ASTM D7171 Standard Test Method for Hydrogen Content of Middle Distillate Petroleum Products by Low-Resolution Pulsed Nuclear Magnetic Resonance Spectroscopy
14. Report
14.1 Report the mass % hydrogen content of the middle distillate test specimen to the nearest 0.01 mass % hydrogen.
15. Quality Control (QC)
15.1 As per the frequency indicated in 12.4, confirm the accuracy of the instrument by analyzing a check standard (see 3.1.4).
15.1.1 Determined values for the check standards shall be within 1.5 % relative of the known values before proceeding with sample analyses. Investigate and take appropriate corrective actions when results determined for the check standard fall outside the allowed range (see 12.5).
15.2 Confirm the performance of the instrument or the test procedure by analyzing a QC sample (see 7.3).
15.2.1 When QC/Quality Assurance (QA) protocols are already established in the testing facility, these may be used when they confirm the reliability of the test result.
15.2.2 When there is no QC/QA protocol established in the testing facility, Appendix X1 can be used as the QC/QA system.
16. Precision and Bias
16.1 Precision - The precision of this test method was determined at two temperatures, 35 °C and 40 °C, by the statistical examination of two interlaboratory studies, involving samples with nominal concentrations between 10.5 and 15.5 mass % hydrogen. The first interlaboratory study at 35 °C involved 9 laboratories and 12 middle distillate petroleum products analyzed in duplicate. The second interlaboratory study at 40 °C involved 10 laboratories and 12 middle distillate petroleum products run in duplicate. The precision determined is as follows, with calculated values for representative concentrations provided in Table 2.
16.1.1 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:
at 35 °C: r = 0.009352 (X + 1.7000)
at 40 °C: r = 0.006409 (X + 5.0000)
where:
X = mass % hydrogen content.
16.1.2 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, exceed the following values only in one case in twenty:
at 35 °C: R = 0.01769 (X + 1.7000)
at 40 °C: R = 0.01580 (X + 5.0000)
where:
X = mass % hydrogen content.
16.2 Bias - Since there are no accepted reference materials for determining bias for this test method, no statement on bias is being made.
17. Keywords
17.1 distillates; fuels; hydrogen content; middle distillate; nuclear magnetic resonance spectrometer; petroleum products
