Extraction, two-phase

In a simple liquid-liquid extraction the solute is partitioned between two immiscible phases. In most cases one of the phases is aqueous, and the other phase is an organic solvent such as diethyl ether or chloroform. Because the phases are immiscible, they form two layers, with the denser phase on the bottom. The solute is initially present in one phase, but after extraction it is present in both phases. The efficiency of a liquid-liquid extraction is determined by the equilibrium constant for the solute s partitioning between the two phases. Extraction efficiency is also influenced by any secondary reactions involving the solute. Examples of secondary reactions include acid-base and complexation equilibria. 

Many laboratory techniques have been described to purify proteins (25), but they are often too cosdy for industrial enzymes, especially column separations. However, aqueous two-phase extraction (26) and ion exchange are used. 

Consider a batch two-phase extraction system, with a single solute. 

Consider a batch two-phase extraction system, with a single solute transferring from the feed phase into an immiscible solvent phase. The background to the problem is discussed in Section 3.3.1.1... 

Piret, E. L., Ebel, R. A., Kiang, C. T. and Armstrong, W. P. Chem. Eng. Prog. 47 (1951) 405 and 628. Diffusion rates in extraction of porous solids-1. Single phase extractions 2. Two-phase extractions. 

Figure 8.8. Ligands for one-phase catalysis, two-phase extraction...

T0894 Xerox Corporation, Two-Phase Extraction System... 

T0885 Westinghouse Savannah River Company, In Situ Air Stripping T0894 Xerox Corporation, Two-Phase Extraction System T0896 Yellowstone Environmental Science, Inc. (YES), Biocat II T0900 Zenon Environmental, Inc., Cross-Flow Pervaporation System... 

The two-phase extraction process is a removal technology designed particularly for use in low conductivity formations such as silts and clays that are impacted by volatile organic compounds (VOCs). This technology removes VOCs from groundwater and/or soils. 

Two-phase extraction uses a vacuum source to remove contaminated groundwater and soil vapor from the subsurface. The vacuum is applied to an extraction tube within a water well to increase groundwater removal rates and to volatilize and extract VOCs. According to the vendor, vacuum lift of water is not a limiting factor in the application of the technology. Since a mixed vapor/liquid column is extracted from the weU, the two-phase extraction technology allows a single piece of equipment (a vacuum source) to remove contaminants in both the liquid and vapor phases. 

The two-phase extraction method was patented by Xerox Corporation. Xerox has granted licenses on the technology to several vendors, including Radian Corporation, Haley and Aldrich, and Hydro Group, Inc., who currently offer the technology. 

In 1996, the Environmental Process Improvement Center (EPIC) estimated the remediation costs for a two-phase extraction process would range from 70 to 160/lb of VOCs removed. EPIC is an alliance between the U.S. Department of Defense s (DOD s) McClellan Air Force Base, the U.S. Environmental Protection Agency (EPA), and the Cahfomia Environmental Protection Agency (Cal-EPA) (D21566H, pp. 1, 3). 

The Suzuki coupling reaction is a powerful tool for carbon-carbon bond formation in combinatorial library production.23 Many different reaction conditions and catalyst systems have been reported for the cross-coupling of aryl triflates and aromatic halides with boronic acids in solution. After some experimentation, we found that the Suzuki cleavage of the resin-bound perfluoroalkylsulfonates proceeded smoothly by using [l,l -bis (diphenylphosphino)ferrocene]dichloropalladium(II), triethylamine, and boronic acids in dimethylformamide at 80° within 8 h afforded the desired biaryl compounds in good yields.24 The desired products are easily isolated by a simple two-phase extraction process and purified by preparative TLC to give the biaryl compounds in high purity, as determined by HPLC, GC-MS, and LC-MS analysis. 

Typically, in a system such as PEG/dextran or PEG/phosphate, cell debris of a lysed and homogenized fermentation broth will partition to the bottom (dextran or salt) phase whereas the target protein partitions go to the top (PEG) phase. As the partition coefficient often is not much different from 1 (typically between 1 and 5) and PEG would disturb further processing, a second two-phase extraction with the PEG phase, typically with a much lower salt content to salt-in the protein, is necessary to recover the target protein. 

For modeling of aqueous two-phase extractions systems, see Abbott (1990,1992a-c, 1993). 

After the initial purification steps of salt precipitation of an aqueous two-phase extraction, an enzyme is often already pure enough for preparative use. If a high degree of purity or even homogeneity is required, such as for biochemical investigations of a novel enzyme, fine purification steps have to be added. The most common such step is chromatography. 

M. -R. Kula, Trends and future prospeds of aqueous two-phase extraction, Bioseparation 1990, 1, 181-189. 

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