Determination of Solubility Parameters for Medicinals and Excipients

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Abstract
The solubility parameters of cefalexin, .alpha.-lactose monohydrate, controlled pore glasses with various pore diameters (75 to 1000 .ANG.) and silanized controlled pore glasses were determined by the gas-solid chromatographic method. As partial solubility parameters, dispersion term .delta.d and other specific interaction term .delta.s were used. The partial solubility parameters of .delta.d and .delta.s of .alpha.-lactose monohydrate were calculated to be 8.9 and 15.4 cal1/2/cm3/2, respectively and these values were in close agreement with those reported by Kesselring et al.2) On the controlled pore glasses, it was observed that the solubility parameters decreased from 106 to 76.6 cal1/2/cm3/2 with an increase in diameter of controlled pore glass, and that this decrease resulted from the variations of .delta.s values. To investigate the effects of surface hydrophilicity on solubility parameters of controlled pore glasses, silanol groups were inactivated by silanization. The solubility parameters could explain porous properties depending on the pore diameters of controlled pore glasses. The partial solubility parameters of .delta.d and .delta.s of cefalexin were determined to be 8.3, and 10.2 cal1/2/cm3/2 for the crystal and 9.6, and 15.6 cal1/2/cm3/2 for the amorphous, respectively. The solubility parameters were well correlated with the apparent saturated concentration of cefalexin.

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