Characterization of molecular weight distribution of oligomers from autocatalyzed batch hydrolysis of xylan

Oat spelt xylan was treated with water in a batch reactor at temperaturesof 180 and 200 degrees C. Ion-moderated partition (IMP) chromatography was thenapplied to separate oligomers in solution according to their molecular size. Calibration of the IMP measurements based on peak height was found toquantify dissolved monomer and oligomer yields well. Oligomer concentrationsin the liquid hydrolysate were also determined from the difference inxylose monomer concentrations measured by high-performance liquid chromatographybefore and after posthydrolysis of dissolved xylooligosaccharidesto xylose. Delayed formation and then rapid disappearance of oligomersfrom DP10 to DP2 was observed by IMP, and total oligomer yields measuredby IMP and posthydrolysis were very similar at these times. However, whileIMP detected virtually no oligomers initially, posthydrolysis measurementsgave significant amounts of soluble oligomers at these times, indicating thatoligomers with chain lengths >10 were in solution but not detectable by theIMP system used.