Comparison of Different Techniques of Correcting for Band Broadening in GPC

A qualitative description is presented for two types of gel permeation chromatography (GPC) band broadening. One is symmetrical or Gaussian band broadening; the other is unsymmetrical or skewed band broadening. The effects of band broadening on chromatogram interpretation are discussed. Available methods of correcting the GPC molecular weight distribution (MWD) for the effects of symmetrical and unsymmetrical band broadening are discussed and compared. For symmetrical band broadening, Tung's original polynomial expansion method is generally adequate. Tung's newer methods look promising for both symmetrical and unsymmetrical band broadening, but they require further evaluation. For unsymmetrical band broadening, the method of Balke and Hamielec looks most promising for unimodal MWD's, but it requires further evaluation with more complex MWD's. Except for the latter method, the corrected MWD's for all methods had inconsistent oscillations when resolution was low or skewing was significant. Since these oscillations are prabably caused by noise in the chromatogram or inaccuracies in reading chromatogram heights, they could be minimized by improving chromatogram accuracy and by using correction techniques that include adequate data smoothing.