Separation Conditions Of Catechins With Adsorption Chromatography And Its Application To Expanded Bed

Three adsorbents of PA, HI03 and XAD-4 were used to isolate catechins from green tea with column chromatography system and the expanded bed adsorption chromatography system. Through the systematic investigations of adsorptive performance, thermodynamic and kinetic characteristics of various adsorbents, and the elution performance of various eluants on resolution, we established the optimum conditions which could be applied to the separation of catechins effectively with expanded bed technology.The result of adsorption performance experiment showed that, the adsorption performance of PA, HI03 and XAD-4 were better, their equilibrium adsorption capacity were 405.06mg/ml, 394.97mg/ml and 208,77mg/ml respectively. The study of thermodynamic characterization showed that the adsorption isotherms of these three adsorbents could all be described by the Langmiur equation. And they all belong to the preferential isotherm and are highly related to the Langmiur equation. By studying the kinetic characterization and drawing the adsorption kinetic isotherms, we know that, PA and HI03 are middling speed adsorbents, while XAD-4 is low speed adsorbent. The constants of equilibrium rate of PA, H103 and XAD-4 are KPA=1.461h-1, KH103=1.198h-1, KXAD-4=0.498h-1 in order. They become lower in succession. The analysis of penetration curve showed that, the matter transfer zone of XAD-4 is longest, while the matter transfer zones of PA and H103 are shorter, which put good use of PA and H103.The study of the elution performance of various eluants showed that, the appropriate eluants for PA, H103 and XAD-4 to isolate catechins were 85% ethanol, mixture of 6.4% methanol-30.8% Acetonitrile-5.3% tetrahydrofuram-57.5% water, mixture of ethanol-ethyl acetate-water ( 1:3:1, v:v:v) respectively. By making contrastive analysis, we know that the best separation effect can be acquired by using PA as adsorbent and 85% ethanol as eluant. After taking the condition optimized experiment, we eventually chose the best method for column chromatography as below: use PA as adsorbent, use 45% and 85% ethanol as eluant, eluate in two steps with the velocity of 0.8ml/min. The cost is low by using this method, it is appropriate for the industrial production. And the toxicity of matters during the process is very small, so this method can be wildly used in medical andfood areas.After pilot study, it is found that applying the expanded bed technology to the separation process of tea cathechins, using expanded bed-column chromatography method to separate ester catechins, the extaction of tea polyphenols can be omitted. So the workload is reduced greatly and the work efficiency is increased. The separation effect for ester catechins is also better by using this method.