Preparation of an Electrochromatographic Stationary Phase Using a New Polymethacrylate Monolith with Chloropropyl Functionality

Various Strategies in Post-Polymerization Functionalization of Organic Polymer-Based Monoliths Used in Liquid Phase Separation Techniques

This review article is aimed at summarizing the various strategies that have been developed so far for post-polymerization functionalization (PPF) of organic polymer-based monoliths used in liquid phase separation techniques, namely HPLC at all scales and capillary electrochromatography (CEC). The reader will find the organic reactions performed on monolithic columns for grafting the chromatographic ligands needed for solving the separation problems on hand. This process involves therefore the fabrication of template monoliths that carry reactive functional groups to which chromatographic ligands can be covalently attached in a post-polymerization kind of approach. That is, the template monolith that has been optimized in terms of pore structure and other morphology can be readily modified and tailor made on column to fit a particular separation. The review article will not only cover the various strategies developed so far but also describe their separation applications. To the best of our knowledge, this review article will be the first of its kind.

Synthesis of a reactive polymethacrylate capillary monolith and its use as a starting material for the preparation of a stationary phase for hydrophilic interaction chromatography

Poly(3-chloro-2-hydroxypropyl methacrylate-co-ethylene dimethacrylate), poly(HPMA-Cl-co-EDMA) capillary monolith was proposed as a reactive starting material with tailoring flexibility for the preparation of monolithic stationary phases. The reactive capillary monolith was synthesized by free radical copolymerization of 3-chloro-2-hydroxypropyl methacrylate (HPMA-Cl) and ethylene dimethacrylate (EDMA). The mean pore size, the specific surface area and the permeability of poly(HPMA-Cl-co-EDMA) monoliths were controlled by adjusting porogen/monomer volume ratio, porogen composition and polymerization temperature. The porogen/monomer volume ratio was found as the most effective factor controlling the porous properties of poly(HPMA-Cl-co-EDMA) monolith. Triethanolamine (TEA-OH) functionalized polymethacrylate monoliths were prepared by using the reactive chloropropyl group of poly(HPMA-Cl-co-EDMA) monolith via one-pot and simple post-functionalization process. Poly(HPMA-Cl-co-EDMA) monolith reacted with TEA-OH was evaluated as a stationary phase in nano-hydrophilic interaction chromatography (nano-HILIC). Nucleotides, nucleosides and benzoic acid derivatives were satisfactorily separated with the plate heights up to 20μm. TEA-OH attached-poly(HPMA-Cl-co-EDMA) monolith showed a reproducible and stable retention behaviour in nano-HILIC runs. However, a decrease in the column performance (i.e. an increase in the plate height) was observed with the increasing retention factor. Hence "retention-dependent column efficiency" behaviour was shown for HILIC mode using the chromatographic data collected with the polymer based monolith synthesized.