ASTM D7039 Standard Test Method for Sulfur in Gasoline, Diesel Fuel, Jet Fuel, Kerosine, Biodiesel, Biodiesel Blends, and Gasoline-Ethanol Blends by Monochromatic Wavelength Dispersive X-ray Fluorescence Spectrometry
13. Reporting
13.1 Report sulfur concentration of the test sample calculated from Section 12 using units of mg/kg, rounded to the nearest 0.1 mg/kg for concentrations <100 mg/kg, and rounded to the nearest 1 mg/kg for concentrations ≥100 mg/kg. Indicate that the results were obtained according to Test Method D7039.
14. Quality Control
14.1 Confirm the satisfactory performance of the instrument and the test procedure by analyzing a quality control sample (see 7.5) at least once each day the analyzer is used.
14.2 When quality control/quality assurance (QC/QA) protocols are already established in the testing facility, they can be used, provided they include procedures to monitor the reliability of the test results.
14.3 When there is no QC/QA protocol established in the testing facility, the system described in Appendix X2 can be used.
15. Precision and Bias
15.1 Precision - The precision of this test method was determined by statistical analysis of results obtained in an interlaboratory study in accordance with Practice D6300. Precision was calculated by using data from nine analyzers at nine different laboratories. Each laboratory analyzed a sample set in blind duplicate. Precision was calculated by using data from 22 sulfur-containing materials, including five gasolines, seven diesel and biodiesel blends, three jet fuels, one kerosine, three biodiesels, and three gasoline-ethanol blends. The range of the measured average sulfur levels was 1.1 mg/kg to 2822 mg/kg. A pooled limit of quantitation (PLOQ) (calculated by procedures consistent with Practice D6259) of 3.2 mg/kg sulfur was determined.
15.1.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would in the long run, in the normal and correct operation of the test method, exceed the following values only in one case in twenty. Repeatability (r) may be calculated as shown in Eq 7 for all materials covering the full scope of this method. See Table 6 for calculated values.
Repeatability (r) = 0.4998·X(0.54)
where:
X = the average sulfur concentration of two results in mg/kg.
15.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following values only in one case in twenty. Reproducibility (R) may be calculated as shown in Eq 8 for all materials covering the full scope of this method. See Table 6 for calculated values.
Reproducibility (R) = 0.7384·X(0.54)
where:
X = the average sulfur concentration of two results in mg/kg.
15.2 Bias - No statistically significant bias was observed for this test method in gasoline and diesel fuel at the concentrations specified in Table 7 using NIST Standard Reference Materials (SRMs) SRM 2298, SRM 2723a, and SRM 2724b. Other biases were not determined; however, bias due to differences in the hydrogen, carbon, and oxygen content of the test samples and calibration standards may be corrected by following Section 5.
16. Keywords
16.1 analysis; biodiesel; diesel; fuel; gasoline; jet fuel; kerosine; monochromatic X ray; MWDXRF; spectrometry; sulfur; wavelength dispersive X-ray fluorescence; WDXRF; X-ray
