Allowance for polydispersity in the determination of the true plate height in GPC
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In gel permeation chromatography (GPC), dispersion of a sharply injected sample arises both from the polydispersity, P, of the polmer sample and from the kinetic processes occurring within the column. The latter are described by the true plate height, H. It is shown that a current formula for deriving H from the observed band dispersion and the polydispersity is incorrect and that for samples with P≤1.1 a good approximation is H=Happ-L(P-1) (1+α)/x2 where Happ is the apparent plate height calculated in the normal way from the experimental peak width and retention time or volume; L is the column length; α is a correction term whose value is 0.4 for P=1.10; x is a measure of the relative molecular mass range covered by the packing material (x generally lies between 4 and 12 for GPC materials of narrow pore size distribution). It is concluded that the true plate height cannot generally be obtained from the elution peak of a polymer standard whose polydispersity is much larger than about 1.01.
KeywordsMolecular Mass Pore Size Distribution Mass Range Correction Term Peak Width
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