Fast and Selective Determination of the Gasodor S-free Using Ion Mobility Spectrometer Equipped with Corona Discharged Ionization Source: Theoretical Study, Experimental Optimization and Field Test

The past decade has witnessed a growth of using sulfur-free (S-Free) odorants in the natural gas odorization, but development of the fast, selective, sensitive, and low-cost methods for determination of S-Free odorant con-centration in the gas flow remains as an important issue. In this research, we successfully optimized an ion mobility spectrometer (IMS) equipped with a corona discharged ionization source for the determination of Gasodor S-free odorant in the natural gas. The optimized method can completely prevent the production of the dimers between ethyl acrylate and methyl acrylate and hence, enhancing the sensitivity of the proposed method. In addition, in this method, there is no need to use expensive gas chromatography columns to solve the problem of the overlap between ethyl acrylate and methyl acrylate peaks. The proposed method is able to determine the Gasodor S-free in the natural gas in less than 2 min. The total cost for each analysis is lower than 0.10 USD. The limit of detection (LOD) and the limit of quantification (LOQ) were calculated based on the signal-to noise-ratio of 3 and 10, respectively. The results were 0.46 mg .m(- 3) and 1.56 mg m(- 3) respectively for LOD and LOQ. The relative standard deviation (RSD %) of the results was +/- 2.3 %. In this work, for the first time, Gasodor S-free was applied in the selected area of the Iranian natural gas grid and the practical characteristics such as olfactory tests, variations in the odorant concentration during night and day and optimum concentration of Gasodor S-free were studied and discussed.