Characterization of chitosan by steric exclusion chromatography

In this paper, the gel permeation chromatography of chitosan with different degrees of acetylation (0<DA<60 mol%) was analyzed using cationic porous supports in acidic conditions. A light scattering detector allowed the determination of the molecular weight distribution and the variation of the radius of gyration as a function of the molecular weight. From these data, the persistence length (Lp) of chitosan as a function of DA is discussed; the role of the method of preparation of the samples is also pointed out. For heterogeneously acetylated chitosan, Lp=110 Å is found to be independent on DA in the range 0<DA<25 mol%. For homogeneously reacetylated samples, Lp increases slightly from 110 to 150 Å when DA increases up to 60%. These conclusions may be related with the acetyl group distribution along the chains as examined by NMR.