Abstract:

A test method for the determination of oxygenates and anilines in motor gasoline was established using a gas chromatograph (GC) with heart-cut accessories and two chromatographic columns. A nonpolar DB-1 column (30 m×0.32 mm×1.0 μm) was used as the pre- column and a polar GS-OxyPLOT or CP-Lowox column (10 m×0.53 mm×10 μm) was used as the analysis column. In a test run, the gasoline sample was first separated according to the boiling points on the nonpolar column. By solenoid valve switching, the compounds of boiling points below 2-hexanone were cut to the GS-OxyPLOT or CP-Lowox column, whereas the other compounds were put through a restrictor to a flame ionization detector (FID). The oxygenates were separated from the hydrocarbons on the GS-OxyPLOT or CP-Lowox column and detected by the FID. When a second run was performed, the solenoid valve switching time was set at the point when m-methyl aniline was all eluted from the nonpolar column into the polar column. Anilines were separated from hydrocarbons and oxygenates on the GS-OxyPLOT or CP-Lowox column. Dimethoxy-ethane was used as the internal standard for quantitation. Methyl tert-butyl ether (MTBE), methanol, methylal, sec-butyl acetate, ethyl acetate, aniline, N-methyl aniline and o/m/p-methyl aniline in motor gasoline were detected and quantitated. The linear ranges were 0.01%-10% (mass fraction) with recoveries of 86.0%-102.6%. The method provides an effective way for quality control of motor gasoline.

Key words: anilines, gas chromatography (GC), heart-cut, methylal, motor gasoline, oxygenates