Cosolvent mixture

Usually, the solubility of the salt is determined from separate, more concentrated solutions. To conserve on sample, the titration of the salt may be performed with an excess of the counterion concentration [479]. Also, some amount of sample salt may be conserved by titrating in cosolvent mixtures, where salts are often less soluble. 

Much effort has been expended on models that can be used to predict the solubility behavior of solutes, with good success being attained using a semi-empirical, group contribution approach [75]. In this system, the contributions made by individual functional groups are summed to yield a composite for the molecule, which implies a summation of free energy contributions from constituents. This method has proven to be useful in the prediction of solubility in water and in water-cosolvent mixtures. In addition to the simplest methodology, a variety of more sophisticated approaches to the prediction of compound solubility have been advanced [68]. 

Yalkowsky has shown that the solubility of a compound in a cosolvent mixture (S ) can be estimated through a log-linear solubility relation ... 

More recent work with cosolvency in dilute systems seems to indicate that the magnitude of the solubility enhancement is linear up to some 10-20% cosolvent fraction [55,172,184,250-262]. At very low concentrations of cosolvent, the assumption of non-interaction between the cosolvent and water cannot hold. In dilute solutions the individual cosolvent molecules will be fully hydrated and, as a result, will disrupt the water network structure. If the total volume disrupted is regarded as the extended hydration shell, and if Sc is the average solubility within this shell, then the overall solubility Sm in the water-cosolvent mixture will be approximated by... 

Jouyban, A., Soltanpour, S., Soltani, S., Chan, H. K., Acree, W. E. (2007) Solubility prediction of drugs in water-cosolvent mixtures using Abraham solvation parameters. J Plmrm Sci 10, 263-277. 

Iodoxvbenzoic acid (IBX) is also a useful oxidizing reagent. Insoluble in most solvents (except DMSO) it can be used with other cosolvent mixtures. 

The reaction mixture contains a dilute solution of benzophenone solute, a few mole percent isopropanol and the remainder supercritical carbon dioxide solvent. This is analogous to a solute dissolved in a supercritical fluid/cosolvent mixture. These types of systems are important because in many applications researchers have found that the addition of a small amount of cosolvent (such as acetone or an alcohol) of volatility intermediate between that of the solute and the SCF can greatly enhance the solubility of the solute (Van Alsten, 1986). 

Jouyban et al. (2004) applied ANN to calculate the solubility of drugs in water-cosolvent mixtures, using 35 experimental datasets. The networks employed were feedforward back-propagation errors with one hidden layer. The topology of neural network was optimized in a 6-5-1 architecture. All data points in each set were used to train the ANN and the solubilities were back-calculated employing the trained networks. The difference between calculated solubilities and experimental... 

Jouyban, A., M. R. Majidi, H. Jalilzadeh, and K. Asadpour-Zeynali. 2004. Modeling drug solubility in water-cosolvent mixtures using an arti cial neural netwEdfmaco59 505-512. 

S/v is the solubility in water, and f is the fraction of organic solvent in the cosolvent mixture. If the cosolvent mixture contains more than two organic solvents (i.e., a ternary or higher cosolvent mixture), the total drug solubility can be approximated by a summation of solubilization potentials as... 

Differences in solubility between different crystal forms alter the driving force for dissolution, controlled by the difference between the solution concentration and the saturation concentration (Cs - C). Hamlin et al. (1965) have shown that dissolution rate correlates well with solubility for a large number of pharmaceutical compounds varying in solubility from 0.01 to 10 mg/mD t 37 Nicklasson and Brodin (1984) have shown that using cosolvent mixtures fordrugs with poor aqueous solubility produces a good correlation between dissolution rate and solubility. 

Hovorka SW, Hageman MJ, Schoneich C. Oxidative degradation of a sulfonamide-containing 5,6-dihydro-4-hydroxy-2-pyrone in aqueous/organic cosolvent mixtures. Pharm Res 2002 19 538-545. 

The third uses another measured property of the chemical which can be related to solubility. Most notable is HPLC retention time, which is a measure of the partitioning of the chemical between an aqueous phase (or more usually a water-cosolvent mixture) and a stationary organic phase. Other properties exploited include boiling point, parachor, and solubility parameters. 

A limited number of studies have considered the use of surfactant and cosolvent mixtures to enhance the recovery of NAPLs (Martel et al., 1993 Martel and Gelinas, 1996). Martel et al. (1993) and Martel and Gelinas (1996) employed ternary phase diagrams to select surfactant+cosolvent formulatons for treatment of NAPL-contaminated aquifers. The surfactant+cosolvent formulations used in their work, which included lauryl alcohol ethersulfate/n-amyl alcohol, secondary alkane sulfonate/n-butanol, and alkyl benzene sulfonate/n-butanol, were shown to be effective solubilizers of residual trichloroethene (TCE) and PCE in soil columns (Martel et al., 1993). However, very little information is available regarding the effect of cosolvents on the solubilization capacity and phase behavior of ethoxylated nonionic surfactants. 

To evaluate the effects of cosolvent on surfactant delivery and PCE recovery, Box B was flushed with 4% Tween 80 + 5% EtOH at a Darcy velocity of 4.8 cm/hr. The surfactant/cosolvent mixture, which had a density of 0.994 g/cm3, was also representative of a neutral buoyancy flood solution (Shook et al, 1998). It is important to recognize that "neutral buoyancy" refers to density of flushing fluid after solubilization of the DNAPL. Thus, the initial density of the surfactant formulation must be less than that of the resident aqueous phase. Figure 5b shows the location and shape of the 4% Tween 80 + 5% EtOH front after flushing Box B with 0.5 pore volumes of solution. The lower density of the 4% Tween 80 + 5% EtOH solution (0.994 g/cm3) relative to the density of resident pore water (0.998 g/cm3) caused the injected solution to flow preferentially along the top of Box B (Figure 5b). This effect can become severe at low flow rates (Taylor, 1999). The... 

Cosolvent technology is similar to the surfactant enhancement technology. Instead of a surfactant, the injection well receives a solvent mixture (e.g., water plus a miscible organic solvent such as alcohol). The cosolvent mixture is injected up-gradient of the... 

In the talk, we present phase behavior data for copolymer-solvent-cosolvent mixtures at temperatures to 300 °C and pressures to 3,000 bar. We also present data on the impact of cosolvents on the phase behavior. 

Sc(OTf)3 and lanthanide triflates, particularly Yb(TOTf)3 have been shown to catalyze a variety of reactions in aqueous/organic cosolvent mixtures [145, 146]. 

Fig. 4.65 Pd-neocuproine as catalyst for alcohol oxidation in water/cosolvent mixtures.

A. K. Chatjigakis, I. Clarot, P. J. P. Cardot, R. Nowakowski, and A. Coleman, Reversed phase chromatographic study of the inclusion selectivity of terpene derivatives with P-cyclodextrines in water/cosolvent mixtures, J. Liq. Chrom Rel. Technol. 22 (1999), 1267. 

Materials.- All materials were commercial with the exception of the complex [C o(NH3)4(p2CX)2)](C104)2 which was prepared and recrystallized according to the method described in ref. 2. The water-cosolvent mixtures were made up by weight. 

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