Co-solvents, effect

Figure 2.7 Gas clnomatogram obtained for 500 jl1 of diluted gasoline in -pentane inti O-duced by concunent eluent evaporation, using w-heptane as the co-solvent. Reprinted from Journal of High Resolution Chromatography, 11, K. Grob and E. Muller, Co-solvent effects for preventing broadening or loss of early eluted peaks when using concunent eluent evaporation in capillary GC. Part 2 w-heptane in w-pentane as an example , pp. 560-565, 1988, with permission from Wiley-VCH.

Kumbar, S.G., Kulkarni, A.R., Dave, A.M., and Aminabhavi, T.M. An assessment of solubility profiles of structurally similar hazardous pesticide in water + methanol mixture and co-solvent effect on partition coefficient, J. Haz. Mater., 89 (2-3) 233-239, 2002. 

Najdanovic-Visak, V. et al.. Pressure, isotope, and water co-solvent effects in liquid-liquid equilibria of (ionic liquid + alcohol) systems, /. Phys. Chem. B, 107, 12797, 2003. 

Salt effects and co-solvent effects in electrophilic substitution at saturated carbon... 

Co-solvent effects are generally more difficult to interpret than are kinetic salt effects, largely because the addition of a new solvent produces much more violent changes in the reaction medium than does addition of an inert salt. The mechanism of substitution may therefore be affected by addition of a co-solvent this is es-picially true of reactions proceeding by mechanism SE2, where the SE2(open) and SE2(cyclic) transition states may be regarded as the two extremes of a whole range of transition states. 

In this particular case, it is known that the substitution in methanol itself is accelerated by the addition of inert salts, and hence that mechanism SE2(open) probably obtains in solvent methanol. The most reasonable interpretation of the co-solvent effect is, therefore, that mechanism SE2(open) obtains in all four reaction media, and that the transition state is stabilised relative to the reactants in the more aqueous media. 

As regards the end-of-run isomerization rates, whereas the experimental results show a maximum at roughly 50 mol% co-solvent, the simulated results show a continuous decrease in isomerization rate with co-solvent addition. This might suggest a higher extent of coke extraction with the n-pentane co-solvent relative to that predicted for hexene. Such solvent effects have been reported previously [11]. The model does not account for solvent type and is hence unable to predict co-solvent effect on the solubility of coke precursors. 

As the pseudo-ternary phase map indicates, the sulfolane-containing system used in this work solubilizes the organophosphate TBP very effectively. From the 50Z point on the E-W axis, over 60% oil can be added while a clear fluid solution is maintained Even at 80% water it is possible to add nearly 20% oil before turbidity and subsequent phase separation occurs. It is not known whether a true microemulsion exists in this clear region. However this enhanced solubilization of TBP is not simply a co-solvent effect of the sulfolane and water. This was confirmed by determining the maximum solulbility (6.7%) of TBP in a 2 1 (w/w) mixture of sulfolane and water, respectively. 

Fig. 2 A plot of (CO or H2)consumed Vs. time for hydroformylation of 1-hexene using ethylene glycol as a co-solvent Effect of CO partial pressure...

Zhang, Y, Schmidt, J., Talmon, Y, and Zakin, J. L., Co-solvent effects on drag reduction, rheological properties and micelle microslructures of cationic surfactants, J. Colloid Interface ScL, 286, 696-709 (2005b). 

Gii lu-Ustundag and Temelli [63] reviewed the effect of a co-solvent on the phase behaviom of lipids in SC CO2. They found that physical interactions between the solutes and co-solvent, such as dipole - dipole, dipole - induced dipole or induced dipole - induced dipole (dispersion) interactions and specific interactions such as H-bonding and charge transfer complexes, are important contributors to the co-solvent effect. The use of a cosolvent may also lead to a change in selectivity. The magnitude of the effect of the co-solvent is thus a combination of the solvent, the co-solvent, the solute and the operating conditions. 

Co-solvent effect of dissolved polymers Polymers in solution can act as solubilizers and increase the solubility of drugs, thus reducing the degree of supersaturation and the risk of drug precipitation (Rodrfguez-Hornedo and Murphy 1999 Warren etal.2010). 

Future research is required for Solubilising agents that increase bio-availability use of co-solvents effect of surfactants on properties of solubilised systems and interaction with components of the body and mixed micelle formation between surface active drugs and surfactants. 

Najdanovic-Visak, V., Esperanca, J.M.S.S., Rechelo, L.P.N., Nunes da Ponte, M., Guedes, J.R., Seddon, K.R. Szydlowski, J. (2002).Phase behaviour of room temperature ionic liquid solutions an unusually large co-solvent effect in (water + ethanol), Phys. Chem. Vol. 4 (No.lO) 1701-1703. 

Szydlowski, J. (2002). Phase Behaviour of Room Temperature Ionic Liquid Solutions An Unusually Large Co-Solvent Effect in (Water Plus Ethanol). Physical Chemistry Chemical Physics, Vol. 4, No. 10, pp. 1701-1703, ISSN 1463-9076 Ng, M. H., Choo, Y. M., Ma, A. N., Cheng, H. C. Hashim, M. A. (2004). Separation of Vitamin E (Tocopherol, Tocotrienol, and Tocomonoenol) in Palm Oil. Eipids, Vol. 39, No. 10, pp. 1031-1035, ISSN 0024-4201... 

Noij, T.H.M. and van der Kooi, M.M.E. (1995) Automated analysis of polar pesticides in water by on-line solid phase extraction and gas chromatography using the co-solvent effect, /. 

The solubility data reviewed in Tables 20.4.13 to 20.4.17 reveal that the solubility of solutes was differently influenced by the presence of water in ethyl lactate solvent. For example, the solubility of thymol was not changed by water, that of vanilhc acid and caffeine was only slightly influenced, and a significant increase of the solubility of ferulic and caffeic acids were observed when the content of water in ethyl lactate was increased. Taking into account a low solubility of ferulic and caffeic acids in water, this solubility enhancement suggests a co-solvent effect which may have implications in potential extraction processes. 

In both,the co-solvent effect is expressed thermodynamically by the transfer free energy of the protein from water to the co-solvent containing medium, 4 2 = 2,m3 vvhere the subscript w refers to... 

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