A sensitive fluorimetric method for determination of platelet-bound and plasma free serotonin

A sensitive and specific fluorimetric assay for blood platelet-bound and plasma free serotonin is described. Serotonin is concentrated and purified on Amberlite CG-50 resin, eluted by 0.15 mol/l HCl and its native fluorescence is read at 295/350 nm. The good recovery (90% about), reproducibility and sensitivity (the smallest amount detectable is 5 ng) make the assay particularly useful for the detection of free serotonin in plasma. The whole procedure is rapid enough to permit the analysis of 15--20 samples within one working day and thus the method is suitable for routine determination of serotonin in biological specimens.