INDIVIDUAL COMPONENTS IN ENGINE FUELS BY HIGH RESOLUTION GAS CHROMATOGRAPHY: ASTM D6729
EXPLANATION
Knowledge of the specified individual component composition (speciation) of gasoline fuels and blending stocks is useful for refinery quality control and product specification. Compliance in these areas may be determined through the use of this test method. This test method covers the determination of individual hydrocarbon components of spark-ignition engine fuels and their mixtures containing oxygenate blends (MTBE, ETBE, ethanol, etc.) with boiling ranges up to 225° C. Other light liquid hydrocarbon mixtures typically encountered in petroleum refining operations, such as blending stocks (napthas, reformats, alkylates, etc.) may also be analyzed. Individual component concentrations and precisions are determined in the range 0.01 to approximately 30 mass %. The test method also determines methanol, ethanol, t-butanol, MTBE, ETBE, TAME in engine fuels in the concentration range of 1 to 30 mass %.
TEST SUMMARY
Representative samples of the petroleum liquid are introduced into a gas chromatograph equipped with an open tubular (capillary) column coated with the specified stationary phase. Helium carrier gas transports the vaporized sample through the column, in which it is partitioned into individual components which are detected with a flame ionization detector as they elute from the end of the column. The detector signal is recorded digitally with an integrator or integrating computer. Each eluting component is identified by comparing its retention time to that established by analyzing reference standards or samples under identical conditions. The concentration of each component in mass % is determined by normalization of the peak areas after correction of selected components with detector response factors. The unknown components are reported individually and as a summary total.
TEST PRECISION
The repeatability and reproducibility estimates of individual components determination by this method are given in a format somewhat different than usually found in ASTM methods. See Annex A1.2 of Test Method ASTM D6729 for this information.
The bias of this test method cannot be determined since an appropriate standard reference material for such analysis is not available.
