Monday, April 30, 2007

Use of modern anion chromatography for the analysis of biomass hydrolyzates

David K. Johnson, Chemical and Biosciences Center, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401

High pressure liquid chromatography (HPLC) is the standard method for analysis of biomass hydrolyzates using columns containing cation exchange resins primarily in either of the lead or hydrogen ion forms.  With these columns it is possible to separate the major carbohydrate components of biomass hydrolyzates, however, peaks are not separated with baseline resolution and interference from “ghost' peaks can be a serious problem for good quantitative analyses.  In addition, di- and oligo- saccharides, and carboxylic acids are difficult to quantify and may even interfere with the quantification of monosaccharides.  Anion chromatography has some advantages over cation chromatography permitting near baseline separation of all the major monosaccharides and enough resolution to also separate less common monosaccharides (rhamnose, fucose, fructose, ribose, lyxose) that can be present in biomass hydrolyzates in minor amounts.  By adjusting the sodium hydroxide concentration of the eluent it is also possible to focus the separation on disaccharides such as cellobiose, maltose, isomaltose, and stachyose, with minimal interference from other components in biomass hydrolyzates.  A further modification of the eluent, adding acetate as a pusher ion, allows baseline separation of the uronic acid containing components (glucuronic acid, 4-O-methyl glucuronic acid, 4-O-methyl glucuronoxylose, and galacturonic acid) that can be found in biomass hydrolyzates.  The advantages and disadvantages of the anion and cation chromatography systems will be described.