I was wondering if it was possible to use the 'Norm nm' and 'Norm Abs' measurements from a nanodrop to determine the concentration of nanoparticles in solution, especially when mixed with other particles in solution?
Well you cannot, unless you have the extinction coefficient of the nanoparticles according to their average size. When having a mixture of nanoparticles, if the other nanoparticles have absorption at you desired wavelength then you are in trouble.