Gas chromatographic analysis of complex hydrocarbon mixtures

Abstract

Kerosene fractions containing a wide variety of homologues and isomers of hydrocarbons of different types and complexities could be analyzed by gas chromatography on a squalane-coated open tubular column (50 m × 0.20 mm). The presence of unsaturated and saturated compounds up to a retention index ( I) of 1150 was ascertained by using a mercury perchlorate post-subtraction column (1 ft. × 1 8 in. O.D.) in series with an open tubular column, which could give only a tentative identification. The temperature dependence of the retention indices ( d I d T ) and the differences in retention indices on polar and non-polar phases (Δ I) have been considered as the basis of an extension of the Kováts retention index system, and this method of peak characterization of kerosene fractions has been investigated. SE-30 was used in a non-polar analytical column and I values were obtained at five isothermal column temperatures ranging from 130° to 170° in order to determine d I d T values for all the peaks. For the determination of Δ I values, tetracyanoethylated pentaerythritol was used in a polar analytical column. Positive and unambiguous characterization of the peaks has been made possible by using the above technique. The limitations of the present methods are discussed critically and schemes are suggested for improved analyses of complex hydrocarbon mixtures.