Automated mass spectrometric analysis of urinary and plasma serotonin

Serotonin emerges as crucial neurotransmitter and hormone in a growing number of different physiologic processes. Besides extensive serotonin production previously noted in patients with metastatic carcinoid tumors, serotonin now is implicated in liver cell regeneration and bone formation. The aim was to develop a rapid, sensitive, and highly selective automated on-line solid-phase extraction method coupled to high-performance liquid chromatography–tandem mass spectrometry (XLC-MS/MS) to quantify low serotonin concentrations in matrices such as platelet-poor plasma and urine. Fifty microliters plasma or 2.5 μL urine equivalent were pre-purified by automated on-line solid-phase extraction, using weak cation exchange. Chromatography of serotonin and its deuterated internal standard was performed with hydrophilic interaction chromatography. Mass spectrometric detection was operated in multiple reaction monitoring mode using a quadrupole tandem mass spectrometer with positive electrospray ionization. Serotonin concentrations were determined in platelet-poor plasma of metastatic carcinoid patients (n = 23) and healthy controls (n = 22). Urinary reference intervals were set by analyzing 24-h urine collections of 120 healthy subjects. Total run-time was 6 min. Intra- and inter-assay analytical variation were <10%. Linearity in the 0–7300 μmol/L calibration range was excellent (R2 > 0.99). Quantification limits were 30 and 0.9 nmol/L in urine and plasma, respectively. Platelet-poor serotonin concentrations in metastatic carcinoid patients were significantly higher than in controls. The urinary reference interval was 10–78 μmol/mol creatinine. Serotonin analysis with sensitive and specific XLC-MS/MS overcomes limitations of conventional HPLC. This enables accurate quantification of serotonin for both routine diagnostic procedures and research in serotonin-related disorders

A SIMPLE PAIRED-ION LIQUID-CHROMATOGRAPHY ASSAY FOR SEROTONIN IN CEREBROSPINAL-FLUID, PLATELET-RICH PLASMA, SERUM AND URINE

Anderson and co-workers1 recently described a simple high-performance liquid chromatographic/fluorimetric assay for serotonin and tryptophan, in which deproteinised samples were directly injected. Using this method routinely, we frequently observed interference which could not sufficiently be resolved from serotonin to allow accurate quantitation. However, when the amine was isolated by ion-exchange chromatography prior to HPLC separation as advocated by Koch and Kissinger,2 chromatograms were obtained with practically no extraneous peaks. In this paper the application of this method for the determination of serotonin in CSF, plasma, serum and urine is described. </jats:p