1.1 This test method covers the determination of the purity of methyl tert-butyl ether (MTBE) by gas chromatography. It also provides a procedure to measure impurities in MTBE such as C4 to C12 olefins, methyl, isopropyl and tert-butyl alcohols, methyl sec-butyl and methyl tert-amyl ethers, acetone, and methyl ethyl ketone. Impurities are determined to a minimum concentration of 0.02 mass %. 1.2 This test method is not applicable to the determination of MTBE in gasoline. 1.3 Water cannot be determined by this test method and must be measured by a procedure such as Test Method D 1364 and the result used to normalize the chromatographic values. 1.4 A majority of the impurities in MTBE is resolved by the test method, however, some co-elution is encountered. 1.5 This test method is inappropriate for impurities that boil at temperatures higher than 180°C or for impurities that cause poor or no response in a flame ionization detector, such as water. 1.6 The values stated in SI (metric) units of measurement are preferred and used throughout the standard. Alternate units, in common usage, are also provided to improve clarity and aid the user of this test method. 1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.