Extraction potential

A. Ben-Naim, Statistical potentials extracted from protein structures Are these meaningful potentials J. Chem Phys. 107 (1997), 3698-3706. 

P.D. Thomas and K.A. Dill, Statistical potentials extracted from protein structures How accurate are they J. Mol. Biol. 257 (1996), 457-469. 

The most common method for screening potential extractive solvents is to use gas—hquid chromatography (qv) to determine the infinite-dilution selectivity of the components to be separated in the presence of the various solvent candidates (71,72). The selectivity or separation factor is the relative volatihty of the components to be separated (see eq. 3) in the presence of a solvent divided by the relative volatihty of the same components at the same composition without the solvent present. A potential solvent can be examined in as htfle as 1—2 hours using this method. The tested solvents are then ranked in order of infinite-dilution selectivities, the larger values signify the better solvents. Eavorable solvents selected by this method may in fact form azeotropes that render the desired separation infeasible. 

The silver(I) complexes with the tetrakis(methylthio)tetrathiafulvalene ligand have been reported, the nitrate salt presents a 3D structure with an unprecedented 4.16-net porous inorganic layer of silver nitrate,1160 the triflate salt presents a two interwoven polymeric chain structure.1161 The latter behaves as a semiconductor when doped with iodine. With a similar ligand, 2,5-bis-(5,5,-bis(methylthio)-l,3,-dithiol-2 -ylidene)-l,3,4,6-tetrathiapentalene, a 3D supramolecular network is constructed via coordination bonds and S"-S contacts. The iodine-doped compound is highly conductive.1162 (Methylthio)methyl-substituted calix[4]arenes have been used as silver-selective chemically modified field effect transistors and as potential extractants for Ag1.1163,1164... 

While not mandatory from regulatory guidehnes, much research has been carried out to investigate the extractability of plastic additives in contact with a variety of pharmaceutical formulations, mainly those for parenteral use. The research concentrates on the extractability of plasticizer phthalates, mainly di-2-ethylhexylphthalate (DEHP) from polyvinyl chloride (PVC) into the blood, blood components, and infusion solutions. The purpose for these studies lies in its, up to now, controversial hazardous effects on humans. The amount of additive necessary to turn rigid PVC into a flexible material (40% m/m) and the absence of chemical bonds between the polymer and the plasticizer make it a potentially extractable species. 

The protocols for staining with amido black, Coomassie blue, Ponceau S, and AuroDye follow the suppliers recommendations. It should be noted that when staining PVDF membranes with Coomassie blue before N-terminal sequencing, omitting acetic acid from both the stain and destain solution is recommended to minimize potential extraction of protein from the membrane (Speicher, 1989). 

A screening of the virtual combinatorial library was performed in several steps. As potential extractants must be insoluble in the water phase, the ISIDA-Log S module incorporating QSPR models for aqueous solubilities (log S)95 has been used for filtering the library. Thus, the compounds for which log S < -3 were considered insoluble in water other compounds were excluded. A subset containing 9,306 potentially insoluble molecules has been screened using the structure-log D models. The main goal of screening was the selection of potentially efficient extractants. However, in... 

Fig. 7.21 (continued) reverse scans. EE SS = —2.6V (vs. Ag), sw = 25mV, A s = 10mV. The values of the kinetic parameters and formal potential extracted in each case are given in Table 7.2. Test solution 2 mM 2-methyl-2-nitropropane, 0.1 M tetra-n-butylammonium perchlorate in acetonitrile. Reproduced from [30] with permission... 

It is assumed that treated water cannot be reinjected. The aqueous concentration at thirteen observation wells must be less than or equal to the water quality goal (0.5 mg/L) by the end of a 5-year remediation period. The locations of these potential extraction wells and observation wells are indicated in Figure 1. Thus, to complete the formulation of this problem, the following three constraints must be added to the management model described in Equations 4 to 11 ... 

Figure 1. Initial toluene plume (mg/L) and observation and potential extraction wells for Example 1.

A. Ben-Naim,/. Chem. Phys., 107, 3698 (1997). Statistical Potentials Extracted from Protein... 

The operating pressure is obtained from the vapor pressure and the partial pressure of the gaseous educts and products. In this process, the temperatures applied are between 150 and 500 °C. In recent times, supercritical fluids have attracted a great deal of attention as potential extraction agents and reaction media in chemical reactions. This has resulted from an unusual combination of thermodynamic properties and transport properties. As a rule supercritical reactions like hydrolysis or oxidation are carried out in water. Above the critical point of water, its properties are very different to those of normal liquid water or atmospheric steam. 

Some potential extractable chemicals from packaging materials are water soluble, while others are soluble only in nonpolar environments. The USP includes physicochemical tests for plastics based on water extracts, while water, alcohol, and hexane extracts are required for polyethylene containers under controlled temperature and time parameters (70°C for 24h for water and alcohol and 50°C for 24h for hexane). 

Several issues require investigations. Membrane filters shed particles or fibers released during filtration. This is an area where potential extractables may occur. The potential toxicity of the filters and the product s compatibility with the membrane must be determined. Of all the filters tested (unpublished data), polyvinylidene difluoride, polycarbonate, and polysulfone were found to be most compatible with several proteins, with minimal amounts of protein binding and deactivation. 

Vidal S, Neiva Correia Ml, Marques MM (2004) Studies on the use of ionic liquids as potential extractants of phenoUc compounds and metal ions. Sep Sci Technol 39 2155-2169... 

Interest in predicative testing extends not only to long periods of service but to relatively short time periods as well when biodegradability is concerned or in biocompatible systems in medical use whether it be in adhesion of bone or prosthesis or packaging is concerned, and in food additives when for example a species may be of consequence when present in the polymer and potentially extracted or present as a delicate flavor or color and absorbed by the maeromolecular system. 

Thomas, P. D. Dill, K. A. (1996). Statistical potentials extracted from protein structures how accurate are they ... 

Quantitative and (hopefully, at least) qualitative considerations are helpful in characterizing a liquid-liquid system for a potential extraction application. Batch shakeout tests are frequently the easiest way to determine basic feasibility by simply measuring the primary and secondary break times and by analyses to measure the compositions of the equilibrated phases. Such tests are readily conducted by mixing small volumes of each phase in a vial, which is then vigorously agitated and placed on a lab bench to settle. The resulting behavior of the liquid-liquid mixture depends on physical properties and system characteristics. The greater the density difference and interfacial tension between the two liquid phases, for example, the more rapidly the phases tend to separate. More viscous systems separate more slowly. 

Cyclic voltammetry is often used to obtain information about standard potentials for correlative studies of molecular properties (e.g., ionization potentials, electron affinities, molecular orbital calculations, etc.). How is a standard potential extracted from data of this sort Are assumptions involved What kind of error would appear if the electrode process were EC What if it involved slow electron transfer to a chemically stable product ... 

Before proceeding to develop a method for SFE of a natural product, the feasibility has to be ascertained. To determine the feasibility of SFE as a potential extraction technique, the solubility of the target compound in supercritical carbon dioxide or other supercritical fluid of choice (e.g., butane) has to be determined. If the compound is poorly soluble in supercritical fluid(s), SFE is probably not the preferred extraction method. Solubility experiments to determine the effect of temperature and pressure (which in turn control the density) on the solubility of the target compound in the supercritical fluid have to be performed. 

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