Development of a nano-electrospray MSn method for the analysis of serotonin and related compounds in urine using a LTQ-orbitrap mass spectrometer

Good linear calibrations were obtained for analytes in urine (with serotonin and dopamine giving R2 = 0.9999 and 5-HIAA having a lower R2 value of 0.9955). Acceptable intraday repeatability was achieved for all analytes with RSD values (n = 5) ranging from 4.4% to 6.2% (57, 65 and 52 nmol/L for serotonin, dopamine and 5-HIAA respectively) to 2.1-8.1% (2837, 3268, 2618 nmol/L for serotonin, dopamine and 5-HIAA respectively). Excellent limits of detection (LOD) and limits of quantitation (LOQ) were achieved with spiked samples for all compounds; with LODs of 9-12.9 nmol/L and LOQs of 27.2-57.7 nmol/L for analytes in urine. An appropriate sample clean-up procedure for urine was developed to ensure highest recovery and reproducibility on analysis.