Liquid chromatographic determination of free serotonin in human plasma

The complex background of interfering substances makes plasma pretreatment necessary before performing liquid-chromatographic quantitation of circulating serotonin. We compared two isolation procedures (extraction into butanol and isolation on a weak cation-exchange resin) before chromatography for measuring free serotonin from human plasma. Sensitivity, specificity and recovery were all evaluated. The cation-exchange resin yielded chromatograms with no interfering peaks, was cheaper and took less processing time than butanol extraction. We conclude that the clean-up of human plasma by a cation-exchange resin is suitable and accurate for routine liquid-chromatographic determination of circulating serotonin.