ASTM D7751 Standard Test Method for Determination of Additive Elements in Lubricating Oils by EDXRF Analysis
13. Procedure
13.1 When using drift correction monitors, prior to analyzing samples on a given day, analyze the drift correction monitor(s) and determine the counting rate, using the same material as used at the time of calibration.
13.2 Analyze QC samples prior to analyzing a batch of samples, as described in 12.5.
13.3 When analyzing additive packages or lubricating oil with concentration outside the ranges listed in Table 1, dilute the sample with a contamination free diluent (base oil) prior to analysis. The dilution factor has to be calculated from the expected concentrations to bring the concentrations for all elements into the ranges listed in Table 1.
13.4 Place the sample in an appropriate cell using techniques consistent with good practice for the particular instrument being used. When filling the sample cup, follow procedure described in 10.2.
13.5 Place the sample in the instrument and perform measurement according to instrument manufacturer's instructions.
13.6 Determine the intensities for all elements of interest.
NOTE 3 - It is recommended that each sample is prepared and analyzed immediately. Also, it is recommended that care be taken not to leave the test sample in the instrument after the measurement process has finished.
14. Calculation or Interpretation of Results
14.1 When using the drift correction monitor, calculate correction factors for changes in instrument sensitivity. Use these correction factors to calculate corrected intensities for the elements of interest.
14.2 Calculate the concentrations of the elements of interest by inserting the intensities in the calibration created in Section 12. In many cases the instrument vendor will provide software with the required calculations.
14.3 When analyzing a sample which has been diluted prior to analysis, correct the results with the dilution factor used for the dilution of the sample.
