The unique properties of covalent triazine-based organic
framework/polymers, including large surface area, hydrophilic–lipophilic-balanced
adsorption, and economical preparation, make it a promising candidate
as a stationary phase for high-performance liquid chromatography.
However, irregular shapes and wide size distributions of such particles
hinder column packing, resulting in a low column efficiency or a high
back pressure. Herein, we describe the fabrication of SiO2@ covalent triazine-based organic polymer (CTP) core–shell
microspheres with a distinct sphere-coating-sphere appearance using
aminosilica as the supporting substrate to grow the CTP shell. By
adjusting the amount of reactants, the thickness of the CTP shell,
which consists of triazine and 1,3,5-triphenylbenzene monomers, was
easily controlled. The developed core–shell microspheres were
characterized via scanning electron microscopy, energy dispersive
X-ray spectroscopy, transmission electron microscopy, solid-state 13C nuclear magnetic resonance analysis, and N2 adsorption
experiments. The synergism of the triazine and aromatic moieties on
CTP provides the new stationary phase with multiple retention mechanisms,
including hydrophobic, π–π, electron donor–acceptor,
hydrogen-bonding interactions, and so forth. On the basis of these
interactions, successful separation and higher shape selectivity were
achieved among several analytes that vary in polarity under both reversed-phase
and hydrophilic interaction liquid chromatography conditions. Therefore,
SiO2@CTP microspheres combine the advantages of good column
packing properties of the uniform monodisperse silica microspheres
and the recognition performance of CTP, generating flexible selectivity
and application prospect for both hydrophilic and hydrophobic analytes.
Two versions of reversed-phase/hydrophilic interaction
mixed-mode
core–shell stationary phases for high-performance liquid chromatography
using porous organic polymers as the shell material were investigated.
The stationary phase named SiO2@CTPCC‑TPB using triazine-triphenylbenzene-based porous organic polymers as
the shell material has been reported previously. To regulate chromatographic
performance, heptazine–biphenyl moieties with fewer benzene
rings and higher nitrogen content were used as organic building blocks
to grow a porous shell on the surface of silica to acquire a core–shell
stationary phase, namely, SiO2@CHPCy‑DB. Various techniques were used to characterize the developed core–shell
microsphere, and nonpolar/polar solutes were utilized as probes to
investigate the chromatographic behavior of the stationary phase.
The results revealed that SiO2@CHPCy‑DB exhibited reversed-phase/hydrophilic interaction mixed-mode with
multiple retention mechanisms. Meanwhile, the separation behavior
of the two homemade columns and a commercial column was compared to
assess the role of the building blocks in porous organic polymers
in regulating and improving separation. The successful determination
of drugs of abuse in urine via the SiO2@CHPCy‑DB column indicated its potential for the determination of trace analytes
in complex samples.
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