I have prepared the chitosan nanoparticles loaded with natural product (which is soluble in ethanol). i want to study the comulative frequency of in vitro release using PBS (7.4) as the receiving solution. i am expecting to withdraw 5 ml from 20 ml of receiving solution for UV analysis but i don't know the required initial concentration of chitosan loaed nanoparticles to be prepared. please am requesting your help.