[Study of the adsorption properties in chromatographic separation of the citric acid]

A new method studying the change of thermodynamic properties at different temperatures to screen suitable stationary phases for chromatographic separation of the citric acid (CA) on an analytical column has been developed. The applied method is mainly based on using CA with a series of solute concentrations (0 g/L-250 g/L) as mobile phase to seriously overpass the unloaded stationary phase to find the breakthrough curves of CA. The adsorption isotherms were calculated from the retention times of breakthrough curve. The bed porosity of column was calculated from the elution time of a peak of the blue dextran as non-adsorbed tracer. The stationary phase, which has been selected through this method, for the separation of CA from fermentation broth, showed a very high adsorption capacity for CA, even under very low concentrations, so it can even be used in the separation and purification process of minute amounts of CA. The separation effect of this stationary phase for citric acid can be greatly enhanced through the technique of change of temperature. This new separation process can shorten the old process path, improve the yield of finished products more than 10%, and reduce the cost more than 10%. At the same time, the pollution of the production of citric acid can be reduced. It turned out that this method will play an important role in the synthesis of stationary phase for the separation of citric acid and the study of its structure.