Multi-media partitioning properties play a crucial role in determining contaminant fate, transport, exposures and ultimately toxic effects. In 1802 William Henry reported the first measurements of air-water partition coefficients in the form of Henry's Law constants. 200 years of empirical investigations and theoretical developments followed to establish databases of partition coefficients for a multitude of chemicals between environmental and biological phases, resulting in a wide range of correlations, QSARs, QSPRs and LFERs for explaining and predicting partition coefficients, especially employing n-octanol as a surrogate for organic phases. A major incentive was to understand and predict narcosis, which led to extensive empirical data, valuable insights and increasingly effective and available predictive methods. Theoretically sound criteria such as chemical potential, fugacity and activity emerged to describe the equilibrium partitioning of solutes, especially chemical pesticides and contaminants, between environmental and biological phases. Reliable partitioning data employed in mass balance models explained, simulated and predicted chemical fate in the environment and in organisms, contributing to more enlightened management and regulation of chemicals of commerce. Recent advances are discussed leading to conclusions that there is a continuing need for (i) development and evaluation of a range of predictive methods from simple easy-to use QSARs to computationally intensive molecular models, (ii) meticulous measurements of fundamental chemical properties to �ground truth� predictions, especially for �emerging� contaminants, degradation products and metabolites, (iii) improved methods of communicating the importance of partitioning properties for chemical stewardship and �green chemistry� and (iv) exploiting equilibrium criteria of fugacity and activity in mass balance models to simulate and interpret chemical fate, exposure and toxicity in environmental and biological systems.

Perspective on the evolution and future of partition coefficients

246th National Meeting (2013)

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