Measurement of Large Infinite Dilution Activity Coefficients of Nonelectrolytes in Water by Inert Gas Stripping and Gas Chromatography

An inert gas stripping gas chromatography method was described for the determination of infinite dilution activity coefficients (γ₂^∞) of organic compounds in water. The infinite dilution activity coefficients for 31 compounds including many halogenated and aromatic compounds were measured. In general, the γ₂^∞ values measured by gas stripping are in very good agreement with γ₂^∞ values estimated from the inverse solubilities and other experimental measurements. This suggests that when there is no directly measured data available, γ₂^∞ values estimated from the inverse of solubility can be used for the development and test of the models predicting limiting activity coefficients. A major advantage of this method relative to headspace gas chromatography that improves its precision and accuracy is the fact that the absolute detector response is unimportant. The detector only needs to be linear.