Flux of gases across the air-water interface studied by reversed-flow gas chromatography

In the present work the reversed-flow gas chromatographic technique was app lied for the study of flux of gases across the air-water interface. The mod el system was vinyl chloride-water, which is of great significance in food and environmental chemistry. Using suitable mathematical analysis, equation s were derived by means of which the following physicochemical quantities w ere calculated: diffusion coefficient of vinyl chloride (VC) into water, pa rtition coefficient of VC between the water (at the interface and the bulk) and the carrier gas nitrogen, overall mass transfer coefficients of VC in the gas (nitrogen) and the liquid (water), gas and liquid film transfer coe fficients of VC, gas and liquid phase resistances for the transfer of VC in to the water, and finally the thickness of the stagnant film in the liquid phase, according to the two-film theory of Whitman. From the variation of t he above parameters with temperature, as well as the volume and the free su rface area of the water, useful conclusions concerning the mechanism for th e transfer of VC into water were extracted. These are discussed in comparis on with the same parameters calculated from empirical equations or determin ed experimentally by other techniques. (C) 2001 Elsevier Science B.V. All r ights reserved.