This study describes a versatile and validated method for the analysis of these three compounds in urine using a nanoelectrospray-MSn method interfaced with an LTQ Orbitrap mass spectrometer. No chromatographic separation is required prior to nanoelectrospray infusion.
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.