ASTM D6591 Standard Test Method for Determination of Aromatic Hydrocarbon Types in Middle Distillates - High Performance Liquid Chromatography Method with Refractive Index Detection
1. Scope
1.1 This test method covers a high performance liquid chromatographic test method for the determination of monoaromatic, di-aromatic, tri+-aromatic, and polycyclic aromatic hydrocarbon contents in diesel fuels and petroleum distillates boiling in the range from 150 to 400°C. The total aromatic content in % m/m is calculated from the sum of the corresponding individual aromatic hydrocarbon types.
NOTE 1 - Aviation fuels and petroleum distillates with a boiling point range from 50 to 300°C are not determined by this test method and should be analyzed by Test Method, D6379 or other suitable equivalent test methods.
1.2 The precision of this test method has been established for diesel fuels and their blending components, containing from 4 to 40 % (m/m) mono-aromatic hydrocarbons, 0 to 20 % (m/m) di-aromatic hydrocarbons, 0 to 6 % (m/m) tri+-aromatic hydrocarbons, 0 to 26 % (m/m) polycyclic aromatic hydrocarbons, and 4 to 65 % (m/m) total aromatic hydrocarbons.
1.3 Compounds containing sulfur, nitrogen, and oxygen are possible interferents. Mono-alkenes do not interfere, but conjugated di- and poly-alkenes, if present, are possible interferents.
1.4 By convention, this standard defines the aromatic hydrocarbon types on the basis of their elution characteristics from the specified liquid chromatography column relative to model aromatic compounds. Quantification is by external calibration using a single aromatic compound, which may or may not be representative of the aromatics in the sample, for each aromatic hydrocarbon type. Alternative techniques and methods may classify and quantify individual aromatic hydrocarbon types differently.
1.5 Fatty Acid Methyl Esters (FAME), if present, interfere with tri+-aromatic hydrocarbons. If this method is used for diesel containing FAME, the amount of tri+-aromatics will be over estimated.
1.6 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 and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D1319 Test Method for Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption
D2425 Test Method for Hydrocarbon Types in Middle Distillates by Mass Spectrometry
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D5186 Test Method for Determination of the Aromatic Content and Polynuclear Aromatic Content of Diesel Fuels and Aviation Turbine Fuels By Supercritical Fluid Chromatography
D6379 Test Method for Determination of Aromatic Hydrocarbon Types in Aviation Fuels and Petroleum Distillates - High Performance Liquid Chromatography Method with Refractive Index Detection
2.2 Energy Institute Standard:
IP 548 Test Method for Determination of Aromatic Hydrocarbon Types in Middle Distillates - High Performance Liquid Chromatography Method with Refractive Index Detection
3. Terminology
3.1 Definitions ofTerms Specific to This Standard:
3.1.1 di-aromatic hydrocarbons (DAHs), n - in this test method, compounds that have a longer retention time on the specified polar column than the majority of mono-aromatic hydrocarbons, but a shorter retention time than the majority of tri+-aromatic hydrocarbons.
3.1.2 mono-aromatic hydrocarbons (MAHs), n - in this test method, compounds that have a longer retention time on the specified polar column than the majority of non-aromatic hydrocarbons but a shorter retention time than the majority of DAHs.
3.1.3 non-aromatic hydrocarbons, n - in this test method, compounds that have a shorter retention time on the specified polar column than the majority of mono-aromatic hydrocarbons.
3.1.4 polycyclic aromatic hydrocarbons (POLY-AHs), n - in this test method, sum of the di-aromatic hydrocarbons and tri+-aromatic hydrocarbons.
3.1.5 total aromatic hydrocarbons, n - in this test method, sum of the MAHs, DAHs, and T+AHs.
3.1.6 tri+-aromatic hydrobons (T+AHs), n - in this test method, compounds that have a longer retention time on the specified polar column than the majority of DAHs.
3.1.6.1 Discussion - The elution characteristics of aromatic and non-aromatic compounds on the specified polar column have not been specifically determined for this test method. Published and unpublished data indicate the major constituents for each hydrocarbon type as follows: (1) non-aromatic hydrocarbons: acyclic and cyclic alkanes (paraffins and naphthenes), mono-alkenes (if present), (2) MAHs: benzenes, tetralins, indanes, thiophenes, and conjugated poly-alkenes, (3) DAHs: naphthalenes, biphenyls, indenes, fluorenes, acenaphthenes, and benzothiophenes and dibenzothiophenes, (4) T+AHs: phenanthrenes, pyrenes, fluoranthenes, chrysenes, triphenylenes, and benzanthracenes.
