Agilent Technologies has produced an application note demonstrating the determination of the olefin content in denatured ethanol using the Agilent 1260 Infinity Analytical SFC system together with the SIM Flame Ionization Detector (FID).
Denatured ethanol is used as an oxygenate additive in spark ignition engine fuel. It is added to fuel at the terminals, and can contain olefinic species, which contribute to the total olefins content. Olefinic hydrocarbons have been demonstrated to contribute to photochemical reactions in the atmosphere. This can result in the formation of smog in susceptible urban areas. Therefore, the California Air Resources Board (CARB) has specified a maximum allowable limit of total olefins in spark ignition engine fuel.
An analytical method is necessary to determine the amount of olefins in denatured ethanol intended for spark ignition engine fuel, as described in ASTM method D7347-07. In this application, it is shown that the SFC/FID system meets all requirements of ASTM D7347-07. The test method is automated, does not require any sample preparation, and has a relatively short analysis time of approximately 10 minutes. The application range is from 0.1 to 1.0 mass% total olefins. For the final method, the retention time (RT) and area precision, the accuracy of olefin quantification, and detector linearity is demonstrated. Finally, a denatured ethanol sample is measured.
Results and Discussion
This ASTM D7347 test method for the determination of the total amount of olefins in denatured ethanol is based on a chromatographic SFC LC system with three columns and two six-port switching valves. Step by step, the olefins are separated from ethanol, aromatics, and saturates; an FID is used for quantification of the olefins.
This application note demonstrates the improved capabilities of the Agilent 1260 Infinity Analytical SFC system in combination with the SIM/FID for the determination of olefins in denatured ethanol according to ASTM D7347-07. Combining the 1260 Infinity Analytical SFC system with this FID meets all requirements of the ASTM D7347‑07 method such as the required retention time precision for time‑based column switching, good area precision, and calibration function.