Effect of the pressure of the carrier gas on the parameters of the Van Deemter equation for monolithic silica gel gas chromatography columns

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Abstract
The chromatographic properties of monolithic capillary silica gel columns for gas chromatography were examined with the use of four different variants of the Van Deemter model. The corresponding experimental curves were measured for the elution of light hydrocarbons with the helium carrier gas in the isothermal mode at 60°C. Despite the models tested are based on different mechanisms of the smearing of chromatographic peaks, the values of the Van Deemter equation parameters proved to be very close to each other for three of the four models. All models yielded negative values of the parameter A. Physically reasonable values of the parameters of the Van Deemter equation were obtained only for the Giddings model, which takes into account the pressure drop across the column. At the same time, this model overestimated the contribution from diffusional smearing (parameter B). It was concluded that none of the models tested adequately described the chromatographic properties of monolithic capillary columns for gas chromatography.