Significance and Use 5.1 A knowledge of the hydrocarbon composition of the middle distillates, including the biodiesel blends is useful in following the effect of changes in process variables, diagnosing the source of plant upsets, and in evaluating the effect of changes in composition on product performance properties. The total aromatics content and polycyclic aromatics content are also important to evaluate the quality of diesel fuels/biodiesel blends. It requires an appropriate analytical method to make such determinations for diesel fuel/biodiesel blends production process and quality control. 5.2 This test method provides a comprehensive analytical strategy for the determination of the total aromatics contents, polycyclic aromatics contents and the detail hydrocarbon composition of diesel fuel/biodiesel blends to ensure compliance with certain specifications or regulations. 5.3 Test Method D2425 is applicable to the determination of the detailed hydrocarbon composition in middle distillates, however, the pre-separation procedure of elution chromatography is time-consuming and not eco-friendly. By combining with the separation procedures described in Test Method D8144, the dual column GC-MS system proposed in this method can determine the total aromatic hydrocarbon contents, polycyclic aromatic hydrocarbon contents and detailed hydrocarbon composition of diesel fuel/biodiesel blends simultaneously. The content of FAME in biodiesel blends can also be determined by GC. It is demonstrated to be time-saving and eco-friendly for the quality control of diesel fuel and biodiesel blends.Scope 1.1 This test method covers an analytical scheme using the gas chromatography/mass spectrometry (GC-MS) to determine the hydrocarbon types present in middle distillates 170 °C to 365 °C boiling range, 5 % to 95 % by volume as determined by Test Method D86, including biodiesel blends with up to 20 % by volume of fatty acid methyl ester (FAME). The detailed hydrocarbon composition, total aromatic hydrocarbon and polycyclic aromatic hydrocarbon contents can be determined. The hydrocarbon types include: paraffins, noncondensed cycloparaffins, condensed dicycloparaffins, condensed tricycloparaffins, alkylbenzenes, indans or tetralins, or both, CnH2n-10 (indenes, etc.), naphthalenes, CnH2n-14 (acenaphthenes, etc.), CnH2n-16 (acenaphthylenes, etc.), and tricyclic aromatics. The content of FAME in biodiesel blends can also be determined by GC. 1.2 The values stated in acceptable SI units are to be regarded as the standard. No other units of measurement are included in this standard. 1.3 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. 1.4 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.
