title: Determination of unbound L-tryptophan in human plasma using high-performance liquid chromatography with fluorescence detection.
abstract: An assay for the measurement of unbound L-tryptophan concentrations in plasma was developed using reverse-phase HPLC with fluorescence detection. Unbound L-tryptophan from plasma was obtained using the Amicon MPS-1 ultrafiltration device. L-tryptophan binding to the membrane in the ultrafiltration device was not significant. A linear relationship between the peak-area ratios (peak-area of L-tryptophan to internal standard) and concentrations of L-tryptophan was obtained in the range of 0.1 microgram/mL to 2.5 micrograms/mL. The intra-assay precision was less than 10% for each control (0.18 microgram/mL, 0.75 microgram/mL and 2.0 micrograms/mL). The inter-assay precision was less than 15% for each control; the accuracy for each control; the accuracy for each control, expressed as percent difference from nominal (%DFN), was less than 12%. This method was used to determine unbound L-tryptophan concentrations in plasma from nine male subjects who participated in a clinical study.
authors.affiliation: Department of Pharmacy and Pharmaceutics, Medical College of Virginia, Virginia Commonwealth University, Richmond, USA.
authors.forename: V
authors.initials: V
authors.lastname: Jagannathan
authors.forename: C
authors.initials: C
authors.lastname: March
authors.forename: J
authors.initials: J
authors.lastname: Venitz
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000008:administration & dosage; D002851:Chromatography, High Pressure Liquid; D004311:Double-Blind Method; D005615:Freezing; D006801:Humans; D008297:Male; D008567:Membranes, Artificial; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000097:blood*; D014462:Ultrafiltration
chemical_list: D000596:Amino Acids; D008567:Membranes, Artificial; D014364:Tryptophan