A versatile method for the reliable determination of polysaccharides (inulin, polyfructans, starch) as non-structural carbohydrates (NSC), in plant samples
Apart from ordinary carbohydrates and sugar alcohols, polysaccharides, such as inulin, polyfructans and starch, are important plant components the composition of which may markedly vary with season, light availability and status of plant growth. Carbohydrate distribution also reflects changes of photosynthetic activity and abiotic stress phenomena, such as drought. In addition to plant physiology, the exact identification and reliable quantification of both polysaccharides and carbohydrates in plant material is of growing importance for the calculation of more sophisticated carbon balances of numerous biogeochemical processes. In this article, a method for the exact determination of polysaccharides of both the starch- and fructan-type is presented. The polysaccharides are split into their monomers by acidic hydrolysis. Whereas hydrolysis of polysaccharides of the fructan-type is carried out under relatively mild conditions using 1% HCl, much harsher conditions are needed for hydrolysis of starch where 30% HClO4 is applied. The hydrolysates are properly diluted and analyzed by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) for the monomers which are fructose and glucose in case of polyfructans and glucose in case of starch. A highlight of the method is its versatility: the analytical conditions used for the analysis of the polysaccharide hydrolysates are the same as for the carbohydrates and sugar alcohols. Moreover, our method has recently been successfully extended to the quantification of hydroxyethyl starch (HES) in blood plasma
