There has been a great interest in uniformly dispersed suspensions of colloidal gold or nanoparticles right from ancient times. Colloidal gold was initially used in stained glass, potions and other artistic expressions. Presently researchers are studying gold nanoparticle dispersions and one needs to note that control of morphology and size of particles is highly critical. The National Institute of Standards and Technology (NIST) has developed reference materials (RMs) of gold nanoparticles that are around 10, 30, and 60 nm. This application note discusses a technique and shows results from a study analyzing the NIST RM samples.