A new gas chromatographic methodology for the estimation of the composition of binary gas mixtures

The relatively new technique of reversed-flow gas chromatography (RFGC) is used to determine the diffusion coefficients of pure gases into gas mixtures (Dexpmix). The pure gases are CO and CO2, and the mixtures consist of H2 and He in various volume percentage compositions. A linear regression analysis of Dexpmix of CO and CO2 in various mixtures of H2 and He against the percentage composition (XH2 or XHe) of the mixtures at different temperatures results in an empirical equation relating Dexpmix to the corresponding theoretical values of the diffusion coefficients of CO and CO2 in the pure gases H2 and He, as they are calculated from the Fuller-Schettler-Giddings equation. The empirical equation shows that the diffusion coefficient of an analyte gas in a gas mixture is the partial sum of its diffusion coefficients in the component gases, therefore making possible the determination of the mole fractions of the components of the mixture. The found percentage volume compositions are very close to those determined independently by routine gas chromatography, indicating that the proposed RFGC methodology could be successfully applied to the accurate determination of the volume composition of binary gas mixtures.