Liquid chromatography-tandem mass spectrometry assay for simultaneous quantification of catecholamines and metabolites in human plasma and cerebrospinal fluid

Catecholamines (CAs) and their metabolites in human cerebrospinal fluid (CSF) and plasma are potential biomarkers of Alzheimer's disease (AD) and facilitate early diagnosis. Liquid chromatography-tandem mass spectrometry is the gold standard method for analyzing CAs. The objective of this study was to develop and validate a liquid chromatography-tandem mass spectrometry assay capable of simultaneously quantifying dopamine (DA), epinephrine (E), norepinephrine (NE), metanephrine (MN), normetanephrine (NMN), and 3-methoxytyramine (3-MT) in both human CSF and plasma. Samples were processed by solid-phase extraction with a weak cation exchange adsorbent and then separated using an ultra-performance reversed-phase chromatography column. Analyte detection was performed using a triple quadrupole mass spectrometer operated in positive-ion multiple reaction monitoring mode. The developed assay was validated according to standard guidelines. The linearity, specificity, precision, accuracy, carryover and stability were assessed to ensure compliance with specified criteria. The lower limits of quantification for DA, E, NE, MN, NMN, and 3-MT were 4.5, 2.5, 4.5, 2.5, 2, and 0.3 pg mL^-1, respectively. The total runtime for a single sample was 6.5 min. These results demonstrated that the method was sensitive, rapid, and reliable for the simultaneous quantification of DA, E, NE, MN, NMN, and 3-MT in clinical practice. We successfully detected CAs and their metabolites in plasma and CSF samples from patients with normal cognition and AD. This study demonstrates an efficient laboratory workflow for high-throughput analysis of CAs and their metabolites and lays a foundation for further studies on AD biomarkers.