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PubMed1985

Prediction of xanthine solubilities using statistical techniques.

Mixture response-surface methodology can be used as a technique to predict solubility in mixed solvent systems. The present report shows that if the intent is to predict solubility in nonideal solutions, mixture response-surface methodology is a better technique than one which assumes a particular mechanism to hold true. This is demonstrated by comparing the predictive ability of the mixture response-surface model with that of an extended Hildebrand approach to nonideal solutions. The nonideal systems are those used by Martin and co-workers involving the solubility of theobromine, caffeine, and theophylline in dioxane-water mixtures.

Caffeine↗

PubMed1985

Prediction of solubility in nonideal multicomponent systems using the UNIFAC group contribution model.

There is a need to identify suitable blends of solvents to dissolve drugs. Empirical approaches, such as trial-and-error and response surface, require several solubility measurements. In this study the UNIFAC method was used to predict solubility in highly nonideal multicomponent systems in which only the solute enthalpy of fusion and melting point must by measured. UNIFAC combines a group contribution approach with the UNIQUAC model for activity coefficients. Parameters characterizing interactions among constituent groups of a molecule have been previously determined from binary vapor pressure data. These tabulated group parameters are used to predict activity coefficients for newly synthesized compounds. These coefficients, together with the ideal solubility, permit a prediction of solubility. The solubility of 4-hexylresorcinol in ethyl acetate, ethyl myristate, and hexane mixtures was both measured and calculated using UNIFAC. The predicted solubilities were within 10% of the experimental solubilities for all but 3 of 21 mixtures. Since the method accounted for positive and negative deviations from ideality in a hydrogen-bonding system of molecules having different sizes, it shows great potential for use in pharmacy.

Acetates↗