Measurement of serotonin in platelet depleted plasma by liquid chromatography tandem mass spectrometry

5-Hydroxytryptamine (5-HT) in human platelet depleted plasma (PDP) is a biomarker in functional gastrointestinal disorders (FGID), with levels reflecting acute changes in circulating 5-HT concentration. PDP 5-HT is currently measured by reversed phase high performance liquid chromatography (HPLC) fluorimetric detection. We have developed a simple and rapid liquid chromatography tandem mass spectrometry (LC–MS/MS) method that is two times more rapid than the current HPLC methodology. Our method employs a simple protein precipitation requiring no further downstream sample preparation. 10μL of extract was injected directly onto a SecurityGuard SCX cation exchange column followed by isocratic elution onto an Onyx Monolithic C18 analytical column and methanolic gradient elution. Eluant was connected directly to a Quattro Premier XE tandem mass spectrometer operating in ES+ mode. We detected multiple reaction monitoring transitions m/z 160>114.9 and m/z 164.1>118.9 for 5-HT and d4-5-HT, respectively. 5-HT and d4-5-HT co-eluted at 2.79min and cycle time between injections was 6min. Mean recovery was 98%, limit of detection 1.5nmol/L, lower limit of quantification 5nmol/L, linearity to 1000nmol/L (r2=0.999), imprecision