Miscible organic solvents

In the isolation of organic compounds from aqueous solutions, use is frequently made of the fact that the solubility of many organic substances in water is considerably decreased by the presence of dissolved inorganic salts (sodium chloride, calcium chloride, ammonium sulphate, etc.). This is the so-called salting-out effect. A further advantage is that the solubility of partially miscible organic solvents, such as ether, is considerably less in the salt solution, thus reducing the loss of solvent in extractions. 

In reversed-pViase chromatography (RPC), the mobile phase modulator is typically a water-miscible organic solvent, and the stationary phase is a hydrophobic adsorbent. In this case, the logarithm of solute retention factor is commonly found to be linearly related to the volume fraction of the organic solvent. 

If the column is contaminated with hydrophobic compounds, clean it with water-miscible organic solvents such as MeOH, CHjCN, or EtOH. Concentrations of 10-20% organic in water should be sufficient for cleaning. 

It has been found that the growth hormone can be obtained in crystalline form from human pituitary glands by procedures comprising (1) extraction of the fresh glands with acetone, (2) extraction of the acetone residue with aqueous salt solutions, (3) precipitation from aqueous salt solutions by the addition of suitable miscible organic solvents of alkaline and acid pH, and finally crystallization from aqueous salt solutions by the addition of suitable miscible organic solvents. 

As described above, the enzymatic polymerization of phenols was often carried out in a mixture of a water-miscible organic solvent and a buffer. By adding 2,6-di-0-methyl-(3-cyclodextrin (DM-(3-CD), the enzymatic polymerization of water-insoluble m-substituted phenols proceeded in buffer. The water-soluble complex of the monomer and DM-(3-CD was formed and was polymerized by HRP to give a soluble polymer. In the case of phenol, the polymerization took place in the presence of 2,6-di-O-methyl-a-cyclodextrin (DM-a-CD) in a buffer. Only a catalytic amount of DM-a-CD was necessary to induce the polymerization efficiently. Coniferyl alcohol was oxidatively polymerized in the presence of a-CD in an aqueous solution. ... 

The membrane is critically important in osomometry. Selection of a membrane involves reconciliation of high permeability toward the solvent with virtual impermeability to the smallest polymer molecules present in the sample. Membranes of cellulose are most widely used. Commercially Regenerated cellulose film is a common source. The undried gel cellophane film is often preferred, but the dry film may be swollen in water (or in aqueous solutions of caustic or zinc chloride ) to satisfactory porosity. Useful cellulose membranes may also be prepared by denitration of nitrocellulose films/ and special advantages have been claimed for bacterial cellulose films. The water in the swollen membrane in any case may be replaced by a succession of miscible organic solvents ending with the one in which osmotic measurements are to be made. Membranes of varying porosity may be... 

Tissue samples are homogenized in the presence of a water miscible organic solvent to promote efficient extraction. 

The isocratic reversed phase solvent system consists of water (polarity, p = 10.2), the most polar solvent in RPLC, as a primary solvent to which water-miscible organic solvents such as methanol (p = 5.1), acetonitrile (p = 5.8), or tetrahydrofuran (p = 4.0) are added. In order to optimize the speed of separation for an analyte pair, the proportions of water to nonpolar solvent are chosen such that the capacity factor of the last-eluting analyte of interest has a value of about 2.13... 

Mathieu, S., F. Bigey et al. (2007). Production of a recombinant carotenoid cleavage dioxygenase from grape and enzyme assay in water-miscible organic solvents. Biotechnol. Lett. 29(5) 837-841. 

Vazquez-Duhalt, R. Semple, K. M. Westlake, D. W. S., and Fedorak, P. M., Effect of Water-Miscible Organic-Solvents on the Catalytic Activity of Cytochrome-C. Enzyme and Microbial Technology, 1993. 15(11) pp. 936-943. 

Torres, E. Tinoco, R., and VazquezDuhalt, R., Solvent Hydrophobicity Predicts Biocatalytic Behaviour of Lignin Peroxidase and Cytochrome C in Aqueous Solution of Water-Miscible Organic Solvents. Journal of Biotechnology, 1996. 49(1-3) pp. 59-67. 

Dissolve the bis-NHS-PEG compound in a dry, water-miscible organic solvent to make a concentrated stock solution. To prepare a lOmM solution of the bis-NHS-PEG9 reagent, dissolve 7mg/ml of DMAC for the bis-NHS-PEG5 reagent dissolve 5.3mg/ml of DMAC. 

The NHS ester compounds are sensitive to hydrolysis in aqueous solution, and they likely will hydrolyze faster than more hydrophobic biotinylation compounds due to their hydrophilic-ity. If a stock solution is made at a higher concentration to facilitate the addition of a small amount to a reaction solution, the initial solution should be made in a water-miscible organic solvent that is dried with a molecular sieve. Suitable solvents include DMAC, DMSO, or DMF. If using DMF, use only highly pure solvent, as it may contain amines that can react with the NHS ester groups (Figure 18.13). 

T. Montensinos, S.P. Munguia, F. Valdez, and J.L. Marty, Disposable cholinesterase biosensor for the detection of pesticides in water-miscible organic solvents. Anal. Chim. Acta 431, 231-237 (2001). 

The investigation of enzymes in water-miscible organic solvents trivially called non-aqueous enzymology about 20 years ago became an independent part of modem biochemistry and enzymology [174-176], In concentrated organic solvents, with the water content less than 10-15%, the enzymes are rather stable and can even retain their activity [176, 177], Recent studies even demonstrated improvement of the enzyme activity in concentrated organic solvents [178],... 

For many years, prior to the development of current phase-transfer catalytic techniques, tetraalkylammonium borohydrides have been used in non-hydroxylic solvents [see, e.g. I, 2], Originally, the quaternary ammonium borohydrides were obtained by metathesis in water or an alcohol [3, 4], However, with greater knowledge of the phase-transfer phenomenon, an improved procedure has been developed in which the ammonium salt is transferred into, and subsequently isolated from, dichloromethane [5, 6], In principle, it should be possible to transfer the quaternary ammonium borohydride for use in any non-miscible organic solvent. It should be noted, however, that quaternary ammonium cations are susceptible to hydrogeno-lysis by sodium borohydride in dipolar aprotic solvents to yield tertiary amines [4]. 

The structural integrity of enzymes in aqueous solution is often compromised by the addition of small quantities of water-miscible organic solvents. However, there are numerous examples, particularly using extremophiles, where enzymes have been successfully employed in organic solvent-aqueous mixtures.A good example is the savinase-catalysed kinetic resolution of an activated racemic lactam precursor to abacavir in 1 1 THF/water (Scheme 1.39). The organic solvent is beneficial as it retards the rate of the unselective background hydrolysis. 

The use of water-miscible organic solvent-water mixtures is a particularly attractive method for use with cofactor-dependent enzymes due to its simphcity. The high water content can allow dissolution of both enzyme and cofactor, whilst the water-miscible solvent can provide a dual role in both substrate dissolution and as a cosubstrate for cofactor recycling (substrate-coupled cofactor recycling).The asymmetric reduction of a ketone intermediate of montelukast using an engineered ADH in the presence of 50 % v/v isopropanol offers a powerful demonstration of this methodology (Scheme 1.55). 

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