Size exclusion chromatography principles

The evolution of media covering aqueous and nonaqueous systems on the one hand and analytical as well as microscale and macroscale preparative applications on the other hand has resulted in an arbitrarily nomenclature within the field. Thus the current practice is to refer to the separation principle based on solute size as size exclusion chromatography (SEC) whereas the application in aqueous systems is traditionally referred to as gel filtration (GF) and the application in nonaqueous systems is designated gel-permeation... 

Figure 13.2. Illustration of molecular separation according to their size in a size-exclusion chromatography (SEC) column. The underlying principle of SEC is that particles of different size will elute through a stationary phase at different rates Larger molecules will take less time (or elution volume) to reach outlet of the column as compared to the smaller ones.The prerequisite of a direct correlation between elution time and molecular size is an absence of interactions between the stationary phase and an analyte. Otherwise, nonexclusion effects such as electrostatic repulsion or sorption must be considered.

This simple exercise demonstrates the chromatographic separation of the components of a mixture by a procedure that relies on two of the principles discussed above, namely ion-exchange chromatography and size-exclusion chromatography. The components to be separated (see Table 2-3) differ greatly from one another both in their molecular... 

Figure 7.4 Diagram illustrating the (a) general principles and (b) methodology of size-exclusion chromatography. (Sources (a) Adapted from Sheehan, Physical Biochemistry, 2000 (b) From Voet, Voet Pratt Fundamentals of Biochemistry, 2nd edn, 2006 Voet, Voet Pratt reprinted with permission of John Wiley Sons, Inc.)...

Size-exclusion chromatography (SEC) is the premier polymer characterization method for determining MWDs. As discussed in this volume and summarized in the following section, by hyphenating SEC with selective detectors, one can, in principle, completely characterize a polymer in terms of its molecular parameters and chemical composition in the time it takes to do a typical SEC analysis. 

Gel permeation chromatography (GPC), sometimes called size-exclusion chromatography (SEC), is based on a very simple principle a gel is constructed with a narrow range of pore sizes and packed into a chromatography column. If a polymer of infinite molecular weight is applied at the top of the column, it cannot fit into any of the pores and is eluted in volume Vq, the excluded volume. A small molecule, on the other hand, can fit into all the pores and is this eluted in volume Ft, the total volume of the column. Fractionation according to molecular size thus occurs between elution volumes Fq and Ft with molecules eluted in order of decreasing size. 

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