Comparison of Helium and Hydrogen Carrier Gases for Analysis of Benzene, Toluene, and Aromatics in Gasoline by GC/MS

Tuesday, March 09, 2021: 1:30 PM - 1:50 PM

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Description

Analysis of benzene, toluene, and aromatics in gasoline is critical to ensure compliance with environmental regulations and ensuring fuel quality. GC/MS is a powerful tool for such analyses by coupling the separations power of a gas chromatograph with the mass-specific detection of a mass spectrometer. Whereas other techniques can provide results for the total aromatic content, GC/MS provides for the definite identification and quantification of the individual components of a fuel. This allows refiners to ensure process efficiency, minimize costs, and comply with regulatory standards. The methodology employed largely follows that in ASTM D5769. The instrument was calibrated in a range that is variable for each compound, but in general the range is from 0.25 to 3 %, with some compounds (benzene, ethylbenzene, xylenes) calibrated about 2 times higher, and toluene calibrated from 1.5 to 18 %. A 0.1 µL of sample was injected into the GC/MS using an AOC-20i at a very high split ratio, allowing for separation on the column. A GCMS-QP-2020NX was used for ionization and mass filtering is performed by a single-quadrupole mass spectrometer. Both helium and hydrogen were evaluated as carrier gases. Good calibration curves for all compounds (r2 values ≥ 0.99) shows the viability of using either helium or hydrogen carrier gas and also the reproducibility of using the AOC-20i with small injection volume. This is especially critical for toluene, as the standard calibration curve provided is at a much higher level than the other analytes. By adjusting the detector voltage to prevent oversaturation at the high level of the calibration, the calibration curve for toluene easily meets the method requirements. Area counts and repeatability for all compounds were similar for both carrier gases. The sample run times using H2 were ~22 minutes, whereas those for He were ~32 minutes. This improves sample throughput and reduces costs of operation.

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Track(s)

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  Energy

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Additional Info

Keywords: Please select up to 4 keywords ONLY:
Mass Analyzers,Fuels/Petrochemical