Elution order in gas chromatography

Abstract

The retention behavior of a heterogeneous group of solutes has been examined on seven different stationary phases under isothermal and temperature-programmed conditions. Both AH, (enthalpy of solute vaporization from the stationary phase) andAS, (entropy of solute vaporization from the stationary phase) valbes were determined for each solutestationary phase combination under isothermal conditions. Both program rate and carrier gas velocity were shown to affect solute elution order. Unless these and other experimental factors discussed are controlled, column equivalency studies based on solute elution order have dubious value.

How the polarity of the separation column may influence the characterization of compost organic matter by pyrolysis-GC/MS

“…PS1 is observed at the beginning of the chromatogram, where many other peaks are coeluted. On a non-polar phase, the separation is mainly based on molecular mass, and few interactions occur between the analyte and the phase [19], while on the polar column, these molecules interact with the wax phase [19] and are better separated. With the non-polar column, compounds are mainly separated according to their boiling point, and starting the GC oven temperature at 30 8C is, thus, too high to avoid the elution of the small polar molecules at the very beginning of the chromatogram.…”

“…Analytes tend to elute in boiling point order ( [19] and references therein). On polar stationary phases, chemical interactions (e.g.…”

“…On polar stationary phases, chemical interactions (e.g. dipole-dipole interactions) occur between solutes and polar groups of stationary phases, increasing retention and selectivity [19]. On wax phases, containing hydroxy groups, hydrogen-bonding interactions may also occur with some analytes.…”

“…The choice of the chromatographic conditions may, thus, drastically change the chromatographic trace of a given pyrolysate, by favoring the separation of certain classes of organic compounds against others. Generally, non-polar stationary phases are more suitable for non-polar analytes, while polar stationary phases are recommended for polar analytes [19].…”

Selectivity vs. polarity: The fundamentals of chromatographic separation

“…This is purely a property of the stationary phase. Selectivity additionally incorporates all interactions of the stationary phase with a given solute functionality, including dispersion, dipole, hydrogen bonding, and any other solute-stationary phase interactions affecting the net vapor pressure of the solute under the chromatographic conditions [4,5]. It is this difference in selectivity that can account for a number of interesting observations.…”