See more from this Session: Soil Minerals and Human Health: II/Div. S09 Business Meeting
Tuesday, November 2, 2010: 1:30 PM
Long Beach Convention Center, Room 202C, Second Floor
Smectite-rich bentonites can be used in aflatoxin-contaminated feeds or diet to reduce toxicity of the mycotoxin. The objectives of this study were to investigate the bonding mechanism between adsorbed aflatoxin B1 molecules and smectite based on experimental data and molecular mechanic computation. The afaltoxin-smectite complex was synthesized using water as solvent and interlayer adsorption was confirmed with variable-temperature XRD. The stretching vibrations of the two carbonyl bonds of aflatoxin B1 had greater than 22-cm-1 red shifts after being adsorbed to Ca-smectite. At nearly 0% humidity, the C=O vibrations in the monovalent cations K- or Na-saturated complexes located more than 30 cm-1 higher than those in the transition heavy metal Ni-, Mn- or Cu- saturated complexes. Geometry optimization and theoretical IR spectra for aflatoxin and aflatoxin-smectite complexes were performed with density functional theory (DFT) at PCM/B3LYP/DGDZVP level of theory. The experimental spectra were in excellent agreement with theoretical calculations. The calculation allowed accurate assignments of the bands of experimental spectra. We concluded that the major bonding forces were ion-dipole interactions and coordinations between the exchangeable cations and the carbonyl groups of aflatoxin B1 under dry condition, and H-bonding between the carbonyl group and water in the hydration shell of the exchange cations under wet condition.