Application of Cracking Pattern Identification Principle to Gas Chromatography

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  • ASAKURA Yuji
    Department of Chemistry, Faculty of Science, Kyoto University Present address: Institute of Chemistry, Kyoto Prefectural University of Medicine

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  • クラッキング・パターン同定法のガス・クロマトグラフィーへの応用
  • クラッキング パターン ドウテイホウ ノ ガスロ クロマトグラフィー エ ノ オウヨウ

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Abstract

The mass spectroscopic cracking pattern with its rich informations serves as a reliable basis for identification of organic compounds . Identification on the basis of the gas chromatographic retention time alone is much less reliable . If a substance can be converted by a suitable treatment into a mixture of many substances, the mixture will yield a gas chromatogram with n peaks. This gives2-1informations, namely, n retention times plus -1 relative peak areas, thus making identification more reli able. By thermal decomposition by an electrically heated filament, for example, ethylether, methyl-thioether, n-pentane, n-hexane, iso-hexane and cyclohexane gave respectively6, 8, 4, 6, 7, and5peak pyrolysis chromatograms . Effects on these peaks of changes of several experimental conditions were studied. Within the extents of the changes performed, retention times always remained unaffected. The area of each peak of the pyrolysis chromatogram of a substance changed differently with filament temperatures, namely, steady increase, leveling off, decrease through a maximum, or steady decrease. These temperature-dependence curves plotted all on a single graph will reveal a feature especially suitable for identification. This general feature of such a composite graph was found, at least in the case of n-pentane, essentially independent of the filament material(tungsten or platinum)and shape(hair-pin or spiral). With increasing sample size up to9. 3μl. all the five peaks of the pyrolysis chromatogram of cyclohexane increased in area linearly until about7. 3μl. For the same sample size(7μl)of various benzene to cyclohexane ratio mixtures benzene always favored the thermal decomposition of cyclohexane.

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