Selective ketopentose analysis in concentrate carbohydrate syrups by HPLC

A new high performance liquid chromatographic (HPLC) method is described for the selective determination of small quantities of ketoses obtained by the action of immobilized isomerases on wheat bran hydrolysates, in the concentrated syrups of the corresponding glucose, arabinose, and xylose. This method uses MilliQ water instead of dilute sulfuric acid as a mobile phase on an Aminex HPX-87H column. Excellent discrimination between xylulose and ribulose was achieved. Selective detection of ketoses was made possible by the much higher UV absorbance at 210 nm. The sensitivity limit is 0.5 g/L for D-xylulose and L-ribulose. The response is linear up to a 20 g/L ketose concentration regardless of the presence of less than 50 g/L of D-xylose or L-arabinose.