Partial solubility parameters

Fig. 4.22 Comparison of measured and calculated distribution ratios of americi-um(III)-terpyridine-decanoic acid complexes between 0.05 M HNOj and various organic solvent combinations. The calculated values are obtained with the Hansen partial solubility parameters. (From Ref. 45.)... 

Richardson, P. J., D. F. McCafferty, and A. D. V foolfson. 1992. Determination of three-component partial solubility parameters for temazepam and the effects of change in partial molal volume on the thermodynamics of drug solubility J. Pharm. 78 189-198. 

Wu, P. L, A. Beerbower, and A. Martin. 1982. Extended Hildebrand approach Calculating partial solubility parameters of solid solutaii.Pharm. Sci71 1285-1287. 

The modiLed solubility parameter in Equation 3.7 is different from the Hildebrand solubility parameters but is similarto the sum of the dispersion solubility pararfl tend the polarsolubility parameter, of the Hansen partial solubility parameters (Hansen, 1967). Values of the modiLed solubility parameters can be determined from the solubility of the solute in a nonpolar solvent. For example, pentane has been used as a solvent to determitsfeotlhieiethyl paraben (Ruelle et al., 1991). 

Some examples of partial solubility parameters (cal,/2cm 3/2) for compounds of chromatographic interest [209]. 

The behaviour of the perfluorinated phases as discussed above illustrates the fact that the solubility parameter model, despite its charms, may only be used as a crude approximation. The occurrence of specific deviations from the general rule may at least be made plausible by differentiating between different kinds of molecular interactions, and by introducing so-called partial solubility parameters or partial polarities [303,312] (see also section 2.3.1). However, such an extension greatly increases the complexity of the model, without increasing its predictive value correspondingly. 

Krause S (1987) Partial solubility parameter characterization of interpenetrating microphase membranes. In Lloyd DR (ed), Material science of synthetic membranes, ACS Symposium Series 269, Washington DC, p 351... 

For true compatability of solute and solvent, matching of all these partial solubility parameters (i.e., 8, Bp, 8 ) is necessary. The total solubility parameter can be easily calculated [1, p. 307] finm the material s enthalpy of vaporization, vapor pressure as a function of temperature, surface tension, thermal expansion coefficient, critical pressure, and second virial coefficient of its vapor, as well as by calculating its value for the chemical structure of the material. For the calculation of the Hildebrand solubility parameter fi om chemical structure, we use Small s [58] equation ... 

Hildebrand total solubility parameters for many solvents [591 are given in the appendix of this book. The partial solubility parameters, Sd,, Sff > can also be determined by chemical properties of the material... 

For nonionic surfactants, an optimization of the process was achieved by using a similar approach to the so-called Cohesive Energy Ratio (CER) concept developed by Beerbower and Hill for the stability of classical emulsions (H). Its basic assumption is that the partial solubility parameters of oil and emulsifier lipophilic tail and of water and hydrophilic head are perfectly matched. Thus, the Vinsor cohesive energy ratio Ro, which determines the nature and the stability of an emulsion, is directly related to the emulsifier HliB (hydrophile-lipophile balance) by... 

Partial Solubility Parameter Characterization of Interpenetrating Microphase Membranes... 

The simplest criterion for a theoretical calculation of the miscibility of the hydrophobic portions of small molecules with the hydrophobic microphase of a membrane polymer appears to be a partial solubility parameter that is, calculation of the solubility parameter of only the hydrophobic portions of the molecules. This can be done using a group contribution approach in which each group (for example, a CHg-group) in the molecule contributes a certain attractive force and a certain volume to the molecule. In this way, a solubility parameter may be estimated for either a portion of a molecule or for a whole molecule. 

While this review article was in press, a complete set of partial solubility parameters was published by Archer [167] based on solubility data. These parameters concern MC, the four types of HPMC (Table 6) and several ethylcelluloses with various ethoxyl contents. 

Table 15. Moisture content MC of some water-soluble derivatives after 30 day storage at 74% relative humidity and hydrogen-bonding partial solubility parameter 5,1...

The solubility method has the advantage that the values of the Hansen s partial solubility parameters, 5., 5. and 5., can be calculated from the molecular stmcture using the additive group... 

