14. Procedure
14.1 Analysis - Analyze the test specimen solutions in the same manner as the calibration standards (that is, same integration time, background correction points, plasma conditions, etc.). Between test specimens, nebulize dilution solvent. In many instruments switching valves are in use and will reduce the needed rinse time. A rinsing time of 60 s for peristaltic pump samples may be necessary but different rinse times are possible as long as baseline intensities are achieved. Calculate elemental concentrations by multiplying the determined concentration in the diluted test specimen solution by the dilution factor. Calculation of concentrations can be performed manually or by computer when such a feature is available.
14.2 When the concentration of any analyte exceeds the linear range of the calibration curve, prepare another test specimen by mixing the sample with base oil or white oil before adding diluent. Then analyze.
14.3 Quality Control with Check Standard - Analyze the check standard after every fifth sample, and if any result is not within 5 % of the expected concentration, recalibrate the instrument and reanalyze the test specimens solutions back to the previous acceptable check standard analysis.
NOTE 6 - To verify the accuracy and precision of the instrument calibration, certified standards such as NIST SRM 2721, 2722, or RM 8505 should be regularly analyzed.
14.4 Analysis with Internal Standardization - Analyze the test specimen solutions and calculate an intensity ratio for each of the elements found in the test specimen solutions using Eq 1 given in 11.3. From these intensity ratios, concentrations of the elements can be calculated.
15. Calculations
15.1 Calculate the concentrations, based on sample, using Eq 2. Generally, the ICP instrument software performs this calculation automatically.
C = analyte concentration in the sample mass %,
S = analyte concentration in the test specimen, mass %,
W1 = sample mass, g,
W2 = diluent mass, g, and
W3 = base oil mass (if any), g.
16. Quality Control
16.1 Confirm the performance of the instrument and the test procedure by analyzing a control (QC) sample. See Guide D6792 for guidance.
16.1.1 When QA/QC protocols are already established in the testing facility, these may be used to confirm the reliability of the test result.
16.1.2 When there is no QA/QC protocol established in the testing facility, Appendix X1 can be used as the QA/QC protocol.
16.2 Users ofthis test method are advised that in contractual agreements, one or more ofthe contracting parties can and may make Appendix X1 a mandatory practice.