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)
7. Apparatus
7.1 Balance, top loading, with automatic tare, capable of weighing to 0.001 g, capacity of 150 g.
7.2 Inductively-Coupled Plasma Atomic Emission
Spectrometer - Either a sequential or simultaneous spectrometer is suitable, if equipped with a quartz ICP torch and RF generator to form and sustain the plasma. Suggested wavelengths for the determination of the elements in used oils are given in Table 1. For the analysis of sulfur, the spectrometer must be capable of operating in the wavelength region of 180 nm.
7.3 Nebulizer - A Babington-type high-solids nebulizer is strongly recommended. This type of nebulizer reduces the possibility of clogging and minimizes aerosol particle effects.
7.4 Peristaltic Pump, (Recommended) - A peristaltic pump is strongly recommended to provide a constant flow of solution. The pumping speed must be in the range 0.5 to 3 mL/min. The pump tubing must be able to withstand at least 6 h exposure to the dilution solvent. Viton tubing is typically used with hydrocarbon solvents, and poly-vinyl chloride tubing is typically used with methyl isobutyl ketone.
7.5 Solvent Dispenser, (Optional) - A solvent dispenser calibrated to deliver the required weight of dilution solvent for a ten-fold dilution of test specimen is very useful.
7.6 Specimen Solution Containers, of appropriate size, glass or plastic vials or bottles, with screw caps.
7.7 Ultrasonic Homogenizer, (Recommended) - A bath-type or probe-type ultrasonic homogenizer to homogenize the sample.
7.8 Vortexer, (Optional) - Vortexing the sample is an alternative to ultrasonic homogenization.
8. Reagents and Materials
8.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
8.2 Base Oil - U.S.P. white oil, or a lubricating base oil that is free of analytes, and having a viscosity at room temperature as close as possible to that of the samples to be analyzed. (Warning - Lubricating base oils contain sulfur. For sulfur determinations, white oil is recommended for the preparation of standards.
8.3 Internal Standard - Oil-soluble cadmium, cobalt, or yttrium (or any other suitable metal) are required when the internal standardization option is selected.
8.4 Organometallic Standards - Multi-element standards, containing 0.0500 mass % of each element, can be prepared from the individual concentrates. Refer to Practice D4307 for a procedure for preparation of multicomponent liquid blends. When preparing multi-element standards, be certain that proper mixing is achieved. An ultrasonic bath is recommended. Standard multi-element concentrates, containing 0.0500 mass % of each element, are also satisfactory. (Warning - Some commercially available organometallic standards are prepared from metal sulfonates and therefore contain sulfur. For sulfur determinations, a separate sulfur standard would be required.)
NOTE 1 - Secondary standards such as those prepared from petroleum additives, for example, can be used in place of those described. If the use of such secondary standards does not affect the analytical results by more than the repeatability of this test method.
8.5 Sulfur Standard - To use a metal sulfonate as a sulfur standard, analyze the sulfonate by Test Method D1552. Alternatively, prepare a sulfur standard by diluting NIST SRM 1622c in white oil.
8.6 Dilution Solvent - A solvent that is free of analytes and is capable of completely dissolving all standards and samples. Mixed xylenes, kerosine, and ortho-xylene were successfully used as dilution solvents in the interlaboratory study on precision.
