It depends on what instrumentation you have available And what modifications you can make. diffusion of the solvent or solute?

direct measurements like dynamic light scattering or diffusion (PFG) NMR may not be applicable.

some indirect methods like electrochemistry or fluorescence may be better.

Dear all, please check the following documents. My Regards

https://doi.org/10.1029/93JC01858

https://doi.org/10.1111/j.1365-2818.1995.tb03668.x

https://doi.org/10.1016/j.jbbm.2004.03.001

https://doi.org/10.1002/bip.1969.360070111

https://doi.org/10.1021/es025840n

https://doi.org/10.1021/bi00910a019

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2996616/

Navideh Abbasnezhad

See the diffusion feature in gels and a simple diffusion detection method.

.https://www.sibran.ru/upload/iblock/dba/dbacb7e47299ac0b68212eefdcdc5d65.pdf