I don't see another reply, so I will contribute.
I would rather expect problems. I have found that Teflon charges severely in the SEM. It serves very well as an electron mirror. I cannot imagine it would be any better in EPMA at higher currents and voltages. It might take a carbon coating, but I doubt that the result would be good.
I think that you would be more satisfied with the results using epoxy. It is not a thermoplastic material and probably takes the heat of the beam better.
Is there a particular reason that you want to use Teflon? Are the particles flat and at the very surface? If they are not, that will be a problem.