CHARACTERIZATION OF MICROPACKED ALKYL-BONDED SILICA COLUMNS FOR GAS-CHROMATOGRAPHIC ANALYSES OF LIGHT-HYDROCARBONS IN PLANETARY-ATMOSPHERES

Micropacked columns of different types of chemically bonded n-octyl- and n-octadecyl stationary phases were prepared and evaluated for the separation of light hydrocarbons under isothermal conditions. Column selectivities and efficiencies varied with surface coverage and the functionality of the silanizing agents. As might be expected, solute retentions are higher on the C-18 phases than on the C-8 phases due to the increased effective interactive surface between the solute and the stationary phase. Among the phases examined, the polymeric n-octadecyl packings gave the highest plate number and better retention characteristics for the test solutes. The H versus (u) over bar plots obtained revealed the applicability of the columns for fast analysis at low linear carrier-gas velocities and correspondingly low volumetric flow-rates without any substantial loss in efficiency. Within the temperature range investigated, thermal-stability experiments indicate that the polymeric n-octadecyl phase can be used at temperatures up to 250 degrees C with little or no column bleed.