ASTM D2622 standard test method for sulfur in petroleum products by wavelength dispersive X-ray fluorescence spectrometry
12. Reporting
12.1 For samples analyzed without dilution, report the result calculated in 11.3. For samples that have been diluted, report the result calculated in 11.4. Report the result as the total sulfur content, mass %, to three significant figures for concentrations greater than 0.1000 mass %. Below 0.1000 mass % (1000 mg/kg) report results in mg/kg to three significant figures between 1000 and 10 mg/kg, and to two significant figures below 10 mg/kg. For guidance in properly rounding significant figures, refer to the rounding method in Practice E 29. State that the results were obtained according to Test Method D2622.
12.1.1 For samples containing less than 100 mg/kg total sulfur, average the duplicate determinations and report that value as in 12.1.
12.2 The carbon/hydrogen (C/H) ratio correction formula, which is applicable when the base material used for the calibration standards is white oil and is derived from the best straight line shown in Fig. 1, is shown in Eq 11:
where:
SC/H = sulfur concentration corrected for C/H ratio matrix differences,
(C/H)whiteoil = mass ratio of carbon to hydrogen for white oil, 5.7 from Fig. 1,
(C/H) = mass ratio of carbon to hydrogen for the sample, and
Swhiteoil = sulfur concentration as derived from the calibration graph.
12.2.1 The value for C/H mass ratio is input for each unknown sample. The Swhiteoil will be corrected for the different C/H ratios. Accordingly, if standards are prepared with a different solvent, the C/H ratio for that solvent should be used in place of (C/H)whiteoil. Any difference between the C/H ratio between standards and samples will contribute to error in the measured result (see Table 6 for examples). It is the analyst's discretion as to when this error is large enough to be corrected by Eq 11.