| Ginseng radix,which is a widely used herbal medicine in the world,plays a therapeutic role in enhancing immunity,anti-tumor and anti-aging,and so on.However,the pesticide residues in ginseng radix and ginseng extract are a critical conditioning factor of the ginseng's quality and curative effect.It is of great practical value to research the methods of removing pesticide residues from ginseng extract.Silane-modified attapulgites?SMAs?were prepared with a series of silane coupling agents containing KH-550,KH-602,KH-792,KH-1161,which were marked as KH-550-SMA,KH-602-SMA,KH-792-SMA,KH-1161-SMA.Five cationic-modified attapulgites?CMAs?were obtained by five cationic surface activators including dodecyl trimethyl ammonium bromide?DTAB?,tetradecyl trimethyl ammonium bromide?TTAB?,hexadecyl trimethyl ammonium bromide?CTAB?,octadecyl trimethyl ammonium bromide?STAB?and dodecyl trimethyl ammonium chloride?DTAC?,which were called as with DTAB-CMA,TTAB-CMA,CTAB-CMA,STAB-CMA and DTAC-CMA respectively.To evaluate the absorbing capacity of SMAs and CMAs,a spiked ginseng extract sample was constructed by adding five pesticides including propamocarb,isoprocard,quintozene,chlorpyrifos and tetramethirn.The removal effects of five pesticide residues in ginseng extract were analyzed by the absorption of organic-modified attapulgites.The results showed that KH-1161-SMA and STAB-CMA had the optimal removing efficient of the pesticide residues in ginseng extract among different organic-modified attapulgites.The best effect for organic-modified attapulgites to remove pesticide residues from ginseng extract were KH-1161-SMA modified with 80 g·kg-1 acidified attapulgite and STAB-CMA modified with 120g·kg-1 attapulgite.The adsorption models of five pesticides were consistent with the Langmuir isotherm equation and the Freundlich isotherm adsorption model,and the adsorption kinetics were consistent with quasi-secend-order kinetic equation.organic-modified attapulgites could strongly neutralize acidic or alkali ginseng extract,so the pH value did't affect much of adsorption between pesticides and organic-modified attapulgite clay.The test results of UPLC showed that the content was made for 4.36%loss in ginsenosides after adsorption of pesticide.The structure and specific surface area of organic-modified attapulgites were characterized by FT-IR,XRD,BET and SEM.The purpose was to investigate the adsorption performance and adsorption mechanism.The attapulgite is agglomerated in a block shape,which exhibited a parallel aggregates of fibrous structure.Compared with attapulgite,fibers were found to be interknitted resembling a woven texture in KH-1161 and the struture of individual fibers was looser.In addition,the pore of KH-1161-SMA was smaller and the specific surface area was larger.These changes would result in stronger adsorption capacity of KH-1161-SMA.The adsorption capacity of quintozene was increased to 182?g·g-1 from 155?g·g-1 of attapulgite.The structure of attapulgite remained intact modification after grafting with STAB and the adsorption capacity of quintozene was increased to 176?g·g-1from 122?g·g-1.The removal of pesticide residues in ginseng extract by organic-modified attapulgite overcomes the problems of long-term sample pretreatment,non-universal application clay,and safety hazards in the application for removal of pesticide residues in traditional Chinese medicine.Therefore,organic-modified attapulgite clay are new adsorption materials with potential applications. |
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