ASTM D5580 Standard Test Method for Determination of Benzene, Toluene, Ethylbenzene, p/m-Xylene, o-Xylene, C9 and Heavier Aromatics, and Total Aromatics in Finished Gasoline by Gas Chromatography
14. Calculation and Report
14.1 Mass Concentration of Aromatics - After identifying the peaks, measure the areas of benzene, toluene, and the internal standard from the first analysis and the internal standard, ethylbenzene, p/m-xylene, o-xylene, C9 and heavier aromatics from the second analysis. Using the slope and y-intercept of the least square fit calibrations in 11.4.2, calculate the mass of each aromatic component (Wi) in the gasoline samples using the response ratio (rspi) of the areas of the aromatic component to the internal standard as follows:
where:
Wi = mass of aromatic component i,
Ai = area of aromatic component i,
As = area of internal standard, and
Ws = mass of internal standard added.
14.1.1 To obtain mass percent (w i) results for each component:
where:
Wg = mass of gasoline sample.
14.1.2 Report the mass percent (wi) results of the following aromatics to the nearest 0.01 %; benzene, toluene, ethylbenzene, p/m-xylene, o-xylene, C9 and heavier aromatics.
14.1.3 To obtain the total mass percent aromatics, sum the mass percent (wi) results of all the individual aromatic components i.
14.2 Volumetric Concentration of Aromatic Components - If the volumetric concentration of each aromatic component i is desired, calculate the volumetric concentration in accordance with Eq 15:
where:
vi = volume percent of each aromatic component to be determined,
Df = relative density of the fuel under study as determined in accordance with Test Method D1298 or Test Method D4052, and
Di = relative density at 15.56°C (60°F) of the individual aromatics (Table 2).
14.2.1 Report the volume percent results (vi) of the following aromatic components to the nearest 0.01 %; benzene, toluene, ethylbenzene, p/m-xylene, o-xylene, and C9 and heavier aromatics.
14.2.2 To obtain total volume percent aromatics, sum the volume percent (vi) results of all the individual aromatic components i.
15. Precision and Bias
15.1 Precision - The precision of this test method as determined by the statistical examination of the interlaboratory test reports is as follows:
15.1.1 Repeatability - The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test materials would, in the long run, in the normal and correct operation of the test method exceed the following values in only one case in twenty. See Table 4.
15.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical material, would in the long run, exceed the following values in one case in twenty. See Table 5.
15.1.3 Bias - Since there is no accepted reference material suitable for determining bias for the procedure in this test method, no statement of bias is being made.
16. Keywords
16.1 aromatics; benzene; ethylbenzene; gas chromatography; gasoline; toluene; xylenes