Therefore, AFFF has been increasingly used to fractionate and characterize metal-based nanoparticles, such as spherical gold or silver particles , online. Besides spherical nanoparticles, CTABcapped as well as PEGylated gold nanorods have successfully been fractionated by AFFF, and the retention behavior was found to be aspect ratio-dependent: nanorods with smaller aspect ratios elute later than those with higher ratios. Thanks to the non-disruptive nature of the AFFF and the coupled characterization methods, in-situ monitoring of gold nanorod growth during seed-mediated synthesis was enabled. So far, AFFF has only been used to fractionate monomeric particles like nanorods or spheres as mentioned above. To the best of our knowledge, this work presents the first study using AFFF to fractionate nanoparticle assemblies such as self-assembled C/S particles.