Quantification of Polysaccharides in Vegetable Raw Materials and Lignin Preparations

Abstract

The phenol-sulfuric acid method has been studied for its capability to analyze vegetable raw materials. This method has made it possible to determine rather simply and with high accuracy polysaccharides in both vegetable raw materials (agricultural vegetables, softwood, and hardwood), and in various lignin preparations (the laboratory-scale and technical). The method is based on the color reaction of monosaccharides with phenol in the presence of concentrated sulfuric acid. The developed modified phenol-sulfuric acid method is universal because allows for the detection of polysaccharides in the samples with both high and low polysaccharide content, i.e., in vegetable raw materials and lignin preparations, respectively. The method is highly sensitive; it is possible to analyze monosaccharides in the mixture at the concentration of 1 × 10^–4 mol L^–1 on average. The hydrolysate volume of 0.25 mL that is ten-times diluted is enough for analysis. The duration of the hydrolysate analysis including the mix preparation, recording of the spectrum, and calculation by the formula does not exceed 30 min. The method can be used for the analysis of the chemical composition of renewable vegetable raw materials when developing technologies for obtaining alternative energy sources.