SPECIFIC INTERACTIONS AFFECTING GAS CHROMATOGRAPHIC RETENTION FOR MODIFIED ALUMINA COLUMNS

The gas chromatographic retention of hydrocarbons has been studied on salt-modified aluminas. The results establish that the retention volume is dependent upon a composite of nonspecific and specific adsorptive interactions. The latter includes effects due to the pi character of the sample molecule and to its planarity. For aromatic hydrocarbons, substituent groups affect the gas-solid interactions, and for olefins the cis isomer is retained more strongly than the trans isomer. A quantitative evaluation of these effects and of different modifying salts permits the design of columns for the selective separation of cistrans isomers and of mixtures containing paraffinic, olefinic, and aromatic hydrocarbons with similar boiling points. © 1968, American Chemical Society. All rights reserved.