One‐pot synthesis of a new high vinyl content hybrid silica monolith dedicated to nanoliquid chromatography

Abstract

A new vinyltrimethoxysilane-based hybrid silica monolith was developed and used as a reversed-phase capillary column. The synthesis of this rich vinyl hybrid macroporous monolith, by cocondensation of vinyltrimethoxysilane with tetramethoxysilane, was investigated using an unconventional (formamide, nitric acid) porogen/catalyst system. A macroporous hybrid silica monolith with 80% in mass of vinyltrimethoxysilane in the feeding silane solution was obtained and compared to a more conventional low vinyl content hybrid monolith with only of 20% vinyltrimethoxysilane. Monoliths were characterized by scanning electron microscopy, (29) Si nuclear magnetic resonance spectroscopy and N2 adsorption-desorption. About 80% of the vinyl precursor was incorporated in the final materials, leading to 15.9 and 61.5% of Si atoms bonded to vinyl groups for 20% vinyltrimethoxysilane and 80% vinyltrimethoxysilane, respectively. The 80% vinyltrimethoxysilane monolith presents a lower surface area than 20% vinyltrimethoxysilane (159 versus 551 m(2) /g), which is nevertheless compensated by a higher vinyl surface density. Chromatographic properties were evaluated in reversed-phase mode. Plots of ln(k) versus percentage of organic modifier were used to assess the reversed-phase mechanism. Its high content of organic groups leads to high retention properties. Column efficiencies of 170 000 plates/m were measured for this 80% vinyltrimethoxysilane hybrid silica monolith. Long capillary monolithic columns (90 cm) were successfully synthesized (N = 120 000).

Advances in the development and applications of organic–silica hybrid monoliths

“…As pointed out earlier surface area measurements are carried out in a dry state but polymer monoliths tend to swell when solvated with mobile phase having small pores at the surface contributing to the column efficiency. For example, the TMOS/VTMS hybrid monoliths with surface area of only 159 m 2 /g and high density of vinyl functionalities at the pore surface achieved an efficiency of 170 000 plates/m for hexylbenzene in CLC . Epoxy‐amine based ring‐opening polymerization reaction of POSS‐epoxy with 1,4‐butanediamine resulted in homogeneous structures with surface areas below 10 m 2 /g exhibiting 169 900 plates/m for hexylbenzene in CLC and 401 500 plates/m for thiourea in CEC .…”

“…Further tuning of reaction conditions included substituting the traditional PEG porogen with formamide, and acetic acid with nitric acid, followed by modification of mixture composition (Fig. ) . Interestingly, capillaries made with larger amounts of vinyltrimethoxysilane gave lower surface areas (159 for 80% versus 551 m 2 /g for 20%) but afforded longer retention of alkylbenzenes and higher column efficiency (170 000 plates/m, H min of 5.8 μm, for hexylbenzene in CLC).…”

Synthesis of Hybrid Monolithic Columns Using a Click Chemistry Reaction for Application in Capillary Liquid Chromatography

“…This reduction results in lower consumption of mobile phase, better column performance and easier interfacing with other techniques, especially mass spectrometry (MS). 1,2 Evolving from HPLC to cLC, there are also advances in the materials used as stationary phases for capillary columns in cLC. The newest stationary phases for capillary columns are more efficient, allow higher flow rates with a minimum of increased pressure, have higher plate numbers and higher permeability, due to less mass transfer, lower pressures and higher porosities.…”

“…Among the types of click chemistry reactions, thiol-ene is the most commonly used today for obtaining monolithic materials. 2,16,20,[22][23][24][25] Zou and co-workers 16 prepared hybrid monoliths via sol-gel chemistry and the surface was tailored via a thiol-ene click reaction by using 1-octadecanethiol, sodium 3-mercapto-1-propanesulfonate and 2,2-(ethylenedioxy)diethanethiol/vinylphosphonic acid. Also, the preparation of octadecyl-functionalized and strong cation exchange (SCX) monolithic columns has been investigated for proteomic analysis in CLC-MS/MS and in SCX-reversed phase (RP)LC-MS/MS, respectively.…”

Variation in the chromatographic, material, and chemical characteristics of methacrylate‐based polymer monoliths during photoinitiated low‐temperature polymerization

“…The materials generally used to prepare monolithic beds are classified into two main categories, i.e. silica and polymer monoliths . In general, polymer monolithic columns are prepared by the in situ polymerization of a reaction solution containing a functional monomer, cross‐linker, porogenic solvents, and initiator.…”