ASTM D7843 is the standard test method for the measurement of Lubricant Generated Insoluble Color Bodies in in-service Turbine Oils using MPC (Membrane Patch Colorimetry).
The method involves extracting insoluble contaminants from a sample on to a membrane patch, the colour of which is then analysed. Results are reported as a ΔE value within the CIELAB scale. Full details on sampling and preparation procedures are available from ASTM International.