Selective enrichment of catecholamines using iron oxide nanoparticles followed by CE with UV detection

This study examines the use of unmodified magnetite nanoparticles (Fe3O4 NPs) for selective extraction and enrichment of the catecholamines dopamine (DA), noradrenaline (NE), and adrenaline (E), prior to analysis using capillary electrophoresis with UV detection. Coordination between Fe3+ on-the-surface Fe3O4 NPs and the catechol moiety of catecholamines enables Fe3O4 NPs to capture catecholamines from an aqueous solution. We obtained maximum loading of catecholamines on the NP surface by adjusting the pH of the solution to 7.0. In addition, catecholamine loading on the Fe3O4 NPs increased in conjunction with NP concentrations. H3PO4 was found to be efficient for the removal of adsorbed catecholamines on the NP surface. Adding 1.2% poly(diallyldimethylammonium chloride) to the background electrolyte resulted in a baseline separation of the liberated catecholamines within 20 min. Under optimal extraction and separation conditions, the limit of detections at a S/N ratio of 3 for E, NE, and DA were 9, 8, and 10 nM, respectively. Significantly, the combination of a phenylboronate-containing spin column and the proposed method was successfully applied to the determination of NE and DA in human urine and NE in Portulaca oleracea L. leaves.