抄録
A simple method for detection and identification of alkylbenzenes was attempted for gasoline, kerosine and industrial grade alkylbenzene mixtures by using GC/CIMS. About 1 μl of each sample was introduced into a Finnigan 4023 GC/MS/DS equipped with an OV-101 capillary column (0.28 mm i. d. ×20 m or 0.25 mm i. d. ×50 m). Methane was used as a reagent gas. The ion source pressure and temperature were maintained at 0.20 Torr and 250°C, respectively. The mass fragmentograms were recorded at the 20-25 characteristic masses, as m/z 79, 91, 92, 93, 105, 106, 107, 119, 121, 133, 135, 147, 149, 161, 163, 175, 177, 189, 191, 203, 217, 231, 245, 259, 273, corresponding to quasi-molecular ions, (M±H)+, molecular ions, M+, fragment ions, (M-CmHm-1)+ and ions formed by olefin displacement reactions, (M-CmH2m-1)+. The alkylbenzenes were detected selectively by this technique for the sample of gasoline and kerosine. Reconstructed ion chromatogram which was obtained by summing up all of the mass fragmentograms contained only the signal of the alkylbenzenes. Although the identification of each alkylbenzenes was difficult, the estimation of the molecular weights was much easier by CI than EI for the sample of industrial alkylbenzene containing branched chain type compounds. Each alkylbenzene could be identified completely in a sample containing straight chain type compounds. In general, it was found that the compounds of C7H8 to C10H14 were possible to be identified by mass fragmentography without the standard samples. For alkylbenzenes of C11H16 and later ones, the estimation of the molecular weights and the classification of groups of isomers were possible by the present method. For example, they were pentylbenzene, methylbutylbenzene…… pentamethylbenzene in the case of C11H16.
