Patent ID: 8652334

Claim:
A process for separating polydisperse ionically charged polysaccharide into fractions of different average molecular weight which process comprises washing a column of ion-exchange resin to which an aqueous solution of polydisperse polysaccharides has been applied sequentially with at least three elution buffers, each having different and constant ionic strength and/or pH, wherein the second and subsequent elution buffers have higher ionic strength and/or pH than the elution buffers of the immediately preceding step, to obtain fractions whereby said polydisperse polysaccharides are separated into fractions of different average molecular weight, wherein each fraction contains fractionated polysaccharide consisting of a molecular weight polydispersity of 1.1 or lower, wherein the fractionated polysaccharide has a degree of polymerization (DP) of 10 or more and is (i) a sialic acid polymer, (ii) a sialic acid copolymer, (iii) a hydrolysed product of (i) or (ii), or (iv) a functionalised derivative of (i), (ii) or (iii).