The silica gels were chemically treated with several kinds of alcohol or with tartaric acid dibutyl ester. Most of the surface silanols on these silica gels were confirmed to be substituted by the corresponding alcoxy group of the alcohol used or by tartaric acid diester group by means of their ir-spectra and the number of surface group estimated from the results of the microanalysis. Both original and surface-treated silica gels were used as the supports to investigate the gas chromatograph. The solutes used were the isomer of dimethyl cyclohexane, the mixture of n-heptane, n-hexene and benzene and the mixture of cyclohexane, cyclohexane and benzene. The following results were obtained:
(1) The gas chromatograph using the original silica gels showed an appreciable tail in the shape of peak and a long retention time. These were attributed to the strong interaction between the surface silanols and solutes.
(2) The gas chromatograph using the silica gels treated with linear chain alcohols showed that the longer carbon chain (increasing hydrophobic nature) causes more effective separation of the solutes mixture and symmetric shape of the peak. These were attributed to the low energy surface of these supports.
(3) The silica gels with the surface group containing the hydrophilic functional groups such as _??_C=O and _??_C=O-O- dispersed well into water, and showed hydrophilic nature. However, in the gas chromatograph of the mixture of the non-polar solutes these supports behaved like the ones with low energy surface (symmetric peak shape and the short retention time.). The heat of adsorption obtained from the plots of logtR/T against 1/T supported these results.
