EXPLANATION
Fuel ethanol is required to be denatured with gasoline in accordance with Specification ASTM D4806. State and federal laws specify the concentration of ethanol in gasoline blends. Hence, the determination of the amount of denaturant is important. This test method covers the determination of ethanol content of denatured fuel ethanol by gas chromatography. Ethanol is determined from 93 to 97 mass %, and methanol from 0.1 to 0.6 mass %. This test method does not identify and quantify methanol but does purport to identify all individual components that make up the denaturant. Water cannot be measured by this test method, but can be measured by procedure such as Test Method ASTM D1364. The result would be used to correct the chromatographic values. This method is inappropriate for impurities that boil at temperatures above 225° C, or for impurities that cause poor or no response in a flame ionization detector, such as water.
TEST SUMMARY
A fuel ethanol sample is injected into a gas chromatograph equipped with a methyl silicone bonded phase fused silica capillary column. Helium carrier gas transports the vaporized aliquot through the column where the components are separated. They are detected by a flame ionization detector as they elute from the column. The detector signal is processed by an electronic data acquisition system. The identification of all components is done by comparing their retention times with those of standards, and concentration is calculated by using normalized peak areas.
TEST PRECISION
Where X is the mass percent. The range is given in mass percent.
No significant difference was found between the ethanol or methanol content obtained by this test method and the expected content based on their concentration added to the samples.