Determination of solid–liquid partition coefficient of volatile compounds by solid phase ratio variation based headspace analysis

Abstract

A novel method has been developed for the determination of the solid–liquid partition coefficient of volatile analytes using headspace gas chromatography (HS–GC). The method is based on the headspace measurement for the three-phase equilibrium in sample vials containing different amounts of solid sample. Theory is presented that allows calculation of partition coefficient of the analyte from the HS–GC data obtained at the condition of solid phase ratio variation (SPRV). Analysis of errors demonstrates that this solid phase ratio variation method generates results with reasonable precision for all volatile compounds, much better than the liquid-focused (i.e., liquid phase ratio variation) method reported early.The solid phase ratio variation method was used to determine the solid–liquid partition coefficient of toluene in a water–polystyrene system, using polymer particles with average size ranging from 0.4 to 2.1μm. The results show that the partition coefficient of toluene in the given system is proportional to the specific surface area of the polymer particles, as expected.In summary, the method is a simple and practical tool for determining the solid–liquid partition coefficient of volatile analytes.