ASTM D3710 for Boiling Range Distribution of Gasoline and Gasoline Fractions
ASTM D3710 Standard Test Method for Boiling Range Distribution of Gasoline and Gasoline Fractions by Gas Chromatography
4. Summary of Test Method
4.1 The sample is introduced into a gas chromatographic column which separates hydrocarbons in boiling point order. Conditions are selected so as to measure isopentane and lighter saturates discretely. Normal pentane and heavier compounds are not completely resolved but are measured as pseudo components of narrow boiling range. The column temperature is raised at a reproducible rate and the area under the chromatogram is recorded throughout the run. Boiling temperatures are assigned to the time axis from a calibration curve, obtained under the same conditions by running a known mixture of hydrocarbons covering the boiling range expected in the sample. From these data the boiling range distribution of the sample is obtained.
5. Significance and Use
5.1 The determination of the boiling range distribution of gasoline by GC distillation provides an insight into the composition of the components from which the gasoline has been blended. This insight also provides essential data necessary to calculate the vapor pressure of gasoline, which has been traditionally determined by Test Method D323. In addition, the Test Method D86 distillation curve can be predicted using GCD data. See Annex A1.
5.2 The GCD method facilitates online controls at the refinery, and its results offer improved means of describing several car performance parameters. These parameters include: (1) car-starting index, (2) vapor-lock index or vapor-liquid ratio, and (3) warm-up index. The car-starting and vapor-lock indexes have been found to be mostly affected by the front end of the Test Method D86 distillation curve (up to about 200°F (93°C)). The warm-up index is affected by the middle and to a lesser extent by the back end of the Test Method D86 curve, that is, the temperatures corresponding to the 50 to 90 % off range. Since the boiling range distribution provides fundamental information on composition, an improved expression for the above performance parameters may be worked out, even when the boiling range distribution curve is not smooth. Currently, car performance cannot be assessed accurately under such conditions.
