Determination of Elemental Sulfur in Naphtha and Gasoline by Gas Chromatography/Mass Spectrometry

Abstract

Trace elemental sulfur, S0, in naphtha and gasoline seriously affects the quality of naphtha and gasoline. It is difficult to analyze the contents of trace elemental sulfur because of their low concentrations. Presently, the S0 contents are usually determined by polarography, but the practical use of this method is limited because of some interference factors. In this work, S0 structure in naphtha and gasoline was studied through many experiments by gas chromatography/mass spectrometry (GC/MS) and S0 is mainly present as S8. A new analytical method for S0 determination in naphtha and gasoline using GC/MS was developed. The S0 was analyzed through selected ion monitoring (SIM) and quantitative determination was achieved through an external standard method. One microliter of sample oil was directly injected and analyzed by GC/MS within 16 min. In comparison with the existing method for S0 determination, this technique was found to be much simpler, faster, more sensitive and interference-free. Good correlation coefficients (> 0.9995) for the S0 calibration curves were obtained in the concentration range of 0.01 mg/L–100 mg/L by using appropriate GC/MS parameters. The absolute limit of detection of this method was 9.55 pg and the precision relative standard deviation (RSD) was usually better than 5% and the recoveries were 93.01–106.21%. The method was used successfully in the determination of S0 in naphtha and gasoline samples collected in Jiujiang Refinery and it had great application prospects. In addition, this technique required only a very small sample size to perform a good analysis, which was an important advantage for studies where sample size was restricted.