Thank you for your reply and for the article. However, I couldn't find the answer in the article. In my understanding, nanoemulsion can enhance bioavailability of a drug by both increasing its dissolution rate because of the large surface area of the droplet and  by increasing its permeation via interaction with the biological membrane. In my case, the nanoemulsion is formed spontaneously from SNEDDS. I want to demonstrate using spectrophotometer that the dissolution rate is indeed increased by measuring the free drug apart from the drug in the nanoemulsion droplet. The measurement is, therefore, done to the drug solution in the donor compartment, not in the receptor compartment as is the case with release study by Franz dffusion cell. Some paper use 0.45 um membrane filter to separate the droplet from the drug solution. However, with size ranges from 30-50 nm the droplet will easily go through the filter, I would say. Please, advise.

Thank you, Tamer. At present, I have circumstances that make uv spectrophotometer the only tool I can use. Certainly, next time I should use HPLC. Thanks for the paper also.