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

Abstract

In this work, an open-tubular capillary liquid-phase column was prepared by modifying chain polymer on the inner surface of capillary and chemical bonding of metal organic frameworks, NH -UiO-66, to the brushes of chain polymer (poly(glycidyl methacrylate)). Besides advantages of facial preparation and good permeability, the chain polymer effectively increases the modification amount of NH -UiO-66 nanoparticles to increase the phase ratio of open-tubular capillary column and enhance the interactions with analytes. The results of scanning electron microscope energy-dispersive X-ray spectra indicated that NH -UiO-66 nanoparticles were successfully bonded to the chain polymer. Because of the hydrophobic interaction and hydrogen bonding interaction between the analytes and the ligand of NH -UiO-66, different analytes were well separated on the NH -UiO-66-modified poly(glycidyl methacrylate) capillary (1.12 m × 25 μm id × 365 μm od) with the high absolute column efficiency reaching 121 477 plates, benefiting from an open-tubular column and low mass transfer resistance provided by polymer brush and metal-organic framework crystal. The relative standard deviations of the retention time for run-to-run, day-to-day, and column-to-column (n = 3) runs are below 4.28%, exhibiting good repeatability. Finally, the column was successfully applied to separation of flavonoids in licorice.

Open tubular liquid chromatography: Recent advances and future trends

“…Many examples of separating target compounds such as contaminant residues, phenolic, aromatic, and biological compounds using OTLC have also been recently introduced [78]. These studies explore diverse aspects of the OTLC separation approach, including the use of OT columns in different nanoLC-MS configurations [71], coating modifications [94], and the reduction of [122] the column's i.d. [132].…”

“…Cheng and collaborators [122] modified the polymeric chain of poly(glycidyl methacrylate) (pGMA) present on the inner surface of a PLOT column with MOFs (NH2-UiO-66), chemically linked in their structure for the separation of aromatic hydrocarbons, alkylbenzenes, phenols, anilines and flavonoids in licorice. This new modified phase was able to promote hydrophobic and hydrogen interactions with the analytes and covalent interactions with amino groups present in the MOF, which resulted in an efficient separation, with the OT column reaching 121 477 plates with high mass transfer and good repeatability between analyses.…”

“…Moreover, a 25 μm × 1.12 m (i.d. × length) column coated with NH 2 ‐UiO‐66‐modified poly(glycidyl methacrylate) phase was applied to the separation of benzene, naphthalene, acenaphthene, and phenanthrene in reversed‐phase separations, presenting a hydrophobic retention mechanism [122].…”

Metal-Organic Frameworks in Green Analytical Chemistry

“…In any case, the incorporation of MOFs as stationary phases in GC and LC, or as pseudo-stationary phases in capillary electro-chromatography (CEC), benefits from the low numbers of MOFs required in such phases, together with the clear reutilization of such phases. Table 3 includes a summary of representative analytical applications of MOFs when included as stationary of pseudo-stationary phases in different chromatographic techniques in the last three years [101][102][103][104][105][106][107][108][109][110][111][112][113][114][115]. Mostly, MOFs form part of composites with silica or polymers in such phases [101,102], hardly being utilized in its neat appearance.…”

“…Green aspects in these applications are from the need of low amounts of MOFs to prepare the phases (from 2 mg of H 2 N-UiO-66 [103] in a capillary column to 1.5 g of γ-CD-MOF [106] in a packed column), reutilization of the as-prepared MOF-based stationary phases, MOF design, and in some cases, even their synthesis.…”