Gas Chromatographic Analysis of Polymethyl-Substituted Alkanes

The gas chromatographic analysis of various monobranched alkanes with branches ranging from methyl to pentyl in the C10 to C30+ area was discussed in a previous article. The present article represents an extension of this analysis to multimethyl-branched alkanes in the same carbon atom range. To this end, several mixtures of various branched alkanes were prepared by olefin co-oligomerization and mild thermocracking of high molecular weight isoprenoids. Both these techniques allow prediction of possible structures of multibranched alkanes which facilitates peak assignment in gas chromatograms of the mixtures. Information obtained in the analysis was used for refinement of the additivity principle in gas chromatography of paraffins described by Spivakovskii et al. The resulting computation procedure allows reliable assignment of peaks of various multimethyl-branched alkanes in gas chromatograms of complex hydrocarbon mixtures.