Microdialysate analysis of monoamine neurotransmitters—A versatile and sensitive LC–MS/MS method

We have developed and validated a sensitive method for the simultaneous determination of some monoamine neurotransmitters like dopamine (DA), norepinephrine (NE) and serotonin (5-HT) in rat brain microdialysate using high-performance liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS). Sensitivity enhancement has been achieved by amine derivatization with the reagent (5-N-succinimidoxy-5-oxopentyl)triphenylphosphonium bromide (SPTPP) under mild conditions. The use of the selected reaction monitoring (SRM) mode has allowed detection of the analytes at a concentration of 30 pM (lower limit of quantification, LLOQ, signal-to-noise ratio higher than 5) with an accuracy of ≤3.80% and a precision of ±7.39 (%CV) for all neurotransmitters. Derivatization improves resolution and chromatographic retention times (3 min) by lipophilization. Linearity has been good (R > 0.99) over a large concentration range (30–50,000 pM). The intra and inter-batch accuracy and precision were not greater than 4.8% and 6.4%, respectively. Therefore, the method was successfully applied for monitoring the concentration changes of neurotransmitters in microdialysis samples deriving from striatum rat brain region after amphetamine administration (3 mg kg⁻¹, i.p.).