The choice of emulsifier is critical since it controls the stability of the emulsions prior to and after polymerization. Moreover, polymerization conditions typically represent destabilizing factors vigorous stirring, temperature rise and evolution of acrylamide content in the aqueous phase. In the case of inverse emulsions, the HLB values mostly used by the formulators range between 4 and 6. Some attempts were made to predict quantitatively the optimal HLB value corresponding to the most stable dispersions [18,19]. The treatment was based on the so-called cohesive energy ratio (CER) concept devekq)ed by Beer-bower and Hill for conventional emulsions [20]. Tins approach is based on a perfect chemical match between the partial solubility parameters of oil (ig)... 

I summarize briefly below the basic concepts of this approach, which is derived from that developed by Beerbower and Hill [31] for the stability of classical nonionic emulsions, which is referred to as the cohesive energy ratio (CER) concept. The treatment lies in a perfect chemical match between the partial solubility parameters of oil ( ) and surfactant lipophilic tail 6]) and of water and hydrophilic head. Under these conditions, one obtains for the optimum HLB (hydrophile-lipophile balance) of the surfactant the relation... 

Table 1 Solubility parameters and partial solubility parameters (expressed in caC ml for some compounds...

Using, for injection, an appropriate substance according to the chemical composition of the stationary phase, gas-liquid chromatography allows the identification of the various types of intermolecular interactions which occur between the stationary phase and the solute and the determination of their contribution to the total energy of interaction [69—72]. From the above-mentioned contributions, one can determine, as a rule, the partial solubility parameters of the polymer due to the various types of interacting forces (eqn (4.98)). 

The total solubility parameter of a resin or polymer is the point in three-dimensional space where the three partial solubility parameter vectors meet as the center point of the idealized spherical envelope. The distance in space between the two sets of parameters (solvent and polymer) can be represented by the radius of interaction term, R (Equation 1.2). 

In Equation 4.2 the i terms correspond to the parameters of the resin and the j terms to the parameters of the solvent. This equation measures the distance in three-dimensional space between the total solubility parameters of the solvent and resin. The total solubility parameter, 5, is a point in space where the three partial solubility parameter vectors meet. If the calculated radius of interaction, of the solvent and resin combination is less than the radius of the resin solubility sphere then the solvent will probably dissolve the resin and the solvent s solubility point will fall within the solubility sphere of the resin (Figure 4.1). A poor resin solvent would have a solubility point outside the resin envelope. Calculation of the radius of interaction for solvents and resins can be made easy through the use of the computer spreadsheet described in Chapter 19. 

Coating and paint formulations, adhesives, polymer-plasticizer compatibility and solvent effects on plastic surfaces are only a few of the areas that can benefit from the Hansen solubility parameter theory. Hansen [1] extended the solubility concepts discussed in Chapter 4 to include resin and polymeric materials. The total solubility parameter of a polymer is the point in three-dimensional space where the three partial solubility parameter vectors meet as the center point of the idealized spherical envelope. The distance in space between the two sets of parameters (solvent and polymer) can be represented by the term, radius of interaction or R. The radius of interaction term is used to express the degree of mutual solubility. All of these solubility comparisons can be made by using computer spreadsheets that are described in Chapters 4, 19, and this chapter. 

Hansen [1] pioneered the classification of polymeric materials in terms of the three partial solubility parameters. The solubility parameters of many polymers may be found in standard references like Barton s handbooks [2,3]. Estimates of the polymer solubility parameters as determined from the group contribution theory based on chemical structure are also described in Barton s books. The most exact determinations utilize the solubility behavior of the polymer in a series of solvents with varying degrees of polarity and hydrogen bond character (hexane to water). Hansen first used this type of solubility... 

Triangular plots are also used where the three solubility parameter values are expressed as fractional parameters. Fractional solubility parameters were suggested by Teas [5] where the fractional value of each solubility parameter is equal to that value divided by the sum of all three partial solubility parameter values. 

Table 10.8 lists the solvent-resin radius of interaction values ( / ) of five resins with each of five amides, acetonitrile, and two morpholine derivatives. These values are a measure of the solubility of the resin in the solvent. As described in Chapter 5 the total solubility parameter of a resin is the point in three-dimensional space where the three partial solubility parameter vectors meet as the center point of the idealized spherical solubility envelope. The distance in space between two sets of solvent-resin parameters can be represented by the term radius of interaction, The Lotus spreadsheet, SPWORKS.WKl, which lists some 166 resins and polymers and 289 solvents, was used to calculate the R values given in Table 10.8. Small R values (e.g., less than 10) would signify good solvency for the resin while higher values would suggest a poor solvent for the resin. If the actual radius of the resin solubility envelope is known then the / value should be less than the resin radius if the solvent is to dissolve the resin.

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