C. del Hoyo

Thermal studies of pharmaceutical-clay systems Part I. Montmorillonite-based systems

Abstract Pharmaceutical-clay systems, used as solar radiation shields, obtained by interaction of Na montmorillonite and several pharmaceuticals using two methods of preparation, have been studied. Samples have been prepared by melting the drug onto the clay or by intimate mixing and grinding of both. The shielding ability against solar radiation is improved by use of these preparation methods. Differential thermal analysis and thermogravimetric analysis confirm the steady substitution of water molecules from the interlayer space of the clay by drug molecules, as the amount of the latter is increased. The melting method seems to facilitate access of the drug into the interlayer space of the clay.

Thermal studies of pharmaceutical clay systems. Part II. Sepiolite-based systems

Pharmaceutical-clay systems, used as solar radiation shields, obtained by interaction of natural sepiolite and several pharmaceuticals using two methods of preparation (melting the drug onto the clay or by intimate mixing and grinding of both), have been studied. The shielding ability against solar radiation is improved by using these preparation methods. Differential thermal analysis and thermogravimetric analysis confirm displacement of water molecules adsorbed onto the clay surface by the pharmaceutical molecules. The grinding method seems to facilitate adsorption and dispersion of the drug onto the clay surface.

Interaction of N-methyl 8-hydroxy quinoline methyl sulphate with sepiolite

Abstract The adsorption of N-methyl 8-hydroxy quinoline methyl sulphate—a drug generally used to protect from sunburn—by natural and acid-treated sepiolite, has been investigated. Acid treatment led to partial dissolution of the fibres of the clay, mainly in the external surface of the crystallites. Incorporation of the drug decreased the amount of water adsorbed, leading to a strong interaction between the drug and the clay, but upon acid treatment the interaction seemed to weaken. Clay-drug complexes formed by adsorption from the drug aqueous solutions and by mechanical mixing of the components in the solid state served as good sunburn shields, as indicated by the spectra of these materials in the visible-ultraviolet range of the spectrum.

Application of Methyl Cinnamate/Montmorillonite as Ultraviolet Radiation Shelters

AbstractThe interaction of methyl cinnamate/montmorillonite samples prepared by melting the former onto the second or by joint grinding, has been studied by x-ray diffraction. differential thermal analysis, thermogravimetric analysis and Fourier-transform infrared spectroscopy. Formation of an interlayer compound has been observed, leading to an increase of 4.15 or 3.42 A (samples obtained by melting or grinding, respectively) in the basal spacing of the clay. Formation of such a complex leads to a displacement of molecular water from the interlayer space, as concluded from the thermal studies. No chemical change is observed in the methyl cinnamate molecule, as confirmed by infrared spectroscopy. The system prepared improve the shelter properties of the clay and the drug separately, mainly in the C zone of the ultraviolet spectrum (290-190 nm).

Electronic Spectra of Phenyl Salycilate/Montmorillonite and Sepiolite Complexes Obtained by Grinding and Melting

Abstract Grinding or melting of phenyl salycilate on montmorillonite and sepiolite leads to adsorption complexes suitable to prevent sun-burning by UV radiation. The protecting ability of the pure drug or of the clays are improved upon dispersion of the former onto the surface of the clays, specially in the 290–190 nm range.

Electronic Spectra of N-Methyl 8-Hydroxy Quinoline Methyl Sulphate Adsorbed on Sepiolite

Abstract Adsorption of the drug N-methyl 8-hydroxy quinoline methyl sulphate, used to prevent sunburning and to avoid the dangerous effect of erythematogenic radiations, on untreated and HCl-treated sepiolite has been studied. The adsorption complex formed extends the absorption properties of the drug in the visible and ultraviolet range. The behaviour shown by these samples is fairly similar in all cases with respect to light absorption. However, adsorption complexes prepared via a dry method, by mechanically mixing the drug and sepiolite, lead to samples with different light absorbent properties, due to the modification of the surface acid/base properties of the sepiolite and hence of the way the drug is adsorbed.

Selective oxidation of methanol on V2O5 and V2O5−MoO3 supported on montrmorillonite

Methanol oxidation on V2O5 and V2O5−MoO3 catalysts supported on montmorillonite has been studied in the temperature range of 250–500°C. The V2O5−MoO3 containing sample shows higher selectivity towards formaldehyde formation than the V2O5 catalyst.