I guess if you can somehow separate your nanoparticles  from unconverted PLGA you could measure the yield of the process. Suppose,  your nanophase are in nanosphere/nanoparticle  form, then you can filter out  the precipitation using suitable filter to separate particles from the bulk polymer.  Also, You can use image analysis (SEM/TEM images) to get an idea  about nanoparticles and unconverted polymer.

PLGA is practically insoluble in water, therefor all PLGA is precipitated after water addition, i.e. could be present as nano- or larger particle and maybe on the wall of the container etc. If you want to know it more precisely determine solids content after separation.

Thank you Kulal Mondal and Titus Sobisch for the valuable suggestions. 

PLGA size of the polymer particles to be obtained depends directly on the size of particles or nanoparticles that formed as the PLGA if hydrolyzed by their ester linkages, the measurement of size distribution of polymer nanoparticles suspended It measured by Dinamyc light scattering DLS, and to better check by SEM or TEM.

Dear Anurag,

Usually publications do not mention the yield. However, you can calculate a yield for each batch of NPs from comparison of the mass of NP powder recovered (after lyophilization for example) and the initial mass of the polymer you use to prepare the NPs. But this could lead to a slightly elevated yield due to remained adsorbed surfactant but at least you could have an idea if you are having some variability between different batches (because of repeated centrifugation and re suspension and so on). I used to prepare PLGA NPs without a surfactant in the aqueous phase. In my SEM images a never saw any adsorbed polymer.

Carina

Hello Carina Isabel Correia Crucho 

Exactly, publications do not mention how much polymer has been converted in to the particles. 

The method you explained in your answer can theoretically can tell us the conversion of polymer into nano-particles but experimentally there will  some deviations. 

Thanks a lot for the answer !