Adsorption and Desorption of N-Methyl 8-Hydroxy Quinoline Methyl Sulfate on Smectite and the Potential Use of the Clay-Organic Product as an Ultraviolet Radiation Collector

M. A. Vicente, M. Sánchez-Camazano, M. J. Sánchez-Martín, M. del Arco, C. Martín, V. Rives and J. Vicente-Hernández
Instituto de Recursos Naturales y Agrobiología de Salamanca Consejo Superior de Investigaciones Científicas Apartado 257, 37080-Salamanca, Spain
Departamento de Química Inorgánica, Universidad de Salamanca Facultad de Farmacia, 37007-Salamanca, Spain
Departamento de Química, Facultad de Ciencias Universidad Autónoma, Madrid, Spain

Abstract: The interaction between N-methyl 8-hydroxy quinoline methyl sulfate, a drug that absorbs erymathogenic near-ultraviolet radiation, and smectite was studied by X-ray powder diffraction (XRD) and adsorption and desorption techniques. From the adsorption studies, (1) the amount of the drug adsorbed by Na-smectite increased with the pH of the solution to pH 6.5 and then decreased as the pH was further increased; (2) the maximum amount adsorbed at pH 6.5 was 102 meq/100 g of clay; and (3) the maximum amount of drug adsorbed, according to the adsorption isotherms at pH 4, was close to the cation-exchange capacity of the smectite (80 meq/100 g). The XRD studies showed that the drug molecules were adsorbed in the interlayer space of smectite and that cation exchange was the chief mechanism responsible for these interactions. The results of the adsorption-desorption cycles of the drug by smectite showed that this clay is a good support for this compound. In addition, an alternative method was developed to obtain the intercalation compound to avoid the standard method of exchange by impregnation. The method consisted of grinding a mixture of the drug with the clay. The characteristics of the complex thus formed were similar to those of the complex formed by exchange at pH 4 to 7.

To gain insight into the pharmacological properties of the intercalation compound studied, its capacity for absorption of visible and near-ultraviolet light was investigated. The diffuse reflectance spectrum of the complex showed intense absorption bands, absent or weak in the spectra of the pure drug or the untreated clay, at 250, 290, and ∼390 nm.

Key Words: Adsorption • Cation-exchange capacity • N-methyl 8-hydroxy quinoline methyl sulfate • Pharmaceutical • Smectite • Visible-ultraviolet spectroscopy

Clays and Clay Minerals; April 1989 v. 37; no. 2; p. 157-163; DOI: 10.1346/CCMN.1989.0370207
© 1989, The Clay Minerals Society
Clay Minerals Society (www.clays.org)