Covalent bonding of homochiral metal‐organic framework in capillaries for stereoisomer separation by capillary electrochromatography

Abstract

In this work, a [Cu(mal)(bpy)]⋅H2O (mal, L-(-)-malic acid; bpy, 4,4'-bipyridyl) homochiral metal-organic frameworks (MOFs) was synthesized and used for modifying the inner walls of capillary columns by utilizing amido bonds to form covalent links between the MOFs particles and capillary inner wall. The synthesized [Cu(mal)(bpy)]⋅H2 O and MOFs-modified capillary column were characterized by X-ray diffraction, thermogravimetric analysis, particle size distribution analysis, nitrogen absorption characterization, FTIR spectroscopy, SEM, and energy-dispersive X-ray spectroscopy (EDX). The MOFs-modified capillary column was used for the stereoisomer separation of some drugs. The LODs and LOQs of six analytes were 0.1 and 0.25 μg/mL, respectively. The linear range was 0.25-250 μg/mL for ephedrine, 0.25-250 μg/mL for pseudoephedrine, 0.25-180 μg/mL for D-penicillamine, 0.25-120 μg/mL for L-penicillamine, 0.25-180 μg/mL for D-phenylalanine, and 0.25-160 μg/mL for L-phenylalanine, all with R(2) > 0.999. Finally, the MOFs-modified capillary column was applied for the analysis of active ingredients in a real sample of the traditional Chinese medicine ephedra.

Recent advances in metal‐organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis

“…. To simplify the experimental conditions, our laboratory group has designed a novel method for modifying capillary columns with MOFs. Carboxyl groups are common in MOFs, so APTES was utilized to link the MOFs to the inner capillary walls.…”

“…SEM images of a bare column and a [Cu(mal)(bpy)]·H 2 O‐modified column: (A) bare column in lower magnification; (B) modified column in lower magnification; (C) bare column in higher magnification; and (D) modified column in higher magnification. Reprinted from with permission.…”

Recent advances in microscale separation

“…Ma et al. prepared the homochiral MOFs material [Cu(mal)(bpy)]H 2 O and used for modifying a capillary column by forming covalent bonds. The column achieved the successful separation of E‐PE and DL‐penicillamine enantiomers.…”

Open‐tubular capillary electrochromatographic determination of ten sulfonamides in tap water and milk by a metal‐organic framework‐coated capillary column

“…The coated capillary column was successively used for over 100 runs without observable changes in the separation efficiency of the chiral molecules. Our laboratory has designed a covalent bonding strategy for modifying open‐tubular capillary columns with MOFs. Carboxyl groups are common in MOFs, and thus, (3‐aminopropyl)‐ triethoxysilane (APTES) was utilized to link the MOFs to the inner capillary walls.…”