Determination of Single Sugars, Including Inulin, in Plants and Feed Materials by High-Performance Liquid Chromatography and Refraction Index Detection

Abstract

The exact and reliable detection of sugar monomers and fructans provides important information for the evaluation of carbohydrate metabolism in plants and animals. Using the HPLC method; a large number of samples and single sugars; with both high sensitivity and selectivity; may be analysed. It was shown that the described method—using a Nucleosil column loaded with Pb2+ ions; a refractive index detector (RID); and HPLC-grade water as the eluent—gives precise and reproducible results regarding the detection of individual sugars in extracts of plants and feed materials. The method can be applied for the detection of sucrose; maltose; lactose; xylose; glucose; galactose; arabinose; fructose; ribose; and mannitol. Furthermore; depending on the plant material; the sugars verbascose; stachyose; and raffinose can be separated. The peaks were well resolved and the reproducibility of the analysis; with 94–108% of recovery (RC) and relative standard deviation (RSD) of up to 5%; was very good. The method was successfully applied to a variety of green forages and samples of sugar beet pulp silages. It is also possible to determine fructan with inulin as a standard; together with the other sugars; or alone by a different protocol and column.