at 315 nm). A HPLC method is described for quantitative separation of kynurenine and tryptophan in serum by using H2O2 - CuSO4 as post-column derivatization reagent. 3-Hydroxykynurenine in urine was determined following reaction with H2O2 and peroxidase; detection was by fluorimetry at 520 nm (with excitation at 350 nm).

Abstract: Diffusion coefficients of 5-hydroxyindole, 5-methoxyindole, their derivatives, and ascorbic acid have been determined at 0.5 X and 5 X lo-' M by flow injection analysis. The mobile phase is a 0.1 M phosphate buffer solution at pH 7.4. Results obtained are found to correlate well with the size of the molecule and may be interpreted on the basis of the Stokes-Einstein relation.