Thermodynamic partitioning behavior for solutes into immobilized artificial membrane or an n-octanol/water system

The thermodynamic partitioning behavior of solutes into immobilized artificial membrane(IAM) and n-octanol/water systems was investigated, including acidic, basic, and amphoteric substances. In an n-octanol/buffer system, partitioning process was entropy-dominated for the most studied drugs, while partitioning of oxolinic and nalidixic acids into n-octanol phase was enthalpy-driven. In IAM chromatography, partitioning into membrane for the studied solutes was enthalpy-driven and an exothermal process. In conclusion, there is a significant difference of solutes' partitioning mechanism into either IAM or an n-octanol phase, therefore, presenting the theoretical basis for differing lipophilicity measuring scale.