Good. Now we know what "grease" actually is (possibly.) Something like a higher alkane, or perhaps, white lithium grease, as Enthalpy: said, a higher lithium soap.
Now, what are you analyzing for? Depending on the analyate and method, you may not have to remove all the grease.
Example: checking for engine wear in lubricating oil is often done with "arcs and sparks" -- essentially just ionizing the grease and contaminants and analyzing the spectra of excited metal ions. Or you can completely destroy the grease and soluble metals with powerful acids for ICP. Or you're doing something else or looking for something else.