Determination of partial and total cohesion parameters of caffeine, theophylline, and methyl p-hydroxybenzoate by gas-solid chromatography.

For the first time, the total and partial solubility parameters, delta t, delta d, and delta s, of caffeine, theophylline, and methyl p-hydroxybenzoate were obtained by gas-solid chromatography (from the adsorption internal energy), by using the Keller, Karger, and Snyder equation. In comparison with the solubilization techniques, this method has the advantage of giving single solubility parameter values. The experimental work has been reduced to a minimum by the optimization of the matrix of experiments, according to the D-criterion, without any diminution in the quality of the results.