Thermodynamically Correct Bioavailability Estimations
Annual rept. 1 May 92-30 Apr 93,
CINCINNATI UNIV OH DEPT OF CHEMISTRY
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The goal of this research is to develop thermodynamically correct bioavailability estimations using chromatographic stationary phases as a model of the interphase system. It has been previously established that octanol-water partition coefficients are not thermodynamically relevant for the modeling of bioaccumulation processes Opperhuizen et al., Environ. Sci Technol. 1988, 22, 286. They investigated the thermodynamic properties of the partitioning of chlorobenzenes between fish lipids and water, and showed that bioconcentration is accompanied by positive enthalpy and entropy changes. In contrast, the partitioning of theses compounds between octanol and water is accompanied by negative enthalpy and by small negative or positive entropy changes. They conclude that the differences in the thermodynamic properties of these processes arise from the different structures of fish lipids and octanol, and that only under very specific conditions and only for structurally similar compounds can a relationship between octanol-water partitioning and bioaccumulation be expected. We have spent the past eight years investigating the molecular mechanism of retention of reversed phase liquid chromatology RPLC, and have shown that at sufficiently high bonded chain density, partitioning of solutes to reversed phase chromatographic stationary phases match the partitioning thermodynamics between fish lipids and water measured by Opperhuizen.