Liquid-chromatographic determination of serotonin in serum and plasma.

Using high-performance liquid chromatography with electrochemical detection, we determined serotonin in plasma from parkinsonian patients being treated with L-3,4-dihydroxyphenylalanine or N-(DL-seryl)-N'(2,3,4-trihydroxybenzyl)hydrochloride plus L-3,4-dihydroxyphenylalanine ("Sinemet") and in serum from a blood bank, from "normal" persons, and a pooled specimen from a hospital clinical laboratory. The values obtained for the two groups of Parkinson's disease patients showed no significant difference. Long-term storage on solid CO2 was xhown to be an adequate technique for preserving samples. The mean (+/-SEAM) normal value obtained for serotonin in serum was 146 +/- 46 microgram/liter (n = 23), a result in harmony with that previously obtained [Clin. Chem. 20, 812 (1974)] by fluorometry. In comparison to other methods for measurement of serotonin in serum or plasma, we believe that the present scheme offers greater selectivity, sensitivity, and precision.