Column packings pore size

The linear MW calibration curve of the bimodal columns, as shown in Figure 1, is the result, of proper matching of the column packing pore size -, and such a matching of pore size is relatively easy to accomplish in practice. li) Th linear MW calibration can be expressed by equation 4 ... 

Hence retention volume can be expressed in terms of two measurable quantities Fq and Ft, and Ksec which is a function of solute molecular size and of the column packing pore size. In SEC, it can only vary between zero (total exclusion) and unity (total permeation). 

The role of column packing pore size in liquid chromatography at the critical adsorption point was investigating using three silica gels and a series of polymethyl methacrylates (PMMA), using toluene, tetrahydrofuran (THF) or their mixtures as eluents. 

Equations (18) and (19) are in agreement with the experimental observations that in SEC does exist a distinctive relation between effective sizes of column packing pores and polymer coils. 

To ensure that a representative molecular-weight distribution is obtained, it is critical to choose the correct columns. This refers to the correct packing pore sizes to maximize the resolution in the molecular-weight range of concern. The solvent must also be considered. GPC is a separation technique based on the size of the polymer in solution, and the solvent will influence the conformation of the polymer in solution. The solvents that are most suitable for specific polymers are fisted in the Appendix. 

Two classes of micron-sized stationary phases have been encountered in this section silica particles and cross-linked polymer resin beads. Both materials are porous, with pore sizes ranging from approximately 50 to 4000 A for silica particles and from 50 to 1,000,000 A for divinylbenzene cross-linked polystyrene resins. In size-exclusion chromatography, also called molecular-exclusion or gel-permeation chromatography, separation is based on the solute s ability to enter into the pores of the column packing. Smaller solutes spend proportionally more time within the pores and, consequently, take longer to elute from the column. 

Based on the requirements of the separation, media of suitable pore size, particle size, and surface properties are selected as well as column dimensions and column material. In some cases a suitable combination of media type and column dimensions may be available as a prepacked column. In most cases, this is a more expensive alternative to preparing the column yourself but will provide a consistent quality as assured by the manufacturing and testing procedures of the vendor. The consistent quality may be critical in obtaining reproducible results and may thus be a cost-effective solution. Also, the fact that smaller particle-sized media are more difficult to pack and require special, and expensive, equipment has resulted in that gel filtration media of small particle size, e.g. smaller than 15 /zm, are predominantly supplied as prepacked columns. 

Select the appropriate chromatographic column or columns. Choose a column packing with a pore size that will resolve the molecular size range of the sample. 

Zorbax PSM Bimodal and Trimodal columns are packed with mixed pore-size packing to achieve linear size separations over a broad molecular weight range (Table 3.3). Zorbax PSM Bimodal columns are packed with PSM 60 and PSM 1000 particles, and Trimodal columns contain PSM 60, PSM 300, and PSM 3000 particles (Fig. 3.4). Carefully selecting and mixing different pore-size particles in columns provide much better linearity than coupling columns that are each packed with single pore-size particles. 

The different pore sizes and exclusion limits of each TSK-GEL SW column will have a substantial effect on the resolution of a biomolecule mixture. G2000SW packing, which has the smallest pores, provides the best resolution for smaller proteins such as myoglobin and cytochrome c (16,900 and 12,400 Da, respectively, Rs = 1.01). Resolution of the proteins myoglobin... 

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