ASTM D6667 Total Volatile Sulfur in Gaseous Hydrocarbons/Liquefied Petroleum Gases
ASTM D6667 Standard Test Method for Determination of Total Volatile Sulfur in Gaseous Hydrocarbons and Liquefied Petroleum Gases by Ultraviolet Fluorescence
13. Quality Control
13.1 Confirm the performance of the instrument or the test procedure by analyzing a quality control (QC) sample (see 6.5) after each calibration and at least each day of use thereafter (see 11.5).
13.1.1 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.

13.1.2 When there is no QC/QA protocol established in the testing facility, Appendix X1 can be used as the QC/QA system.

14. Precision and Bias
14.1 The following precision and bias data was derived from an inter-laboratory study that included samples in n-butane, isobutane, and propane/propylene mix.

14.2 Repeatability - The difference between two test 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 in only 1 case in 20, where X = the average of the two test results.
r = 0.1152(X)

14.3 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 in only 1 case in 20, where X = the average of the two test results,
R = 0.3130(X)

14.4 Bias - Bias for this test method was studied during the inter-laboratory study by analysis of certified-gravimetrically prepared calibration standards and sample materials and published in 2000 as a research report. This report indicated that the results obtained were within the repeatability of the test method.

14.5 Examples of the above precision estimates for selected absolute values of X are set out in Table 4.

15. Keywords
15.1 analysis; butane; fluorescence; gases; hydrocarbon; isobutane; LP; LPG; liquefied; petroleum; propane; sulfur; ultraviolet