Standard Test Method for Determination of Additive Elements, Wear Metals, and Contaminants in Used Lubricating Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)

This test method covers the rapid determination of 22 elements in used lubricating oils and in base oils, and it provides rapid screening of used oils for indications of wear. Test times approximate a few minutes per test specimen, and detectability for most elements is in the low mg/kg range. In addition, this test method covers a wide variety of metals in virgin and re-refined base oils. Twenty-two elements can be determined rapidly, with test times approximating several minutes per test specimen.

When the predominant source of additive elements in used lubricating oils is the additive package, significant differences between the concentrations of the additive elements and their respective specifications can indicate that the incorrect oil is being used. The concentrations of wear metals can be indicative of abnormal wear if there are baseline concentration data for comparison. A marked increase in boron, sodium, or potassium levels can be indicative of contamination as a result of coolant leakage in the equipment. This test method can be used to monitor equipment condition and define when corrective actions are needed.

The concentrations of metals in re-refined base oils can be indicative of the efficiency of the re-refining process. This test method can be used to determine if the base oil meets specifications with respect to metal content.

1.1 This test method covers the determination of additive elements, wear metals, and contaminants in used lubricating oils by inductively coupled plasma atomic emission spectrometry (ICP-AES). The specific elements are listed in Table 1.

1.2 This test method covers the determination of selected elements, listed in Table 1, in re-refined and virgin base oils.

1.3 For analysis of any element using wavelengths below 190 nm, a vacuum or inert-gas optical path is required. The determination of sodium and potassium is not possible on some instruments having a limited spectral range.

1.4 This test method uses oil-soluble metals for calibration and does not purport to quantitatively determine insoluble particulates. Analytical results are particle size dependent, and low results are obtained for particles larger than a few micrometers.

1.5 Elements present at concentrations above the upper limit of the calibration curves can be determined with additional, appropriate dilutions and with no degradation of precision.

1.6 For elements other than calcium, sulfur, and zinc, the low limits listed in Table 2 and Table 3 were estimated to be ten times the repeatability standard deviation. For calcium, sulfur, and zinc, the low limits represent the lowest concentrations tested in the interlaboratory study.

               TABLE 1 Elements Determined and Suggested WavelengthsA

  Element Range, mg/kg Repeatability, μg/gA
  Aluminum 640 0.71 X0.41
  Barium 0.54 0.24 X0.66
  Boron 430 0.26 X
  Calcium 409000 0.0020 X1.4
  Chromium 140 0.17 X0.75
  Copper 2160 0.12 X0.91
  Iron 2140 0.13 X0.80
  Lead 10160 1.6 X0.32
  Magnesium 51700 0.16 X0.86
  Manganese 5700 0.010 X1.3
  Molybdenum 5200 0.29 X0.70
  Nickel 540 0.52 X0.49
  Phosphorus 101000 1.3 X0.58
  Potassium 401200 3.8 X0.33
  Silicon 850 1.3 X0.26
  Silver 0.550 0.15 X0.83
  Sodium 770 0.49 X0.66
  Sulfur 9006000 0.49 X0.81
  Tin 1040 2.4 X0.17
  Titanium 540 0.54 X0.37
  Vanadium 150 0.061 X
  Zinc 601600 0.15 X0.88

A These wavelengths are only suggested and do not represent all possible choices.



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