Phase solubility analysis, interacting

A basic exposition of Gibbs phase rule is essential for understanding phase solubility analysis, and detailed presentations of theory are available [41,42]. In a system where none of the chemical species interact with each other, the number of independently variable factors (i.e., the number of degrees of freedom, F) in the system is given by... 

Anionic and neutral polymers are usually analyzed successfully on Syn-Chropak GPC columns because they have minimal interaction with the appropriate mobile-phase selection however, cationic polymers adsorb to these columns, often irreversibly. Mobile-phase selection for hydrophilic polymers is similar to that for proteins but the solubilities are of primary importance. Organic solvents can be added to the mobile phase to increase solubility. In polymer analysis, ionic strength and pH can change the shape of the solute from mostly linear to globular therefore, it is very important to use the same conditions during calibration and analysis of unknowns (8). Many mobile phases have been used, but 0.05-0.2 M sodium sulfate or sodium nitrate is common. 

Problems with adsorption onto the packing material are more common in aqueous GPC than in organic solvents. Adsorption onto the stationary phase can occur even for materials that are well soluble in water if there are specific interactions between the analyte and the surface. A common example of such an interaction is the analysis of pEG on a silica-based column. Because of residual silanols on the silica surface, hydrogen bonding can occur and pEG cannot be chromatographed reliably on silica-based columns. Eikewise, difficulties are often encountered with polystyrenesulfonate on methacrylate-based columns. 

Gennaro, M. C., Bertolo, P. L., and Marengo, E., Determination of aromatic amines at trace levels by ion interaction reagent reversed-phase high-performance liquid chromatography. Analysis of hair dyes and other water-soluble... 

Two of the worst outliers were N,N-dimethylformamide and N,N-dimethyl-acetamide. For both of these, solubility in water was greatly underestimated. This may illustrate a situation in which conformation does assume importance. In the gas phase structures used to compute the surface properties, the nitrogens are planar. There is reason to believe, however, that interaction with water molecules will cause the nitrogens to become pyramidal,48 since that produces more localized lone pairs that better attract water hydrogens. Thus, analysis involving planar nitrogens would not indicate the true strength of the interaction. 

In systems where the liquid phase interaction between the solute and solvent is close to ideal, then Eq. 2 can be used successfully on it s own to fit and extrapolate solubility data with respect to temperature. The technique is valuable in an industrial setting, where time pressures are always present. Solubility data points are often available without any additional effort, from initial work on the process chemistiy. The relative volume of solvent that is required to dissolve a solute at the highest process temperature in the ciystallization is often known, together with the low temperature solubility by analysis of the filtrates. If these data points fit reasonably well to the ideal solubility equation then it can be used to extrapolate the data and predict the available crystallization yield and productivity. This quickly identifies if the process will be acceptable for long term manufacture, and if further solvent selection is necessary. 

The analysis providing interaction second virial coefficients from chromatography rests upon three principal assumptions 1) vapor-liquid equilibrium exists in the column 2) the solute (component 1) is soluble in both the carrier gas (component 2) and the stationary liquid phase (component 3) 3) the carrier gas and stationary liquid are insoluble. Under assumption 1, we can write... 

To determine the composition of bimetallic alkoxides formed via complex formation in solution and in the solid phase and to estimate their stability, we have applied physicochemical analysis — the investigation of the solubility isotherms in the systems M(OR)m- M (OR)n - L (solvent alcohol, ether, hydrocarbon, etc.). This method, common for the studies ofthe interaction of inorganic salts in water solutions, turned out to be rather fruitful in the chemistry of alkoxides. It permitted the study of the interaction ofthe components... 

Quantitative PXRD and thermal analysis have been used to determine solid solubility of drugs in polymeric carrier [132-134], When phase separation occurs in solid dispersion, it results in formation of a drug-rich phase and a polymer-rich phase. The polymer-rich phase could retain, either by restricting molecular mobility or by interacting with drug, a certain portion of drug within its matrix. 

Wolfenden, R.V. (1978) Interaction of the peptide bond with solvent water a vapor phase analysis. Biochem. 17, 201-204. Yalkowsky, S.H., Valvani, S.C. (1980) Solubility and partitioning I Solubility of nonelectrolytes in water. J. Pharm. Sci. 69(8), 912-922. 

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