ASTM D6443 Copper, Phosphorus and Sulfur in Unused Lubricating Oils and Additives
ASTM D6443 Standard Test Method for Determination of Calcium, Chlorine, Copper, Magnesium, Phosphorus, Sulfur, and Zinc in Unused Lubricating Oils and Additives by Wavelength Dispersive X-ray Fluorescence Spectrometry (Mathematical Correction Procedure)
6. Apparatus
6.1 X-ray Spectrometer, equipped for detection of soft X-ray radiation in the range from 1 to 10 angstroms. For optimum sensitivity, the spectrometer is equipped with the following:
6.1.1 X-ray Tube Source, with chromium, rhodium, or scandium target. Scandium can be advantageous for sensitivity enhancement of the low atomic number analytes. Other targets may also be employed. Avoid spectral interferences from tube lines on the analyte lines.
6.1.2 Helium, purgeable optical path.
6.1.3 Interchangeable Analyzer Crystals, germanium, lithium fluoride (LiF200), graphite, pentaerythritol (PE), or a 50 angstrom diffraction structure, or a combination thereof. Other suitable crystals can be used.
6.1.4 Pulse-Height Analyzer.
6.1.5 Detector, gas flow proportional, or tandem gas flow proportional and scintillation counter.
NOTE 1 - A gas sealed proportional counter was used in the interlaboratory study on precision and was found to be satisfactory.
6.2 Mixing Device Such As a Shaker, Ultrasonic Bath, or Vortex Mixer, capable of handling from 30-mL to 1-L bottles.
6.3 X-ray Disposable Plastic Cells, with suitable film window. Suitable films can include polyester, polypropylene, or polyimide. A film thickness of 4 µm is preferred. Avoid using film that contains any of the analytes.
7. Reagents and Materials
7.1 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 can 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.
7.2 Helium, preferably ultrahigh purity (at least 99.95 %), for optical path of spectrometer.
7.3 P-10 Ionization Gas, 90 volume % argon and 10 volume % methane for the flow proportional counter.
NOTE 2 - P-10 gas was used in the interlaboratory study on precision. Other satisfactory gases or gas mixtures can be applicable.
7.4 Dilution Solvent, a hydrocarbon solvent, which does not contain a detectable amount of any analyte. U.S.P. white (mineral) oil has been found to be satisfactory.
7.5 Calibration Standard Materials:
7.5.1 Concentrated Solutions of Oil-soluble Compounds, each containing one of the following: calcium, copper, magnesium, phosphorus, or zinc.
7.5.1.1 Some commercially available oil-soluble standard materials are prepared from sulfonates and therefore contain sulfur. To use these materials for preparation of the calibration standard blends, it is necessary to know their sulfur concentrations. Test Method D1552, or other appropriate methods, can be used to determine sulfur content.
7.5.1.2 Secondary standards, such as those prepared from petroleum additives, for example, can also be used if their use does not affect the analytical results by more than the repeatability of this test method.
7.5.2 Di-n-butyl Sulfide, a high-purity standard with a certified analysis for total sulfur content.
NOTE 3 - Di-n-butyl sulfide is flammable and toxic.
7.5.3 Oil-soluble Chlorine-containing Compound, a high purity standard with a certified analysis for total chlorine content.
7.5.4 Stabilizers, Stabilizers can be used to ensure uniformity of the calibration standard blends. Use stabilizers that do not contain a detectable amount of any analyte.
8. Sampling and Sample Handling
8.1 Take samples in accordance with the instructions in Practice D4057 or D4177, when applicable.
8.2 Mix well samples and calibration standard blends before introduction into the X-ray instrument.
