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Lab Methods

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Oxygenates in Gasoline

  • Method ASTM D4815/ASTM D5599
  • Repeatability variable, see method
  • Reproducibility variable, see method
  • Blending linear
  • Additive Correction No

These test methods cover the determination of ethers and alcohols in gasolines by gas chromatography. Specific compounds determined are methyl tert-butylether (MTBE), ethyl tert-butylether (ETBE), tert-amylmethylether (TAME), diisopropylether (DIPE), methanol, ethanol, isopropanol, n-propanol, isobutanol, tert-butanol, sec -butanol, n-butanol, and tert- pentanol (tert-amylalcohol).

The D4815 method is performed by adding internal standard to a gasoline sample and injecting it into the GC. The gc separates the oxygenates using a special column so that each compound can be identified and then quantified using a calibration table.

D5599 is performed the same way as the above but it uses more complex technology inside the gc. In this method the sample is injected and moves through a similar column. When it reaches the end of this column it enters a reactor that converts any oxygenates in the sample to Carbon Monoxide. This Carbon Monoxide then passes through a methanizer and converts the CO back into the oxygenate Methane. Once complete it will pass through the detector where it is identified and quantified.

The D5599 is a more robust method and is not susceptible to interference like the D4815. Oxygenates are important to the gasoline blenders because of their ability to increase octane values and reduce Carbon Monoxide tail pipe emissions. They must be added in to proper ratios in order to meet compliance standards and ensure proper engine performance/efficiency.