1995 Volume 44 Issue 4 Pages 277-282
Selective detection and qualitative identification of sulfur compounds in gasoline were carried out by means of a gas electrode detector developed in our laboratory, which uses a sulfide electrode as sensor. Compounds in the sample are separated on a gas chromatographic capillary column using hydrogen as carrier gas. The components eluted from the column are passed through a silica pyrolysis tube (40 cm×0.4 mm i.d.) packed with silica wool and heated at 940°C By this treatment, sulfur compounds can be converted to hydrogen sulfide and hydrocarbon compounds to methane. The decomposition gases are blown upon a hand-twisted cotton thread which is in contact with the sensitive surface of the sulfide electrode. The absorption solution, pH 12.7, containing 0.1 M NaNO3 and 0.05 M NaOH flows (7 μl/min) through the cotton thread, where the hydrogen sulfide is dissolved in the absorption solution. The potentiometric output of the ionselective electrode is digitized and transferred to the microcomputer system. About 0.5 μl of gasoline containing 0.01 % (w/w) sulfur was injected without pretreatment such as extraction or enrichment. Thiophenic compounds were distinguished from nonthio phenic compounds by the difference in their thermal stability in silica pyrolysis tube, the retention time serving as a marker for qualitative identification. Nine sulfur compounds were identified. These include thiophene, dimethyl disulfide, 2-methylthiophene, 3-methylthiophene, ethyl methyl disulfide, 2, 5-dimethylthiophene, 2-ethylthiophene, diethyl disulfide, 2, 3-benzothiophene.
