I have some PNIPAM (Poly(N-isopropylacrylamide)) aqueous solution in which PNIPAM are crosslinked to form spherical microspheres. I want to know the concentration of these microspheres in solution. One way I can think of is to dry the solution out and measure the weight followed by calculating the concentration based on density and volume. Unfortunately, I don't have much solution therefore the weight might be too small to measure. I wonder is there any other method to measure the concentration? Thanks a lot!