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Aqueous biphasic systems (ABS) or aqueous two-phase systems (ATPS) are clean alternatives for traditional organic-water solvent extraction systems.. ABS are formed when either two polymers, one polymer and one kosmotropic salt, or two salts (one chaotropic salt and the other a kosmotropic salt) are mixed at appropriate concentrations or at a particular temperature.
Phase 1 is typically an organic solvent and 2 an aqueous phase. Laboratory-scale liquid-liquid extraction. Photograph of a separatory funnel in a laboratory scale extraction of 2 immiscible liquids: liquids are a diethyl ether upper phase, and a lower aqueous phase. Schematic representation of a Soxhlet extractor:
Under neutral conditions (pH 7-8), both DNA and RNA partition into the aqueous phase. In a last step, the nucleic acids are recovered from the aqueous phase by precipitation with 2-propanol. The 2-propanol is then washed with ethanol and the pellet briefly air-dried and dissolved in TE buffer or RNAse free water.
The distribution coefficient, log D, is the ratio of the sum of the concentrations of all forms of the compound (ionized plus un-ionized) in each of the two phases, one essentially always aqueous; as such, it depends on the pH of the aqueous phase, and log D = log P for non-ionizable compounds at any pH.
With a typical liquid mass diffusivity in the order of 10 −9 m 2 /s, [2] the characteristic time for diffusion through a 20 micron thick liquid layer is 0.4 s. Therefore, the thinness of both phases (organic and aqueous) causes a relatively "immediate" mass transfer of guest species from one phase to the other, which means that this process has a low mass transfer resistance.
The McCabe–Thiele method is a technique that is commonly employed in the field of chemical engineering to model the separation of two substances by a distillation column. [ 1 ] [ 2 ] [ 3 ] It uses the fact that the composition at each theoretical tray is completely determined by the mole fraction of one of the two components.
Di(2-ethylhexyl)phosphoric acid (DEHPA or HDEHP) is an organophosphorus compound with the formula (C 8 H 17 O) 2 PO 2 H. The colorless liquid is a diester of phosphoric acid and 2-ethylhexanol . It is used in the solvent extraction of uranium , vanadium and the rare-earth metals .
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