I don't know if I got your point or not. I assume you want to use a UV and detect the size distribution of your sample. Basically, one method could be the combination of Beer-lambert law and Stokes’ Law, based on sedimentation rate, indicating larger particles sediment faster than smaller ones, and their corresponding transmittance is also lower compared to the smaller particles. A graph representing time and absorbance and some correlation and integration could help to get the idea of particle size distribution. Don't forget that we are should consider the assumption of Beer-Lambert Law, and your sample should be dispersed in a liquid that minimizes agglomeration and can be dispersed well.