Quantification of catecholamines in human plasma using isotope dilution mass spectrometry with para-aminobenzoic...

Measurement of low concentrations of catecholamines in biological samples remains a challenging task. In this study, a method combining magnetic solid-phase extraction (MSPE) with liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed for the stable, convenient, and effective determination of catecholamines and their derivatives in human plasma. Dopamine (DA)- and para-aminobenzoic acid (PABA)-modified magnetic nanoparticles (Fe₃O₄@PDA@PABA) were prepared as adsorbents. The established method was subjected to comprehensive methodological validation using isotope dilution mass spectrometry. The limits of detection (LOD) and lower limits of quantification (LLOQ) were in the ranges of 0.01-0.05 ng mL^-1 and 0.02-0.08 ng mL^-1, respectively. Good linearity was achieved in the ranges of 0.05-10.00 ng mL^-1 and 0.10-20.00 ng mL^-1, with correlation coefficients (R²) ranging from 0.9952 to 0.9984. The extraction recoveries in plasma were between 85.55% and 105.00%. Consequently, a hybrid method integrating MSPE and LC-MS/MS was successfully established and applied for the quantitative analysis of catecholamines and their metabolites in human plasma.