Simultaneous measurements of solute concentration and Henry's constant using multiple headspace extraction gas chromatography

This study conducted the first experimental work using multiple headspace extraction (MHE) gas chromatographic (GC) techniques to achieve measurement automation in the measurements of solute concentration and vapor-liquid equilibrium partitioning. The study also presented the successful development of a new, accurate MHE GC method to simultaneously measure the concentrations and Henry's constants of solutes in infinitely diluted solutions. Mathematical precision analysis indicates that the phase ratio beta is the key parameter that dictates the accuracy of the MHE GC methods. The precision analysis and experimental verifications indicate that the present method is accurate over a wide range of beta. Good agreement of measured methanol concentration in nine environmental samples using the present MHE method and an indirect headspace GC method were obtained. The measured Henry's constants of 2-propanol and ethanol in water solutions agree with those reported in the literature.