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The effect of adsorption separation mainly depends on the resin used. The method of using the resin also has a great influence on the separation effect. Therefore, these two aspects need to be considered when carrying out a specific separation.
l Selection of adsorption resin
From the terminology, adsorption and separation are two concepts, but the purpose of adsorption is mostly for separation.
There are two types of adsorption resins: ▲ Broad-spectrum adsorption resins ▲ Selective adsorption resins
- The characteristics of broad-spectrum resins are: large attached amount and easy elution, but the purity of the obtained product is low;
- The characteristics of selective resins are: high selectivity for adsorption and adsorption of the target, high purity of the product, but sometimes low adsorption capacity.
If soy isoflavones are extracted, the adsorption and separation effects of different resins are shown in the figure below:
The extraction of Ginkgo biloba flavonoid glycosides also had similar results, as shown in the following table:
The selection principle of the adsorption resin should consider the special effect between a certain group in the target molecule and the functional group of the resin, so as to realize the separation from other substances. Such as:
★Metal Al-loaded resin (ADS-11) can complex with flavonoid molecules. Based on this mechanism, ADS-11 can increase the purity of 12% sea buckthorn flavonoids to 55%;
★The pore size of ADS-4 is only 1.3nm, which can absorb small molecules of impurities, but the steviol glycosides with a molecular weight above 500 cannot enter, so it can purify stevioside and increase the purity of stevioside from 90% to 95~98%;
★The -OH group of ADS-31 can form hydrogen bonds with compounds containing ester and amine groups. This mechanism can be used to separate natural products such as alkaloids and esters.
★ADS-7, D280, D301R have strong polar amine groups, which can not only adsorb acidic substances, but also have a strong affinity for natural pigments with conjugated double bonds. They are good for decolorizing natural products. effect.