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Aqueous two-phase system (ATPS) is a new kind of extraction system which has beenwidely studied by scientists in scientific fields. In this aqueous two-phase extraction system,the mixture solutions of organic solvent or organic solvent with salts could separated into twophase, organic solvent or salt could enter into the different phase. While in the aqueoustwo-phase extraction system(ATPES), the target objects will distribute selectively in the twophase because of the existence of van der Waals’ forces, hydrophobic effect,hydrogen-bonding, electric charge among the molecules and so on.This paper established a new type of aqueous two-phase system, two small moleculealcohol/salt aqueous two-phase system, and the participation behavior of solubilityoxytetracycline hydrochloride (OTC) and insoluble sulfadiazine (SD) in this system wasinvestigated. The main research contents and conclusion are as follows:(1) Based on the principle of cloud point titration and unitary aqueous two-phase system,a new system using ethanol and n-propanol with ammonium sulfate binary aqueous two-phasesystem was set up. The relationship of substances concentration was talked about, and phasediagram was set up.(2) The distribution behavior of solubility oxytetracycline hydrochloride (OTC) in thetwo small molecule alcohol/salt system was discussed. The influence factors on partitionbehaviors of Oxytetracycline hydrochloride (OTC) were studied,including the systemcomposition,type and amount of salts, the pH value,the extraction temperature, standingtime after centrifuge and concentration of oxytetracycline hydrochloride (OTC).The results show that: when the system was1and1for the volume ratio of ethanol andn-propanol, NaH2PO4concentration of4.80mg/L, the pH value was4~5,temperature was25±0.5℃,and standing12hours, the partition coefficient of Oxytetracycline hydrochloride(OTC) was21.95, and extraction rate was86.09%.(3) The distribution behavior of insoluble sulfadiazine (SD) in the two small moleculealcohol/salt system was discussed. The influence factors on partition behaviors ofSulfadiazine (SD) were studied,including the type and amount of salts, the pH value,and standing time after centrifuge. The results show that: when the system was1and1for thevolume ratio of ethanol and n-propanol,(NH4)2SO4concentration of4.0mg/L, the pH valuewas4.0~5.0,temperature was25±0.5℃,and standing10hours, the partition coefficient ofsulfadiazine (SD) was33.49, and extraction rate was96.97%.
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