An Experimental and Computational Study of the Loading and Release of Aspirin from Zeolite HY

The anti-inflammatory drug, aspirin, was loaded into three zeolite FLY hosts with silica to alumina ratios (SiO2/Al2O3) of 5, 30, and 60. The aspirin loading in the zeolite HY samples as measured by thermogravimetric analysis decreased from 106, to 78, to 69 mg aspirin/g zeolite with increasing SiO2/Al2O3. The surface areas and pore volumes, measured using nitrogen adsorption-desorption experiments, indicated that the aspirin was loaded into the internal pore surface of these materials. The Fourier transform infrared and Al-27 and C-13 magic angle spinning nuclear magnetic resonance spectra of the aspirin-loaded materials provided molecular level information about aspirin-zeolite interactions. Quantum calculations at both Hartree-Fock and density functional theory levels of theory were conducted in order to understand the nature of intermolecular interactions between the zeolite host and the aspirin. The release of the aspirin from FLY was dependent on the hydrophobicity of the zeolite host with more hydrophobic zeolites (higher SiO2/Al2O3) releasing the aspirin less readily.