ASTM D6293 Standard Test Method for Oxygenates and Paraffin, Olefin, Naphthene, Aromatic (O-PONA) Hydrocarbon Types in Low-Olefin Spark Ignition Engine Fuels by Gas Chromatography
11. Procedure
11.1 Load the necessary system set-point conditions, which include initial component temperatures, times at which column and trap temperature are changed, the initial positions of switching valves, and times when valve switches occur (see Note 12).
NOTE 12 - Commercial systems will have all parameters predetermined and accessible through the software. Other constructed systems will require experimentation and optimization of parameters to achieve the required component separation and precision.
11.2 When all component temperatures have stabilized at the analysis conditions, inject a representative 0.1 to 0.3-µL aliquot of sample (or test mixture) and start the analysis.
NOTE 13 - A 0.1-µL volume was used by cooperators for the precision study.
11.2.1 Starting the analysis should begin the data acquisition and should begin the timing function that controls all of the various programmed temperature changes and valve switching.
11.2.2 Upon completion of its programmed cycle, the system should automatically stop, generate a chromatogram, and print a report of concentrations.
12. Calculation
12.1 Calculations produce results that are reported in mass % and liquid volume %. Examine the report carefully to ensure that all peaks have been properly identified and integrated.
12.1.1 Calculate the mass % of each identified hydrocarbon group of a particular carbon number and individual oxygenate using Eq 1.
where:
M = mass % of an identified hydrocarbon group of a particular carbon number or individual oxygenate,
A = integrated area of the hydrocarbon group of a particular carbon number or individual oxygenate,
F = relative response factor for the hydrocarbon group, RRf, calculated using Eq 2 or from Table 6. For oxygenates, use the response factors from Table 7, or factors determined on the specific system (see 12.1.1.2), and
100 = factor to normalize corrected area % to 100 %.
12.1.1.1 Calculate the flame ionization detector response factor relative to methane, which is considered to have a response factor of unity (1), for each hydrocarbon group type of a particular carbon number using Eq 2. Olefin response is calculated on a hydrogenated basis.
where:
RRf = relative response factor for a hydrocarbon type group of a particular carbon number,
Caw = atomic mass of carbon, 12.011,
Cn = number of carbon atoms in the hydrocarbon type group, of a particular carbon number,
Haw = atomic mass of hydrogen, 1.008,
Hn = number of hydrogen atoms in the hydrocarbon type group of a particular carbon number, and
0.7487 = factor to normalize the result to a methane response of unity, (1).
12.1.1.2 Oxygenate flame ionization detector response factors used in the precision study were determined experimentally and are listed in Table 7.
12.1.2 Calculate the liquid volume % of each identified hydrocarbon group and oxygenate using Eq 3.
where:
V = liquid volume % of an identified hydrocarbon group of a particular carbon number or individual oxygenate,
M = previously defined, Eq 1, and
D = average relative density, kg/L at 20°C, (see Note 14) for the hydrocarbon group of a particular carbon number or individual oxygenate. For hydrocarbons, use Table 8 and for oxygenates, use Table 9.
NOTE 14 - Relative density of 15.5°C can also be used but Tables 8 and 9 will not apply.