TEM could be used to get the size and shape of your particles, however, the high concentration will lead to getting an unclear or dark image, but it's worth to try.

Do your samples scatter? Have you tried passing a laser beam (pointer) to confirm? Do you have access to laser diffraction?

No Brownian motion and therefore no diffusion coefficient and therefore no ability to apply the Stokes-Einstein equation....

This will apply for acoustic measurements as well.

I assume you mean destabilize in your phrase 'since dilution will stabilize the system'. Remember that DLS and mobility measurements assume no particle-particle interactions for 'true' results. Do you have an oil-in-water or water-in-oil emulsion? Dilution in the mother liquor usually preserves stability. What is the viscosity of your system? Have you measured it? Freeze-fracture is problematic for emulsions. Cryo-EM has been applied successfully for delicate structures such as liposomes. All (particle sizing) measurements on TEM are artifacts of sample preparation and particle selection.

Yes, I meant "destabilize'', sorry for the typographical error. I believe the high amount of surfactant has affected the movement of the particles. We were told to reformulate the microemulsion. Can you suggest accurate ways on how to validate if o/w microemulsion was indeed formed? Thank you sirs.

Please answer my previous questions and then I can begin to help you..

What is the viscosity of your system? Have you measured it?

A picture of your system will be useful. Is it clear or white?

A high amount of surfactant should reduce the viscosity to close to that of water. Have you got an enormous amount of oil in your system? Which oil? Or are you looking at bitumen/asphalt?

Before formuation you should concentrate on HLB and CPP.

Agnishwar Girigoswami Thank you for your undefined acronyms. These are just TLA's....