Simultaneous quantification of six monoamine neurotransmitters in biological samples by magnetic solid-phase extraction coupled with UHPLC-MS/MS using a polyethylenimine-dopamine@NH2-MIL-53(Al)-SiO2@Fe3O4 composite

Monoamine neurotransmitters play vital roles in cognitive and various physiological and pathophysiological processes, but their trace levels, small sample volumes, and complex biological matrices in biological samples pose significant analytical challenges. This study developed a novel method for the simultaneous quantification of six monoamine neurotransmitters—tyrosine, vanillylmandelic acid, tryptophan, 3,4-dihydroxyphenylacetic acid, 5-hydroxyindole-3-acetic acid, and homovanillic acid—in human serum and urine. The method utilizes magnetic solid-phase extraction coupled with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). A multifunctional magnetic composite, polyethylenimine@polymer dopamine hydrochloride@NH 2 -MIL-53(Al)-SiO 2 @Fe 3 O 4 , was synthesized, exhibiting high extraction selectivity and capacity and achieving an extraction range of 9.61–25.4 nmol/mg for the target neurotransmitters. The analytical method, optimized for the aforementioned composite, exhibited robust linearity for all six monoamine neurotransmitters, with correlation coefficients ( R 2 ) exceeding 0.998. The limits of detection (S/N = 3) ranged from 1.1 to 22 ng/L, indicating high sensitivity. Recovery rates for the targeted analytes varied between 94.5 % and 112 %, and relative standard deviations remained within the range of 1.5–9.4 %. These findings confirm that the developed methodology is sensitive, accurate, selective, and reliable for the quantitative determination of trace monoamine neurotransmitters in complex biological samples.