Liquid penetration as a method of assessing the wettability and surface energy of pharmaceutical powders

Abstract

Abstract The use of a liquid penetration technique to assess the wettability and surface energy of a series of barbiturates, including the use of bicomponent systems, has been critically evaluated. Values of apparent contact angles (θ) obtained using the Washburn relationship (1921) and the Carli & Simioni correction (1979) were found to reflect the practically derived wettability of the powders. Values of γc obtained from modified Zisman plots and from Neumann's equation of state did not realistically describe the surface energies of the powders. The nature of alcohol-water mixtures has been examined to assist elucidation of the theoretical problems associated with the technique and to offer a possible explanation for the inadequacies of the surface energy results.