| Abstract
| - Accuracy in molecular weight determination by gel permeation chromatography (GPC) depends on the quantitative reliability of the experimental chromatogram and also on the availability of a method for estimating the retention volume-molecular weight relationship (calibration of the columns). The principal disadvantage of the refractometer, the commonly used detector for GPC, is the unwanted response to sample and eluent impurities that tend to obscure the chromatogram in the low molecular weight region. To avoid this effect, a previously described belt detector was used in these studies. Baselines showed virtually no drift; and air, water and other undesirable peaks were absent. High sensitivity and low dead volume permitted use of low polymer concentrations and columns of small cross section. However, this system did require careful control of flow rate. Data obtained with this system illustrate the calibration of the chromatographic columns as carried out in our laboratories. This calibration is based on the theory of polymer solutions. A calibration curve obtained by means of polystyrene fractions, which are commercially available, and some additional data on the unknown polymer usually suffice to establish the calibration curve for the latter, without the need for fractionation.
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