Effects of micropores on peak shape and retention volume in gas-solid chromatography

Abstract

A high-precision gas chromatograph has been used to study porosity effects by comparing the elution behavior of methane, ethane, and isobutane on 4A and 5A molecular sieves. Methane and ethane, which could enter the sieve crystallites, showed tailing independent of sample size. For the first time in gas chromatography, changes in retention volume were observed with changes in flow rate. Furthermore, methane and ethane showed a pronounced decrease in column efficiency with increasing temperature in the mass-transfer limited region rather than an increase. Those effects were attributed to slow diffusion within the zeolite because isobutane, which was excluded from the zeolite pores, did not show those effects.

A Physicochemical Study of Polypyrrole–Silica Nanocomposites by Inverse Gas Chromatography

“…[7] The number of methyl groups per alkane (n CH 3 ) was used as an empirical steric hindrance parameter to characterize the materials. Figure 8 shows a plot of D(DH a ) versus n CH 3 for the various C 7 alkane isomers.…”

Computer-controlled gas chromatograph capable of real-time readout of high-precision data

“…Images are produced from the best available original document. and their utility has been well demonstrated (3)(4)(5)(6)(7). However, both of those instruments dre limited by the fact that the highprecision results must be calculated using an off-line digital computer.…”

Chromatographic Behavior of a Cholesteryl Myristate Stationary Phase in an Electric Field

“…Finally, the integration limits and the number of data points obtained across a peak can al€ect the observed accuracy (36). The requirement of a finite cutoff in the data can, in some cases, impose a fundamental restraint on the interpretation of the center of gravity (38 41) and may affect the observation of nonequilibrium phenomena such as flow-dependent retention volumes (38,(41)(42)(43)(44).…”