ASTM D6728 Standard Test Method for Determination of Contaminants in Gas Turbine and Diesel Engine Fuel by Rotating Disc Electrode Atomic Emission Spectrometry
14. Report
14.1 Fuel Samples - Fuel samples shall be reported as an average of three separate analyses made on the same sample. Data shall be in mg/kg and to one decimal place for concentrations below 99.9 mg/kg and in whole numbers for concentrations greater than 100 mg/kg.
15. Precision and Bias
15.1 Precision - The precision of this test method was determined by statistical analysis of interlaboratory results obtained by following this test method. A total of seven laboratories participated in the Interlaboratory Study (ILS) and sent in data on twelve fuel samples and standards analyzed in duplicate in accordance with the procedure described in 13.1-13.4. The samples in the ILS consisted of distillate fuel oils, crude oil, residual fuels and calibration standards. Data is available in a research report.
15.1.1 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 values in Tables 2-5 only in one case in twenty. Tables 2 and 3 are for light fuels (ASTM No. 0-GT, No. 1-GT, No. 2-GT, Grade 1-D, Grade 2-D, and Grade 4-D fuel oils) and Tables 4 and 5 for heavy fuels (No. 3-GT and No. 4-GT fuel oils).
15.1.2 Reproducibility - The difference between two single and independent results, obtained by different operators working in different laboratories on identical test materials, would in the long run, in the normal and correct operation of the test method, exceed the values in Tables 6-9 only in one case in twenty. Tables 6 and 7 are for light fuels (ASTM No. 0-GT, No. 1-GT, No. 2-GT, Grade 1-D, Grade 2-D, and Grade 4-D fuel oils) and Tables 8 and 9 for heavy fuels (No. 3-GT and No. 4-GT fuel oils).
15.2 Bias - Bias was evaluated by analyzing two samples prepared from calibration standards at the 5 mg/kg and 10 mg/kg concentrations for light fuels and 10 mg/kg and 30 mg/kg concentrations for heavy fuels. The t-test concluded for light fuels that the bias was insignificant with the exception of calcium, copper, sodium, and zinc at 5 mg/kg concentration, and for heavy fuels, aluminum and nickel at 30 mg/kg.
16. Keywords
16.1 ash-forming materials; contaminant; disc electrode; emission spectrometry; fuel analysis; RDE; rod electrode; rotating disc electrode spectrometer; trace metals
