Presentation Profile
Improving identification of Aromatics in Detailed Hydrocarbon Analysis of Gasoline Sample by simultaneous processing of FID and MS signals.
Currently Scheduled: 10/13/2021 - 8:00 AM - 8:25 AM
Room: Daffodil Room
Main Author
Joaquin Lubkowitz - Separation Systems
Abstract:
The analysis of aromatics in gasoline is of major importance for the calculation of the particle index (PMI) as described by Jetter et al.1 This calculation requires the correct identification of aromatics since they are responsible for 95 % of the total PMI of a gasoline. The PMI index is calculated using the double bond equivalence, the vapor pressure, and the concentration of gasoline components. Commonly, the methods used for determining the aromatics and the PMI index are ASTM methods such as ASTM D5769 and ASTM D6730. The former method utilizes only GC-MS analysis while the latter method utilizes only GC-FID analysis. Peak identification in FID chromatograms processed by commercial software is based on Kovats retention indices or pattern recognition algorithms. The splitting of column eluate between the MSD and FID has been well documented.2,3 By adjusting the length of the capillary tubing directed to the MSD and FID, it is possible to reduce the retention time variation of a component between the two detectors to a maximum of ± 4 seconds. In other words, the retention time of the signal generated by the MSD does not vary more than 4 seconds from the retention time of the signal generated by the FID. This fact presents the opportunity to simultaneously display the total ion chromatogram (TIC), selected ion chromatograms, a reference chromatogram, and the FID signal in relative alignment for a single peak on one screen. Selecting and isolating 3 - 4 common ions for each type of aromatic compound allows a comparison of the MSD signal with the FID signal and effective corroboration of the aromatic identity of the FID detected compound. The stark contrast of the MSD peak with its underlying selected ions overlapping the named FID peak identified by retention index facilitates the easy confirmation of the aromatic identity of the evaluated component.
