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)
X1. HELPFUL HINTS FOR THE OPERATION OF THE TEST METHOD D5185 TEST
X1.1 It is extremely important to homogenize the used oil in the sample container to obtain a representative specimen. Otherwise, it can lead to erroneous results.
X1.1.1 Ultrasonic homogenization is preferred, but vortex homogenization can be used as an alternative.

X1.2 Check the temperature and humidity controls of the laboratory containing the ICPAES instruments, and verify adequacy for performing accurate and precise analyses. Ensure that stable environmental conditions exist throughout the period of use.

X1.3 Check the accuracy of elemental concentrations of commercially obtained calibration standards before use, either by comparing against suitable primary standards or by an independent analytical method.

X1.4 Verify the absence of analytes in all solvents and reagents used by performing a wavelength scan. The net intensity should be zero.

X1.5 Establish the preparation frequency of calibration standards by experiment. Prepare fresh working and check standards before each set of measurements, or daily, as appropriate.

X1.6 Check the linearity of the calibration curve of each analyte every three months or more frequently.

X1.7 Inspect torches before use for cracks, and discard or repair as appropriate.

X1.8 Use clean torches that are free of carbon buildup.

X1.9 Replace or clean the load coil if oxidation is observed.

X1.10 Allow the instrument to warm up for at least 30 min, or longer, as suggested by the manufacturer.

X1.11 Visually inspect the peristaltic pump tubing daily for cracks, and replace it if it is defective. Verify the uptake rates daily.

X1.12 Run the blank and appropriate check standard after every fifth sample or if at least 30 min have elapsed from the time of the last analysis. Recalibrate if the net intensity of the standard changes by more than 5% relative to the previous check.

X1.13 Allow sufficient rinse time (not less than 60 s) between measurements to avoid memory effects. Memory effects are present if a steady instead of an abrupt decrease in signal is observed from taking multiple measurements.

X1.14 Use the peak and background wavelengths suggested in the method, if possible. When there is a choice, such as with sequential instruments, choose the wavelengths that will yield signals of 100 to 1000 times the detection limit. Also, ensure that the chosen wavelengths will not be interfered with from unexpected elements.

X1.15 Check for all spectral interferences expected from the elements present in the sample. Follow the manufacturer's operating guide to develop and apply correction factors to compensate for the interferences. Avoid spectral interferences where possible by judicious choice of wavelength or by comparing the results of two different wavelengths for the same element. See Section 6 for guidance.

X1.16 If sulfur is to be determined, do not use commercially available standards that contain sulfonates. Prepare separate standards with known concentration of sulfur.

X1.17 When preparing multi-element standards, ensure that elements will not react with one another resulting in insoluble compounds.

X1.18 When analyzing used oils, use a high-solids Babing-ton type nebulizer to avoid plugging problems.

X1.19 Dilute the sample and standards as much as possible to minimize nebulizer transport effects caused by high viscosity oils or viscosity improvers and additives in the oil, and to reduce potential spectral interferences. Both standard and sample solutions should not contain more than 10 mass % oil.

X1.20 Ensure that the standard solutions contain the same mass % oil as sample solutions. Maintain the correct amount of oil by adding analyte-free base oil. Maintain consistent oil to solvent ratio when diluting.

X1.21 The internal standard procedure described in this test method must be used to eliminate nebulizer transport effects. Add the same exact concentration of internal standard element to all samples and standard solutions.

X1.22 Check for carbon buildup on the torch while nebulizing the working standard. Make the necessary adjustments to eliminate buildup. These adjustments may consist of the following:
X1.22.1 Reducing the pump rate.
X1.22.2 Increasing the auxiliary gas flow.
X1.22.3 Using a chilled spray chamber.
X1.22.4 Diluting the sample.
X1.22.5 Making other adjustments described in the instrument manual.

X1.23 Differences in the viscosities of the test specimen solutions and standard solutions can cause differences in the uptake rates adversely affecting the accuracy of the analysis. Use a base oil that is free of analytes and has a viscosity at room temperature as close as possible to that of the sample to be analyzed. These effects can be minimized by using a peristaltic pump or an internal standard. Use of a peristaltic pump is strongly recommended to provide a constant flow of the solution. Although this test method allows the use of an internal standard as optional, it is strongly recommended that this option be used. The companion Test Method D4951 makes the use of internal standard mandatory.

X1.24 Presence of particulates in the samples can plug the nebulizer causing low results. Use of a Babington type high solids nebulizer helps to minimize this effect.

SUMMARY OF CHANGES
Subcommittee D02.03 has identified the location of selected changes to this standard since the last issue (D5185–02) that may impact the use of this standard.
(1) Added Appendix X1 to give information on helpful hints for proper operation of this test method.

(2) Corrected typographical errors in the Nickel and Zinc wavelengths in Table 1.