Validation of a chromatographic method to quantify tryptophan in human plasma

Abstract

The tryptophan is an essential aromatic amino acid, precursor in serotonin synthesis, one of the most important neurotransmitters of our nervous system. Therefore, tryptophan availability is the main limiting factor in serotonin synthesis. The brain serotonin concentration is directly related to the plasma and brain tryptophan concentration. Tryptophan has been the most studied biochemical marker more frequently studied by the psychiatric community, aimed at the social behavior research in both normal and pathological conditions. An HPLC reverse phase isocratic method with direct detection by fluorescence was validated in order to quantify tryptophan in human plasma samples, with the aim of estimate the tryptophan reference intervals in the laboratory and its quantification in plasma samples from schizophrenic patients. The following parameters were calculated: specificity, linearity, accuracy and precision (repeatability and intermediate precision). The method validation results are reported and prove its reliability.