Determination of Temperature-Dependent Henry’s Law Constant of Four Oxygenated Solutes in Water Using Headspace Solid-Phase Microextraction Technique

Abstract

Dimensionless Henry’s law constants (air/water partition coefficient Kaw) of four volatile organic compounds (VOCs), namely, methyl tert-butyl ether, vinyl acetate, dimethyl carbonate, and diethyl carbonate, are reported. Applying headspace solid-phase microextraction (HS-SPME) in combination with gas chromatographic analysis, whose response was calibrated by the use of standard gas mixtures, Kaw values (0.001 < Kaw < 0.1) were determined in the temperature range of (10 to 45) °C. Replicated measurements showed a good repeatability (average relative standard deviation 2.5 %, n = 144). The results were checked through additional Kaw measurements carried out using the inert gas stripping (IGS) technique at 25 °C, receiving intermethod deviations < 5 %. Furthermore, approximate values of hydration enthalpies ΔHhyd and hydration entropies ΔShyd for the four VOCs were derived from linear van’t Hoff fits of the Kaw(T) data, demonstrating an enthalpy-driven partition process.