A preliminary study on the analysis of methane and ethylene by gas chromatography flame ionization detection (GC‐FID) following the sampling by gas permeation through a polymer membrane

Abstract A lab‐fabricated permeation system hyphenated to a gas chromatograph with a flame ionization detector was used to examine the analysis of methane and ethylene. Various concentrations of methane and ethylene in a single or mixture were injected into the permeating chamber containing high‐purity nitrogen or helium atmosphere. The penetrated gases through a poly(ethylene‐ co ‐vinyl acetate) membrane were flushed into a GC–FID equipped with a Porapak packed column for separation and detection using N 2 or He carrier gas. The permeation processes of CH 4 and C 2 H 4 reached a steady state after 10 min. Since this “lag time”, the amounts that penetrated CH 4 and C 2 H 4 were proportional to the permeation time. Within a certain permeation time, the amounts of CH 4 and C 2 H 4 at both sides of the membrane were linearly correlated, facilitating the possibility of quantitative analysis of CH 4 and C 2 H 4 . The permeability coefficients for CH 4 and C 2 H 4 in various permeation conditions were calculated. They showed that the penetration of CH 4 and C 2 H 4 in the He atmosphere was 11 times better compared to the N 2 atmosphere, e.g. the sensitivity of the measurements is also better. This study revealed that permeation through a polymeric membrane could be applied to the analysis of CH 4 and C 2 H 4 or, on a large scale, to the gases or volatile compounds for various applications.