Total exclusion volume

What is the total exclusion volume for the column (i.e. the interstitial volume), and what is the volume of the pores (the intraparticle volume) ... 

Interparticle volume could be measured using GPC as the total exclusion volume of high-molecular-weight polymers, and the void volume could be accurately measured as the elution volume of deuterated acetonitrile eluted with neat acetonitrile. The example of these measurements and comparison with the adsorbent mass determined by unpacking the column and weighing the dried adsorbent are shown in Table 3-5. 

Molecules larger than the pore size do not enter the pores and elute together as the first peak in the chromatogram and this is called total exclusion volume which defines the exclusion limit for a particular column. Molecules that can enter the pores diffuse into the internal pore structure of the gel to an extent depending on their size and the pore size distribution of the... 

Obviously, all molecules that are not able to penetrate into the pore space, move with the same velocity. Retention volume of all these molecules is the same and is called exclusion volume, also known as total exclusion. The total exclusion volume is a characteristic of a particular column which determines its upper separation limit. 

One of the most serious disadvantages of SEC is limited peak capacity that is, only a few separated bands can be accommodated within the total chromatogram, as all peaks must elute between the total exclusion volume and the total permeation volume. 

With all these precautions and when using modem columns, it clearly appears that peaks are not Gaussian, but systematically skewed. New computing facilities allow one to analyze more precisely such peaks by various functions. The best results seems to be obtained by exponentially modified gaussian (EMG) functions, which are the convolution of a Gaussian dispersion and an exponential decay. In that case, two parameters define the shape of the peak s and t, which allow quantitative mapping of BB characteristics for further correction. Generally, a and r are constant or admit a limited increase with MW for samples eluted well after the void volume. However, a dramatic increase of a and T occurs near the total exclusion volume. ... 

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