Capillary electrophoresis and asymmetric flow field-flow fractionation for size-based separation of engineered metallic nanoparticles: AÂ critical comparative review

In the characterization of nanomaterials, size and size distribution are among the most important parameters. A high-resolution technique is essential for the accurate determination of size distribution for a polydisperse nanoparticle suspension. Although there are many size-based separation techniques available for this purpose, the open channel designs of capillary electrophoresis (CE) and asymmetric flow field-flow fractionation (AF4) provide excellent resolution and sample recovery. AF4 is a diffusion-based separation technique for colloidal particles with an analytical range from a few nanometers to several microns. Capillary electrophoresis separates particles based on their electrophoretic mobility (charge to size ratio) making CE applicable for charged particles. These two techniques can be used for the size-based separation of metallic nanoparticles depending on the surface charge and physicochemical properties of the surrounding medium. The purpose of this work is to provide a comprehensive discussion and comparison of CE and AF4 for the determination of the size and size distribution of engineered metallic nanoparticles.