This paper reports the experimentally determined and calculated partition coefficients (Kp) in a heterogeneous system consisting of two partially mixing organic solvents for trimethylsilyl derivatives of 119 compounds including phenols, phenolcarboxylic acids, mono- and dicarboxylic acids, and some carbohydrates and polyols. It was demonstrated that a simple model based on the available physico-chemical properties of molecules can be used to accurately predict the hexane-acetonitrile partition coefficients. Phenols, other organic acids, and carbohydrates form complex mixtures in extracts of plant tissues, in various biological fluids, as well as in waste waters. For group identification of these mixture components, it is desirable to use the parameterj which is a combination of Kp and gas chromatographic retention indices: j = kI - log Kp. This approach increases identification reliability in gas chromatographic analysis. The use of the group parameterj in the analysis of nonvolatile organic components of waste waters is reported.