Solid phase extraction and capillary electrophoretic separation of racemic catecholamines by using magnetic particles coated with a copolymer prepared from poly(3,4-dihydroxyphenylalanine) and polyethyleneimine.

Abstract

A method is presented for chiral separation of catecholamines present in bovine and mice blood. It combines magnetic solid phase extraction (MSPE) and chiral capillary electrophoresis (ch-CE). A copolymer consisting of poly(3,4-dihydroxyphenylalanine) and polyethyleneimine was coated onto magnetic particles (MPs) by co-deposition using the CuSO4/H2O2 system as a polymerization initiator. The coated MPs are spherical and the average diameter is about 168 ± 4nm. The thickness of the coating is approximately 19nm. The functional MPs are used as sorbents in MSPE to simultaneously extract the catecholamines epinephrine, norepinephrine and isoprenaline. Under the optimum conditions, the extraction efficiencies for those catecholamines are in the range from 92.3 to 98.3%, with relative standard deviations (RSDs) of <5.3%. The extraction can be performed within 4min. The extracts were then submitted to ch-CE. A method for field-enhanced sample injection (FESI) was used to enhance the detection sensitivities of the enantiomers. The limits of detection for catecholamine enantiomers range from 400 to 600pgmL-1. In comparison with the FESI-ch-CE method, the sensitivity enhancement factors of the MSPE/ch-CE method for catecholamines are about 10-fold. The method was applied to the determination of trace levels of catecholamine enantiomers in (spiked) bovine and mice blood. The recoveries ranged from 88.2 to 93.8%, with RSDs of <5.5%. The whole detection procedure takes less than 30min. Graphical abstract Schematic representation of the separation and detection of catecholamine enantiomers in blood by combination of polyDOPA/PEI-magnetic particles-based solid phase extraction and chiral-capillary electrophoresis.