Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D5185-18 – Standard Test Method Technical Guide
📋 Overview and Scope
ASTM D5185-18, issued under the fixed designation D5185, is a standard test method for the multielement determination of used and unused lubricating oils and base oils using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Originally approved in 1991, this revision supports diagnostic methods for engine and machinery condition monitoring, addressing significant maintenance costs. The method covers additive elements, wear metals, and contaminants as listed in Table 1, including re-refined and virgin base oils. It conforms to international standardization principles and is approved for use by U.S. Department of Defense agencies.
⚙️ Test Procedure and Calibration
The test method employs oil-soluble metals for calibration and does not quantitatively determine insoluble particulates; results are particle size dependent, with low accuracy for particles larger than a few micrometers. For wavelengths below 190 nm, a vacuum or inert-gas optical path is required, and sodium and potassium determination may be limited on instruments with restricted spectral range. Elements above the calibration curve can be analyzed with additional dilutions without precision degradation. The procedure includes specific safety warnings for handling and operation.
| 🟦 Element | 📏 Low Limit Basis | ⚡ Remarks |
|---|---|---|
| Calcium | Lowest concentration from ILS | Specific limit in Table 2/3 |
| Sulfur | Lowest concentration from ILS | Specific limit in Table 2/3 |
| Zinc | Lowest concentration from ILS | Specific limit in Table 2/3 |
| Other Elements | 10× repeatability standard deviation | Estimated low limits |
📊 Precision and Limits
The precision statement was derived from analyzing a variety of used oils. For elements other than calcium, sulfur, and zinc, low limits are estimated as ten times the repeatability standard deviation. For calcium, sulfur, and zinc, low limits represent the lowest concentrations tested in the interlaboratory study. Values are expressed in SI units, and the method can be applied to unused oils for more complete elemental composition data compared to Test Methods D4628, D4927, or D4951.
⚠️ Note on Particle Size: This test method is not intended for quantitative determination of insoluble particulates. Samples with particles larger than a few micrometers may yield low results.
💡 Dilution for High Concentrations: Elements above the upper calibration limit can be determined with appropriate dilutions without precision loss, ensuring flexibility for diverse sample matrices.
❓ Frequently Asked Questions
🔍 What is the primary purpose of ASTM D5185-18?
The standard is used for multielement determination in lubricating oils to monitor additive elements, wear metals, and contaminants, aiding in equipment maintenance and condition diagnostics.
💡 Can this method analyze insoluble particles?
No, it is designed for oil-soluble metals, and results are particle size dependent, with low accuracy for particles larger than a few micrometers.
⚡ Are there limitations for sodium and potassium analysis?
Yes, on instruments with limited spectral range, sodium and potassium may not be determinable, especially for wavelengths below 190 nm requiring a vacuum or inert-gas path.
📌 How are high concentrations handled?
High concentrations above the calibration curve can be addressed through additional dilutions without degradation of precision.