5.1 The aromatic hydrocarbon content of motor diesel fuels is a factor that can affect their cetane number and exhaust emissions.

5.2 The United States Environmental Protection Agency (USEPA) regulates the aromatic content of diesel fuels. California Air Resources Board (CARB) regulations place limits on the total aromatics content and polynuclear aromatic hydrocarbon content of motor diesel fuel, thus requiring an appropriate analytical determination to ensure compliance with the regulations. Producers of diesel fuels will require similar determinations for process and quality control. This test method can be used to make such determinations.

5.3 This test method is applicable to materials in the boiling range of motor diesel fuels and is unaffected by fuel coloration. Test Method D1319, which has been mandated by the USEPA for the determination of aromatics in motor diesel fuel, excludes materials with final boiling points greater than 315 °C (600 °F) from its scope. Test Method D2425 is applicable to the determination of both total aromatics and polynuclear aromatic hydrocarbons in diesel fuel, but is much more costly and time consuming to perform.

5.4 Results obtained by this test method have been shown to be statistically more precise than those obtained from Test Method D1319 for typical diesel fuels, and this test method has a shorter analysis time.3 Results from this test method for total polynuclear aromatic hydrocarbons are also expected to be at least as precise as those of Test Method D2425.

1.1 This test method covers the determination of the total amounts of monoaromatic and polynuclear aromatic hydrocarbon compounds in motor diesel fuels and blend stocks by supercritical fluid chromatography (SFC). The range of aromatics concentration to which this test method is applicable is from 1 % to 75 % by mass. The range of polynuclear aromatic hydrocarbon concentrations to which this test method is applicable is from 0.5 % to 50 % by mass.

1.2 This test method includes relative bias for Test Method D5186 versus Test Method D1319 and Test Method D6591 versus Test Method D5186 for diesel fuels. The applicable ranges of the correlation ranges are presented in the Relative Bias section. The correlations are applicable only in the stated ranges and only to diesel fuels.

1.3 This test method and correlations were developed for diesel samples not containing biodiesel; the presence of biodiesel will interfere with the results. The correlation equations are only applicable between these concentration ranges and to diesel fuels that do not contain biodiesel.

1.4 The values stated in SI units are to be regarded as standard. The values stated in inch-pound units are for information only.

1.5 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 establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.