ICP iron, PQ and ferrography answer different questions
Elemental concentration, bulk ferromagnetic response and particle morphology are complementary views of a wear-debris population—not interchangeable measures.
Reviewed Jul 2026 · Oil Testing Atlas editorial teamWear debris spans dissolved material, very fine particles and large fragments. No single common oil-analysis technique describes that entire size and morphology range.
ICP-OES: elemental concentration with size limits
ICP-OES measures element-specific emission from material that reaches and responds in the plasma. It is effective for dissolved and fine particulate elements, but response can fall as particle size and preparation challenges increase.
Elemental patterns can suggest component metallurgy or contamination, but the concentration does not directly identify particle shape or a unique wear mechanism.
PQ: bulk ferromagnetic response
The particle quantifier responds to ferromagnetic material in the sample, including debris larger than the practical response range of routine ICP preparation. It is an index rather than a mass concentration.
A rising PQ response with comparatively modest ICP iron can indicate a shift toward larger ferrous particles and justify microscopy or filter examination.
Ferrography: morphology and wear-mode evidence
Analytical ferrography separates particles for microscopic examination. Size, shape, colour, surface and concentration patterns can support hypotheses such as rubbing, cutting, fatigue or corrosion.
Interpretation is specialist and partly descriptive. It is strongest when the analyst has equipment metallurgy, operating context and companion measurements.
- Compare method-consistent trends
- Inspect filters when large debris is plausible
- Use morphology as evidence, not proof of a component failure
Key takeaways
- 01ICP emphasises dissolved and fine elemental material
- 02PQ responds to bulk ferromagnetic debris
- 03Ferrography adds morphology
- 04The combined pattern is more diagnostic than any single result