Optimization of single-quadrupole mass spectrometry for neurometabolomics: Neurotransmitter and metabolite detection with proof-of-concept in an ant model

Single-quadrupole mass spectrometry remains an underexploited yet highly accessible option for neurochemical analysis. In this study, an analytical workflow was optimized to enhance the sensitivity of a single-quadrupole instrument operated in Selected Ion Monitoring (SIM) mode for the targeted detection of 17 neurotransmitters and related metabolites. Systematic optimization of in-source dissociation, ionization mode, and source parameters enabled substantial signal gains, particularly under HILIC conditions, where intensity increases reached up to 40-fold for highly polar analytes. The optimized method yielded sub-nanomolar detection limits for most compounds, with limits of detection in the picogram range for several neuroactive molecules, for instance 40 pg and 1 pg/injection for dopamine and octopamine respectively. Fragment-ion-based discrimination allowed reliable differentiation of structural isomers, such as dopamine and octopamine, despite their identical precursor m / z . A proof-of-concept application was conducted on dissected ant brains, demonstrating that extremely small tissue samples can be quantitatively profiled for multiple biogenic amines using only a single-quadrupole detector. Although this instrumentation does not permit global metabolite coverage, the results show that, when properly optimized, it provides sufficient sensitivity and selectivity for targeted neurochemical analysis and approaches toward neurometabolomics. The approach thus offers a cost-effective alternative for laboratories lacking tandem MS systems and can be readily adapted to other species or biological matrices. • Single-quadrupole MS optimized for targeted neurometabolomics in SIM mode. • HILIC increased sensitivity vs C18 for polar analytes (up to 40-fold). • Picogram-level detection of neurotransmitters achieved without MS/MS. • Fragment-ion SIM discriminated dopamine and octopamine structural isomers. • Method enabled quantitative profiling of biogenic amines in single ant brains.