Applications of the octanol–air partitioning ratio: a critical review

Abstract

The octanol–air partition ratio (K_OA), also referred to as the octanol–air partition coefficient, has a wide range of applications in environmental chemistry. In this review, we explore the historical context of using octanol as a surrogate for various types of organic matter. We examine in detail the single-parameter linear free energy relationships (spLFERs) that rely on the K_OA to describe partitioning equilibria between the gas phase and vegetation, soil, particles, dust, surfaces, materials, and animal tissues. We further use poly-parameter linear free energy relationships (ppLFERs) to estimate how well octanol approximates the partitioning properties of these divergent phases. While the availability of ppLFERs for many environmentally and biologically relevant phases has rendered some of the spLFERs based on the K_OA largely obsolete, the K_OA still serves a useful purpose as a single parameter describing the tendency of a neutral organic chemical to partition from the gas phase into a wide variety of organic phases. As such, it is a well-defined, easy-to-comprehend and experimentally accessible descriptor of compound volatility from organic phases.