Mixed-mode reversed-phase and ion-exchange monolithic columns for micro-HPLC

Methacrylate Polymer Monoliths for Separation Applications

This review summarizes the development of methacrylate-based polymer monoliths for separation science applications. An introduction to monoliths is presented, followed by the preparation methods and characteristics specific to methacrylate monoliths. Both traditional chemical based syntheses and emerging additive manufacturing methods are presented along with an analysis of the different types of functional groups, which have been utilized with methacrylate monoliths. The role of methacrylate based porous materials in separation science in industrially important chemical and biological separations are discussed, with particular attention given to the most recent developments and challenges associated with these materials. While these monoliths have been shown to be useful for a wide variety of applications, there is still scope for exerting better control over the porous architectures and chemistries obtained from the different fabrication routes. Conclusions regarding this previous work are drawn and an outlook towards future challenges and potential developments in this vibrant research area are presented. Discussed in particular are the potential of additive manufacturing for the preparation of monolithic structures with pre-defined multi-scale porous morphologies and for the optimization of surface reactive chemistries.

Synthesis and characterization of a multimode stationary phase: Congo red derivatized silica in nano-flow HPLC

Congo red derivatized silica has been developed as a mixed mode stationary phase and used for nano-flow HPLC.

Phosphatidic acid-functionalized monolithic stationary phase for reversed-phase/cation-exchange mixed mode chromatography

A reversed-phase and cation-exchange mixed-mode poly(MDPA-co-EDMA) monolith was successfully prepared and applied to the separation of a wide range of analytes, such as small peptides, phenols, vitamins B, pharmaceutical compounds.

Quest for organic polymer-based monolithic columns affording enhanced efficiency in high performance liquid chromatography separations of small molecules in isocratic mode

The separations of small molecules using columns containing porous polymer monoliths invented two decades ago went a long way from the very modest beginnings to the current capillary columns with efficiencies approaching those featured by their silica-based counterparts. This review article presents a variety of techniques that have been used to form capillary formats of monolithic columns with enhanced separation performance in isocratic elutions. The following text first describes the traditional approaches used for the preparation of efficient monoliths comprising variations in polymerization conditions including temperature as well as composition of monomers and porogenic solvents. Encouraging results of these experiments fueled research of completely new preparation methods such as polymerization to an incomplete conversion, use of single crosslinker, hypercrosslinking, and incorporation of carbon nanotubes that are described in the second part of the text.

Porous polymer monoliths: amazingly wide variety of techniques enabling their preparation

The porous polymer monoliths went a long way since their invention two decades ago. While the first studies applied the traditional polymerization processes at that time well established for the preparation of polymer particles, creativity of scientists interested in the monolithic structures has later led to the use of numerous less common techniques. This review article presents vast variety of methods that have meanwhile emerged. The text first briefly describes the early approaches used for the preparation of monoliths comprising standard free radical polymerizations and includes their development up to present days. Specific attention is paid to the effects of process variables on the formation of both porous structure and pore surface chemistry. Specific attention is also devoted to the use of photopolymerization. Then, several less common free radical polymerization techniques are presented in more detail such as those initiated by gamma-rays and electron beam, the preparation of monoliths from high internal phase emulsions, and cryogels. Living processes including stable free radicals, atom transfer radical polymerization, and ring-opening metathesis polymerization are also discussed. The review ends with description of preparation methods based on polycondensation and polyaddition reactions as well as on precipitation of preformed polymers affording the monolithic materials.