Organic solvents, solubility

TSK-GEL SW columns allow use of elution buffers comprised completely of water-soluble organic solvents, whereas the TSK-GEL PW packings limit organic cosolvent use to a maximum of 50%. 

Soluble organic solvents have often been used as cosolvents to solubilize miscible organic substrates. Since organic compounds including solvents are possibly incorporated inside of the enzyme, they may affect the stereoselectivity of enzymatic reactions. For example, dimethyl sulfoxide (DMSO) (10%) enhance not only chemical yield but also enantioselectivity of yeast reduction. Thus, the poor yield of 23% with 80% ee was increased to 65% yield with >99% ee (Figure 8.20) [17]. 

Problem 14.60 Show how ethylene oxide is used to manufacture the following water soluble organic solvents ... 

By using water-soluble organic solvents, usually referred to as precipitants, the reaction can be directed to produce only one cyclodextrin. In the presence of toluene, the enzyme from B. macerans produces only (3-cyclodextrin and linear starch chains. Beta-cyclodextrin can be separated from the soluble starch chains and recovered as a precipitated toluene complex. In the presence of decanol, a-cyclodextrin is the only cyclodextrin produced using the enzyme from B. macerans.21,22 Precipitants such as large cyclic compounds similar to musk oil23 or a-naphthol and methyl ethyl ketone (butanone)24 can be used to produce 8-cyclodextrin. 

Since lipases act on lipids at lipid-water interfaces, preparation of substrates in a suitable physical form for maximal lipase activity is very important. Preparation methods include emulsification with an emulsifying agent incorporation into a gel dissolution in a water-soluble organic solvent, such as 2-methoxyethanol or tetrahydrofuran, followed by addition to an aqueous reaction mixture sonication, with or without emulsifier and formation of a thin film or monolayer. 

The reaction of isatin with thiophene in an acidic medium, containing ferrous ion, gives rise to an intense violet color, due to the formation of indophenine dyes. Due to this phenomenon, it was proposed that isatin could be used as a revealing agent for the presence of thiophene in water-soluble organic solvents where it is used as a denaturating agent637. 

A number of authors investigated the process of foam breakdown by antifoams introduced in the foaming system or the foam such as O/W emulsion and solutions in water-soluble organic solvents. Under such defoaming conditions the mechanism of antifoaming action becomes more complex and a destabilisation of the films is possible to occur by an entirely different (heterogeneous) mechanism (see below). 

The solubility of proteins and nucleic acids in aqueous solution depends on the solvation of the macromolecule by water this can be influenced by pH, ionic strength and temperature, and also by the addition of salts, or water-soluble organic solvents. We discuss below the various precipitation methods that have been used with proteins and nucleic adds, particularly with regard to concentration and fractionation procedures. 

The mobile phase in RPC contains water and one or more water-soluble organic solvents. The most useful are, in order of decreasing polarities, acetonitrile, methanol, dioxane, tetrahydrofuran and propanol. By the choice of the type of the organic solvent, selective polar interactions, dipole-dipole, proton-donor or proton-acceptor, with analytes can be either enhanced or suppressed and the selectivity of the separation adjusted. For simplicity, binary mobile pha.ses are used more often than those containing more than one organic solvent in water, as they often make possible an adequate separation of various samples. However, ternary or less often quaternary mobile phases offer advantage of fine-tuning the optimum selectivity of more difficult separations. This is discussed in more detail in Section 1.4.6. 

The solution is neutralized with dilute hydrochloric acid and transferred to the container used for collecting water-soluble organic solvents. 

The water-soluble organic solvents in commercially available solubilized oral formulations are polyethylene glycol 400 (PEG 400), ethanol, propylene glycol, glycerin, and Transcutol HP. The solvent Transcutol is purified diethylene glycol monoethyl ether and is a powerful solubilizer that is used in various European products. 

The range of complexity of solubilized oral formulations filled into a capsule varies from a simple one-excipient formulation such as PEG 400 or a long-chain triglyceride, to complex microemulsion preconcentrates which contain oil, cosolvent, and surfactant excipients. The preferred water-soluble organic solvents... 

Due to their good fat solubility, organic solvents also affect the natural fat layers of the skin, so in the case of permanent contact skin damages are possible. As preventive measures, the wearing of mbber gloves and the use of skin-protection cream are strongly recommended. 

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