A novel in situ strategy for the preparation of a ß-cyclodextrin/polydopamine-coated capillary column for capillary electrochromatography enantioseparations.

Inspired by the chiral recognition ability of ß-cyclodextrin and the natural adhesive properties of polydopamine under alkaline conditions, in this study, a rapid and in situ modification strategy was developed to fabricate ß-cyclodextrin/polydopamine composite material coated-capillary columns for open tubular capillary electrochromatography. The results of scanning electron microscopy, FTIR spectroscopy, streaming potential, and electro-osmotic flow studies indicated that ß-cyclodextrin/polydopamine was successfully fixed on the inner wall of the capillary column. This coating can be achieved within 1 h affording a greatly reduced capillary preparation time. The performance of the ß-cyclodextrin/polydopamine-coated capillary was validated by the analysis of seven pairs of chiral analytes, namely epinephrine, norepinephrine, isoprenaline, terbutaline, verapamil, tryptophane, carvedilol. Good enantioseparation efficiencies were achieved for all. For three consecutive runs, the relative standard deviations for the migration times of the analytes for intraday, interday, and column-to-column repeatability were in the range of 0.41-1.74, 1.03-4.18, and 1.66-8.24%, respectively. Moreover, the separation efficiency of the ß-cyclodextrin/polydopamine-coated capillary column did not decrease obviously over 90 runs. The strategy should also be feasible to introduce and immobilize other chiral selectors on the inner walls surface of capillary columns.

The preparation of poly-levodopa coated capillary column for capillary electrochromatography enantioseparation.

Levodopa (L-DOPA) is promising as chiral stationary phase for open tubular capillary electrochromatography (OT-CEC) enantioseparation owing to its self-polymerization adhesive property and chiral recognition potential. In this work, CuSO4/H2O2 was used as a trigger agent to accelerate the polymerization process of L-DOPA and the poly-levodopa (poly-(L-DOPA)) coated column was successfully prepared for the first time by depositing it on the inner wall of fused silica capillary via the rapid and in-situ approach at room temperature. The performance of the poly-(L-DOPA) coated capillary was validated by the separation of different chiral analytes, including chiral amine drugs, neurotransmitters and amino acids, and the good enantioseparation efficiencies were achieved. For five consecutive runs, the relative standard deviations (RSDs) for the migration time of the analytes for intra-day, inter-day and column-to-column were in the range of 0.19-1.33%, 0.96-4.47%, and 2.21-7.79%, respectively. Additionally, the poly-(L-DOPA) coated capillary column could be successively used over 250 runs without observable change in the separation efficiency.

Simultaneous separation of neutral and cationic analytes by one dimensional open tubular capillary electrochromatography using zeolitic imidazolate framework-8 as stationary phase.

Developing simple methods for separation of analytes that belong to different classes is of great importance. Herein, we developed a simple one-dimensional (1-D) capillary electrochromatography method to demonstrate the simultaneous separation of target fractions that belong to two different classes (i.e., cationic and neutral analytes) without switching buffer solution by a zeolitic imidazolate framework ZIF-8 coated capillary column. Owing to the difference of charge-to-mass ratio of the cationic analytes, the interaction of the cationic analytes and coating material ZIF-8 and the hydrophobic interactions between the neutral analytes and the microporous framework of ZIF-8, six cationic analytes and four neutral analytes were simultaneously separated in a single run by 1-D capillary electrochromatography. The relative standard deviations (RSDs) of the analytes migration time for intra-day, inter-day and column-to-column were in the range of 0.11-0.87%, 0.54-2.04% and 2.00-6.89% and the RSDs of the analytes peak area for intra-day, inter-day and column-to-column were in the range of 0.70-4.45%, 1.33-6.20% and 2.27-11.88%. Additionally, the developed method was employed in the analysis of urine samples with satisfactory recoveries.