In Situ Synthesis of MIL-100(Fe) in the Capillary Column for Capillary Electrochromatographic Separation of Small Organic Molecules

Abstract

Because of the unusual properties of the structure, the metal organic frameworks (MOFs) have received great interest in separation science. However, the most existing methods for the applications of MOFs in separation science require an off-line procedure to prepare the materials. Here, we report an in situ, layer-by-layer self-assembly approach to fabricate MIL-100(Fe) coated open tubular (OT) capillary columns for capillary electrochromatography. By a controllable manner, the OT capillary columns with a tailored MIL-100(Fe) coating have been successfully synthesized. The results of SEM, XRD, FT-IR, and ICP-AES indicated that MIL-100(Fe) was successfully grafted on the inner wall of the capillary. Some neutral, acidic and basic analytes were used to evaluate the performance of the MIL-100(Fe) coating OT capillary column. Because of the size selectivity of lattice aperture and hydrophobicity of the organic ligands, three types of analytes were well separated with this novel MIL-100(Fe) coating OT capillary column. For three consecutive runs, the intraday relative standard deviations (RSDs) of migration time and peak areas were 0.4-4.6% and 1.2-6.6%, respectively. The interday RSDs of migration time and peak areas were 0.6-8.0% and 2.2-9.5%, respectively. The column-to-column reproducibility of retention time was in range of 0.6-9.2%. Additionally, the 10 cycles OT capillary column (10-LC) could be used for more than 150 runs with no observable changes on the separation efficiency.

Recent applications of nanomaterials in capillary electrophoresis

“…Xu et al. also developed an in situ layer‐by‐layer self‐assembly approach to fabricate MIL‐100(Fe) coated capillary columns for the separation of aromatic acids and anilines and homochiral MOF AlaZnCl coated capillary columns for enantioseparation of four monoamine neurotransmitters and two amine drugs . Subsequently, the same group developed an even simpler and faster manufacturing method in order to improve reproducibility and to expand the application of MOF OT‐CEC columns .…”

“…This method consisted in the use of ZnO NPs as nucleating in the preparation of homochiral MOF [Zn(s‐nip) 2 ] n to reduce considerably the synthesis time. In comparison with the previous works in which not less than 15 h were necessary , this method was carried out in 5 h. The synthesized column was applied to the enantioseparation of epinephrine, isoprenaline and synephrine enantiomers and the isomers of nitrophenols and analogs of bisphenols, obtaining moderate resolution and efficiency and well stability and reproducibility. Finally, the enantioseparation performance of the [Zn(s‐nip) 2 ] n coated OT column using ZnO NPs as nucleating agent was compared with the [Zn(s‐nip) 2 ] n coated OT columns fabricated by the layer‐by‐layer self‐assembly and the off‐line methods.…”

Open tubular‐capillary electrochromatography: Developments and applications from 2013 to 2015

“…Figure shows the method of Xu et al. for the preparation of an innovative class of iron(III) carboxylate MOF‐coated capillaries. This procedure involved chemically modifying the bare silica surface with 3‐glycidoxypropyltrimethoxysilane‐iminodiacetic acid‐silane and the layer‐by‐layer assembly by alternate infusion of solutions of FeCl 3 ·6H 2 O and 1,3,5‐benzenetricarboxylic acid/ethanol.…”

“… and Xu et al. achieved separations of small molecules using MOFs with the aromatic framework of 1,3,5‐benzenetricarboxylic acid, while Tiala and coworkers have separated steroids using phospholipid vesicles . Other interesting work, carried out by Zhang and coworkers, describe the use of a reversed‐phase‐like separation of benzene derivatives using hydroxyapatite with a polydopamine coating .…”

Preparation and evaluation of open‐tubular capillary column combining a metal–organic framework and a brush‐shaped polymer for liquid chromatography

“…Xu et al. used layer‐by‐layer approach to fabricate MIL‐100(Fe) coated open tubular capillary to separate neutral, acidic, and basic analytes in CEC mode .…”