Polysaccharides are complex polymers constructed from sugar units. There is a wide range of polysaccharides, many of which show large structural differences due to the manner in which they are synthesized. This is most commonly seen in the presence of branches on the polymer chains of some polysaccharides, which strongly influences properties such as solution viscosity. Pullulan polysaccharide is composed of maltotriose units in the polymer backbone, produced from starch by the action of a fungus. Pullulan has a linear structure, whereas in contrast dextran is a complex glucan with many differing components manufactured from sucrose by bacterial action that has a highly branched structure. Investigating the structure of polysaccharides is of interest for determining their properties in applications such as their use as food additives. Gel permeation chromatography (GPC) is a well-known technique for assessing the molecular weight distribution of polymers, a property that influences many of the physical characteristics of these materials. GPC viscometry, employing a viscometer in combination with a differential refractive index detector, has the advantage of allowing the accurate determination of molecular weights for structurally complex polymers and co-polymers regardless of the their structure, via the Universal Calibration approach. GPC viscometry also reveals information about the solution viscosity of polymers, a property related to molecular size. Using this information, the branched structure of polymers can be investigated. This application note describes the analysis of two samples of polysaccharide by GPC viscometry, pullulan with a linear structure, and a highly branched dextran. Agilent 1260 Infinity II 液相色譜系統(tǒng)