Separation by Exclusion

Elution volumes in ideal SEC are limited to a narrow range (smaller than the column volume). It is clear, that no fraction of the sample can be eluted, before the interstitial volume Vi (i.e. the volume of the solvent outside the particles of the column packing) has passed the column.

• Large molecules, which have no access to the pores (exclusion limit), are eluted at Vi.

• Small molecules, which have access to the entire pore volume Vp, will appear at the void volume V0, which is the sum of the interstitial volume Vi and the pore volume Vp.

• Molecules of a size between these extremes have access only to a part of the pore volume, hence they will be eluted with an elution volume Ve between Vi and V0, which is determined by KSEC, the equilibrium constant of a sample in ideal size exclusion chromatography:

Obviously, elution volumes in ideal SEC are always smaller than the void volume of the column:

The relation between Ve and the molar mass of a polymer is determined by calibration, as will be discussed later.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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