Molecular incorporation of benzoic acid and salicylic acid into BEA zeolites

Purpose: To develop new solid dispersions of benzoic acid (BA) and salicylic acid (SA) using Beta zeolite and to investigate the molecular states of the drugs in the pores. Methods: Zeolites, BEA12.5, BEA150 and Fe-BEA, were used. Solid dispersions of 30%BA or SA-70%BEA were prepared by solvent evaporation and sealed-heating. The molecular state of the drugs was estimated by powder X-ray diffractometry, thermal analysis, FT-IR spectroscopy, and fluorescence spectroscopy. Results: Powder X-ray diffractometry and thermal analysis confirmed that evaporation and sealed-heating treatments caused BA to be adsorbed into the BEA12.5 pores. In addition, SA was confirmed to be adsorbed onto BEA12.5 when the solid dispersion was prepared by solvent evaporation and sealed-heating. Fluorescence spectroscopy of the sealed-heating sample of the BA-BEA12.5 system showed a shift to the long wavelength side region of the emission spectrum observed in BA crystals at 309 nm. Conclusions: It was found that zeolites were useful carriers for the preparation of drug dispersions. Benzoic acid or SA molecules were adsorbed in the BEA12.5 pores monomolecularly or on the surface in a non-crystalline molecular form.

Keywords: Zeolite Solid dispersion Adsorption Molecular interaction