|Title:||The study of macroporous adsorption resin (MAR) on preparative separation and purification of saikosaponins from the crude herbal extract|
|Subject:||Hong Kong Polytechnic University -- Dissertations.|
Gums and resins.
Herbs -- Analysis.
|Department:||Department of Applied Biology and Chemical Technology|
|Pages:||xii, 124 leaves : ill. ; 31 cm.|
|Abstract:||Study was carried out to investigate the adsorption characteristics of saikosaponins a, c and d on the macroporous adsorption resins and the efficiency of the adsorption column for the separation and purification of saikosaponins from the crude herbal extract. Both static and dynamic experiments were conducted. In static studies, the performances of eight macroporous resins namely HPD100, HPD300, HPD400, HPD450, HPD500, HPD600, HPD700 and HPD800 for the adsorption of saikosaponins were evaluated. HPD100 was found to have the highest adsorption capacity. It indicated that the hydrophobic property of the resin played a significant role in the adsorption. The effects of temperature, initial saikosaponins concentration and pH on the adsorption on HPD100 were also investigated. The results showed that higher temperature and initial saikosaponins concentration could enhance the adsorption while the effect of pH was not significant. Furthermore, HPD100, HPD450 and HPD600 were selected for the studies of isotherms, kinetics and thermodynamic of adsorption. The adsorption data from the HPD100 resin fit well to the Langmuir model indicating the adsorption was monolayer, while those from the HPD450 and HPD600 resins fit to either the Langmuir model or the Freundlich model indicating the adsorption was either monolayer or multilayer. The positive value of the adsorption enthalpy and the negative value of the Gibbs free energy showed that the adsorption process was endothermic and spontaneous in nature, respectively. The adsorption on HPD100, HPD450 and HPD600 resins followed either the pseudo first order kinetic or the pseudo second order kinetic. The rate of adsorption process was found to be controlled by the film diffusion. In dynamic studies, the adsorption and desorption experiments were carried out on a column packed with HPD100 resin. The operating parameters including feed flow rate, feed concentration and bed depth were varied to investigate their effects on the adsorption performance of the column. The results show the breakthrough occurred earlier when the feed flow rate and feed concentration increased. In contrast, the breakthrough took place later when the bed depth increased. An efficient column operation of the adsorption step was obtained. In the elution step, step-gradient elution program with 120 ml 0%, 160 ml 25%, 160 ml 45%, 160 ml 65% and 120 ml 85% aqueous ethanol in succession was found to be the most proper program to achieve an efficient separation. The purity, concentration ratio and recovery yield of saikosaponins were ~20%, ~17 and ~70% respectively. In order to determine the reusability of the column, the adsorption/desorption (A/D) cycle was repeated a number of times. The results showed that after five successive A/D cycles, the column was able to retain over 50% adsorption capacity.|
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