Whole blood serotonin and plasma tryptophan using high-pressure liquid chromatography with electrochemical detection.

Methods are detailed for whole blood serotonin (5-HT), equivalent to platelet 5-HT, and plasma tryptophan. These assays may be carried out on the same blood sample which need be no more than 1 ml, are rapid, and avoid the difficulties, such as protein precipitation and fluorophor formation, encountered in other methods. The linearity of the methods is extensive and allows for accurate measurement of low concentrations. Data are given for normal humans and for patients receiving psychiatric treatment for depression.