Polymer HPLC column packing surface

The hydrophilic surface characteristics and the chemical nature of the polymer backbone in Toyopearl HW resins are the same as for packings in TSK-GEL PW HPLC columns. Consequently, Toyopearl HW packings are ideal scaleup resins for analytical separation methods developed with TSK-GEL HPLC columns. Eigure 4.44 shows a protein mixture first analyzed on TSK-GEL G3000 SWxl and TSK-GEL G3000 PWxl columns, then purified with the same mobile-phase conditions in a preparative Toyopearl HW-55 column. The elution profile and resolution remained similar from the analytical separation on the TSK-GEL G3000 PWxl column to the process-scale Toyopearl column. Scaleup from TSK-GEL PW columns can be direct and more predictable with Toyopearl HW resins. 

Phase separation (precipitation) of a polymer strongly depends on all its molecular characteristics. On the one hand, this allows very efficient separations in polymer HPLC utilizing phase separation and re-dissolution processes [20]. On the other hand, due to complexity of phase separation phenomena, the resulting retention volumes of complex polymers may simultaneously depend on several molecular characteristics of separated macromolecules. This may complicate interpretation of the separation results. Both precipitation and redissolution of most polymers is a slow process. It may be affected by the presence of otherwise inactive surface of the column packing. Therefore, the applicability and quantitative control of the phase separation phenomena may be limited to some specific systems of polymer HPLC. 

Similar to other coupled methods of polymer HPLC, for example, LC CC (Section 16.5.2), the choice of the column packing and the mobile phase components for EG-LC depends on the retention mechanism to be used. Adsorption is preferred for polar polymers applying polar column packings, usually bare silica or silica bonded with the polar groups. The eluent strength controls polymer retention (Sections 16.3.2 and 16.3.5). The enthalpic partition is the retention mechanism of choice for the non polar polymers or polymers of low polarity. In this case, similar to the phase separation mechanism, mainly the solvent quality governs the extent of retention (Sections 16.2.2, 16.3.3, and 16.3.7). It is to be reminded that even the nonpolar polymers such as poly(butadiene) may adsorb on the surface of bare silica gel from the very weak mobile phases and vice versa, the polymers of medium polarity such as poly(methyl methacrylate) can be retained from their poor solvents (eluents) due to enthalpic partition within the nonpolar alkyl-bonded phases. 

GPC is the most predictable mode of HPLC. The separation is based on the size of the sample in solution, not the molecular weight. There must not be any interaction with the column packing material (adsorption, partition, etc.), as there is in other modes of HPLC. GPC column packings are particles of cross-linked gel that contain surface pores. The sizes of these pores are controlled and vary from small to large. They act as a molecular filtration system. The most widely used gels are styrene/divinylbenzene copolymers for organic solvent-soluble polymers and acrylate gels for water-soluble polymers. 

More recently, columns have been developed where the stationary phase is formed of a porous polymer network inside the capillary. These are called monolithic phases, and have emerged as an alternative to traditional packed bed columns for use in micro-HPLC. They hold many advantages over traditional packed bed columns, being easy to manufacture since the monolith is formed in situ, often via a one-step reaction process, and its properties such as porosity, surface area, and functionality can be tailored. Another major advantage is that they eliminate the need for retaining frits. These columns can be manufactured from a variety of materials, but the most common include sol-gel, methacrylate-based, acrylamide-based, and styrene-based polymeric structures. 

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