A new approach to characterising carboxymethylcelluloses by size exclusion chromatography

Abstract

Sodium carboxymethylcelluloses are analysed by size exclusion chromatography using three detectors online. First, the molecular weight distribution was established using either direct molecular weight determination or the universal calibration procedure. The agreement between the two series of data is good and seems to indicate that the K and a parameters of the Mark-Houwink relationship are not strongly affected by the degree of substitution (DS) at least in the range tested. In addition, it was demonstrated that dn dc is independent of DS. The amount of salt rejected depends on the quantity of polymer injected and on its charge densities. A quantitative analysis of salt rejection was performed for three samples. The charge distribution was superimposed with the molecular weight distribution. The conductimetric detector was shown to be valuable for describing charge distributions only for low charge parameter ( λ < 1). For the three samples tested we showed that the charge density does not change with molecular weight as reflected by the constancy of the ratio between the conductimetric and refractometric signals.