ASTM D6728 Standard Test Method for Determination of Contaminants in Gas Turbine and Diesel Engine Fuel by Rotating Disc Electrode Atomic Emission Spectrometry
13. Procedure
13.1 Analysis of Fuel Samples - Analyze the test specimen in the same calibration curve program and manner as the standardization standards. A new disc electrode and re-pointed rod electrode must be used for each analysis. A laboratory grade paper towel or installation tool shall be used to install the disc electrode in order to protect it from contamination due to handling. Cleaning procedures recommended by the manufacturer shall be followed to avoid cross contamination or buildup of spilled sample.
13.2 Number of Analysis per Specimen - Fuel samples shall be analyzed three times by repeating the procedure in 13.1. The 20 % rule is used to reject one of the three analyses if it differs more than 20 % from the average of the others. At concentrations below 1 mg/kg, samples that differ more than 0.3 mg/kg can be rejected. Repeat the procedures in 13.1 until three similar analyses are obtained.
13.3 Analysis of Flammable Samples - A non-plastic specimen holder cover shall be used on the specimen holder when fuel samples that might catch on fire during the analysis are analyzed. The cover retards flaming that may attenuate the analytical signal. Most covers will fit on reusable or disposable specimen holders.
13.4 Quality Control with a Check Sample - Analyze a check sample at least every hour during continuous operation or every 25 samples during intermittent operation to confirm the performance of the instrument.
13.4.1 When Quality Control (QC)/Quality Assurance (QA) protocols are already established, the check sample can be used to confirm the reliability of the test result.
13.4.2 When there is no QC/QA protocol established, Appendix X1 can be used as the QC/QA system.
