An apparatus and method of chemical mechanical polishing of a wafer employing a device for determining, in-situ, during the CMP process, an endpoint where the process is to be terminated. In the stabilized nanoparticle, chains of the chitosan polymer electrostatically interact with chains of the hydrophilic dispersing agent to form an entangled network between the chitosan polymer and the hydrophilic dispersing agent. If the attenuation values determined thereby are of the same magnitude, then the likelihood of a redirecting process can be excluded.