The characteristics of open-tubular capillary electrochromatography columns with series/mixed stationary phases constructed with magnetic nanoparticle coating.

Novel open-tubular capillary electrochromatography (OT-CEC) systems with core/shell magnetic nanoparticles modified by amino or C18 groups as stationary phase were constructed by immobilizing nanoparticles in the capillary with permanent magnets. Influence of preparation method of OT-CEC column with series stationary phases (continuous two-dimension) on column performance and effect of dispersant on capability of OT-CEC column prepared by stationary phases with mixed functionalities (mixed stationary phases) were investigated in details to achieve stable preparation. Organic acids were used to evaluate the OT-CEC systems, and the relative column efficiency of salicylic acid was 420,000 plates/m for series stationary phases, while that of benzoic acid reached 480,000 plates/m for mixed stationary phases. The excellent within-column and between-column repeatability (n=5) testified with the RSDs of retention time were less than 0.44% and 10.20% for series stationary phases and 1.65% and 4.29% for mixed stationary phases. The two OT-CEC systems were further applied to separation of the aqueous extract of Rhizoma gastrodiae. Comparing with normal OT capillary column, the new systems show extra high column efficiency due to large surface areas of nanoparticles and multiple separation mechanisms, and they have great potential in the method development for the analysis of complicated samples.