ASTM D5185 for additive elements, wear metals, contaminants and selected elements
ASTM D5185 Standard Test Method for Determination of Additive Elements, Wear Metals, and Contaminants in Used Lubricating Oils and Determination of Selected Elements in Base Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
13. Sample Handling
13.1 Homogenization - It is extremely important to homogenize the used oil in the sample container in order to obtain a representative test specimen.
13.2 Ultrasonic Homogenization - Place the used oil (in the sample container) into the ultrasonic bath. For very viscous oils, first heat the sample to 60°C. Leave the sample in the bath until immediately before dilution.
13.3 Vortex Homogenization - As an alternative to ultrasonic homogenization, vortex mix the used oil in the sample container, if possible. For viscous oils, first heat the sample to 60°C.
14. Preparation of Test Specimens and Standards
14.1 Blank - Prepare a blank by diluting the base oil or white oil ten-fold by mass with the dilution solvent.
14.2 Working Standard, 10 µg/mL - Weigh 2 g of the 0.0500 mass % multi-element standard into a 4-oz. glass bottle, add 8 g of base oil and dilute with 90 g of dilution solvent. Working standards containing higher or lower concentrations can be prepared depending on the concentrations of additive elements, wear metals, or contaminants in the used oils. In addition, solutions containing single elements can also be prepared. However, ensure that the ten-fold dilution is maintained for all solutions.
14.3 Check Standards - Prepare instrument check standards in the same manner as the working standards such that the concentrations of elements in the check standards are similar to the concentrations of elements in the specimens.
14.4 Test Specimen - Weigh a portion of the well-homogenized sample into a suitable container. Add dilution solvent until the test specimen concentration is 10 mass %.
14.5 Internal Standard - If an internal standard is being used, add internal standard solution to the working standard, check standard, and test specimen before diluting with the dilution solvent. Ensure that the standard or test specimen concentration is 10 mass %. Alternatively, the internal standard can be present in the dilution solvent.
15. Procedure and Calculation
15.1 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 for 60 s. 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.
15.2 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 3 - To verify the accuracy and precision of the instrument calibration, certified standards such as SRM 1085 should be regularly analyzed.
15.3 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 9 given in 11.3. From these intensity ratios, concentrations of the elements can be calculated.
