Interconversion and chromatographic separation of carbohydrate stereoisomers on polystyrene-divinylbenzene resins

Mutarotation of sugars causes distorted and splitted peaks in liquid chromatography. The shape of the elution profile is affected by the different anomeric and isomeric forms in solution. The rate of interconversion between the different forms relative to the propagation velocity in the column determines the extent of the distortion. This interplay of interconversion reaction and chromatographic separation was examined both experimentally and theoretically. Elution profiles resulting from pulse injections of glucose and fructose solutions at different flow rates and temperatures were analyzed both qualitatively and quantitatively. Adsorption equilibrium and reaction kinetic parameters were estimated by a simple fitting procedure, based on peak elution times and area ratios obtained from the analysis of the experimental profiles. To enhance the accuracy of the model parameters further, estimated reaction kinetic parameters were provided as an initial guess for inverse fitting to elution profiles, using a numeric mass balance model. Simulations with the numeric model, based on the enhanced parameters, allowed a very precise description of the experimental profiles. Accuracy of the fitted parameters was further confirmed through comparison with literature values. Reaction rate constants for the adsorbed phase were calculated and interpreted based on apparent rate constant values determined in this work, and on literature data for aqueous solutions.