SOIL SACCHARIDE EXTRACTION AND DETECTION

Extraction of soil saccharides involves the use of reagents effective in breaking hydrogen and covalent bonds between soil constituents and the saccharides. Of the many extractants proposed for saccharide determination, water is commonly used for extraction of water-soluble mono- and polysaccharides in soil. Analysis of these water extracts by colorimetric assays (anthrone-sulfuric acid and phenol-sulfuric acid methods) often show color development indicating that saccharides are present. However, high performance liquid chromatography (HPLC) and gas chromatography analyses have indicated that these colorimetric assays are prone to errors due to interferences from inorganic soil constituents such as Cl- NO3- and Fe+3. When water extracts (25-degrees or 80-degrees-C) are put through deionization resins to remove interferences little to no saccharides are present when assayed by the phenol-sulfuric acid analysis. The inability of water to extract saccharides from soil or microbial polymers was confirmed by HPLC analysis. The phenol-sulfuric acid assay was found to be acceptable for saccharide analysis of soil extracts only after being subjected to resin deionization for interference removal. The anthrone-sulfuric acid method is not considered acceptable for determining saccharides in soil.