How the use of a short channel can improve the separation efficiency of nanoparticles in asymmetrical flow field-flow fractionation

•The use of a shorter channel improves the separation efficiency of nanoparticles in AF4.•Theoretical aspects have been considered to justify experimental results obtained.•Non-equilibrium diffusion is the most relevant component during separation.•Polystyrene particles have been used as model.•The separation of a mixture of TiO2 nanoparticles has been carried out.