ASTM D5443 Standard Test Method for Paraffin, Naphthene, and Aromatic Hydrocarbon Type Analysis in Petroleum Distillates Through 200°C by Multi-Dimensional Gas Chromatography
10. Procedure
10.1 Refer to Practice D4057 for instructions on manual sampling from bulk storage into open containers. Stopper the container immediately after drawing sample.
10.2 Place the instrument in the initial configuration as illustrated in Fig. 3.
10.3 Adjust the operating conditions to those values that were experimentally determined in 9.3 to give the desired separations. This may be done programmatically for automated instruments.
10.4 Inject approximately 0.2 µL of sample and begin data acquisition of the detector signal. A chromatogram is required for hydrocarbon type group identification. Integrated peak areas are required for calculations of mass percent.
10.5 Stop the data acquisition after the final cut has been eluted.
11. Calculation
11.1 Identify each hydrocarbon type group by visually matching it with its counterpart in the hydrocarbon test mixture, Fig. 14 and Table 7. The performance characteristics of the molecular sieve column and the sample composition may result in separation of the normal and iso-paraffins by carbon number. These groups can be combined in the calculations and reported as paraffins, by carbon number. Each of the aromatic components may elute in several of the aromatic fractions. Identify and total each of these components within the appropriate hydrocarbon type group. Peak characteristics will vary and depend on component concentrations in the sample. A qualitative reformer feed may also be used to aid in identification, as in Fig. 15.
11.2 If a computing integrator is used for automatic peak identification, examine the report carefully to ensure that all peaks are properly identified and integrated.
11.3 Response Factors - All groups are reported in mass percent, normalized to 100 %. The following formula is used to calculate the flame ionization detector response factors, as listed in Table 8:
where:
Fi = relative response factor for a hydrocarbon type group of a particular carbon number,
Caw = atomic weight of carbon, 12.011,
Cn= number of carbon atoms in the group,
Haw = atomic weight of hydrogen, 1.008,
Hn= number of hydrogen atoms in the group, and
0.7487 = corrects the response of methane to unity.
Methane will be considered to have a unity (1) response factor.
11.3.1 Use an average response factor of 0.88 for the first three fractions boiling above 200°C. Use a response factor of 0.85 for the last fraction boiling above 200°C. Use an average response factor of 0.835 for C9 and above aromatics.
11.4 Multiply the area associated with each of the identified groups by the appropriate response factor to produce a corrected area for each of the groups:
Aic = Ai x Fi
where:
Aic = corrected area of an identified group, and
Ai = raw area of identified group.
11.5 Add all of the individual, corrected areas from 11.4.
T = ∑Aic
where:
T = total of corrected areas.
11.6 Divide each of the identified groups by the total corrected area determined in 11.5 to produce the normalized mass percent for each group:
where:
Mi = normalized mass % of an identified group.