ASTM D6376 Standard Test Method for Determination of Trace Metals in Petroleum Coke by Wavelength Dispersive X-ray Fluorescence Spectroscopy
12. Procedure
12.1 Place the analytical sample pellet into the sample holder and place both into the X-ray spectrometer. Avoid touching or otherwise contaminating the flat sample surface.

12.2 Evacuate the optical path.

12.3 Collect intensity data at the angles and under the conditions indicated in Table 2 or suitable substitutes.

12.4 Use pulse height discrimination on the gas-flow proportional detector.

12.5 Calculate results by operating the data collection and calculation software to produce analytical results by using the calibration equations developed in Section 11. Calculations are thus hidden within the computer program.

13. Precision and Bias
13.1 The precision of this test method, as obtained by statistical examination of interlaboratory test results, is as follows:
13.1.1 Repeatability - The difference between successive test results, obtained by the same operator with the same apparatus under constant operating conditions on identical test material, would in the long run, in the normal and correct operation of the test method, exceed the values in Table 3 only in one case in twenty.

13.1.2 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 values in Table 3 only in one case in twenty.

13.2 Bias - A result from this test method does not differ from the actual value by more than the reproducibility of the test method.

14. Keywords
14.1 alpha; aluminum; calcined petroleum coke; calcium; green petroleum coke; iron; manganese; nickel; petroleum coke; raw petroleum coke; silicon; sodium; spectrophotometry; sulfur; titanium; vanadium; X-ray fluorescence