Contribution of the "Click Chemistry" Toolbox for the Design, Synthesis, and Resulting Applications of Innovative and Efficient Separative Supports: Time for Assessment

The last two decades have seen the rapid expansion of click chemistry methodology in various domains closely related to organic chemistry. It has notably been widely developed in the area of surface chemistry, mainly because of the high-yielding character of reactions of the "click" type. Especially, this powerful chemical reaction toolbox has been adapted to the preparation of stationary phases from the corresponding chromatographic supports. A plethora of selectors can thus be immobilized on either organic, inorganic, or hybrid stationary phases that can be used in different chromatographic modes. This review first highlights the few different chemical ligation strategies of the "click" type that are up to now mainly devoted to the development of functionalized supports for separation sciences. Then, it gives in a second part an up-to-date survey of the different studies dedicated to the preparation of click chemistry-based chromatographic supports while highlighting the powerful and versatile character of the "click" ligation strategy for the design, synthesis, and developments of more and more complex systems that can find promising applications in the area of analytical sciences, in domains as varied as enantioselective separation, glycomics, proteomics, genomics, metabolomics, etc.

A pH-stable, crosslinked stationary phase based on the thiol-yne reaction

Stationary phases that can withstand extremes of pH and temperature are needed to allow a single column to accommodate a wider set of solutes and separation criteria. We used a simple multi-step process using the thiol-yne reaction following the modification of the silica surface with a thiol-containing silane. The monomers 1,4-diethynylbenzene (DEB) and 1,6-hexanedithiol were used to create a crosslinked thiol-yne (CTY) stationary phase along the surface of the thiol functionalized silica. In the Tanaka test characterization, the CTY phase showed a low phase ratio, methylene selectivity typical of a reversed phase, and extremely high shape selectivity compared to commercial reversed phases. The hydrophobic subtraction model characterization showed a high positive steric resistance, a low hydrogen bond acidity, and a high cation-exchange capacity compared to most reversed phases. At pH 0.5 with an 85% aqueous mobile phase the phase showed no significant change over 114 h. With a 50% aqueous mobile phase the phase took four more days than a sterically protected C18 phase for the k' to decline 25%. At pH 12.6, 50% aqueous mobile phase, a sterically protected C18 phase showed a 20% decrease in k' and more than a 60% decrease in theoretical plates per meter in three hours. The CTY phase actually showed modest increases in k' and theoretical plates per meter after three hours.

Multi-lumen capillary based trypsin micro-reactor for the rapid digestion of proteins

In this work we evaluated a novel microreactor prepared using a surface modified, high surface-to-volume ratio multi-lumen fused silica capillary (MLC). The MLC investigated contained 126 parallel channels, each of 4 μm internal diameter. The MLC, along with conventional fused silica capillaries of 25 μm and 50 μm internal diameter, were treated by (3-aminopropyl)triethoxysilane (APTES) and then modified with gold nanoparticles, of ∼20 nm in diameter, to ultimately provide immobilisation sites for the proteolytic enzyme, trypsin. The modified capillaries and MLCs were characterised and profiled using non-invasive scanning capacitively coupled contactless conductivity detection (sC4D). The sC4D profiles confirmed a significantly higher amount of enzyme was immobilised to the MLC when compared to the fused silica capillaries, attributable to the increased surface to volume ratio. The MLC was used for dynamic protein digestion, where peptide fragments were collected and subjected to off-line chromatographic evaluation. The digestion was achieved with the MLC reactor, using a residence time of just 1.26 min, following which the HPLC peak associated with the intact protein decreased by >70%. The MLC reactors behaved similarly to the classical in vitro or in-solution approach, but provided a reduction in digestion time, and fewer peaks associated with trypsin auto-digestion, which is common using in-solution digestion. The digestion of cytochrome C using both the MLC-IMER and the in-solution approach, resulted in a sequence coverage of ∼80%. The preparation of the MLC microreactor was reproducible with <2.5% RSD between reactors (n = 3) as determined by sC4D.

Novel in-capillary polymeric monoliths arising from glycerol carbonate methacrylate for flow-through catalytic and chromatographic applications

In-capillary reactive polymer monoliths have been prepared from glycerol carbonate methacrylate functional monomer, suitably functionalized and further applied to separation science and flow-through catalysis, respectively.

Thiol–ene click chemistry for the design of diol porous monoliths with hydrophilic surface interaction ability: a capillary electrochromatography study

Thiol–ene click chemistry provides an efficient surface grafting strategy for designing diol monoliths meant for hydrophilic interaction capillary electrochromatography.