What is the principle of capillary zone electrophoresis?

In CZE, a fused silica capillary with ionized silanol groups is filled with a buffer solution. To introduce the analyte into the capillary, a small plug is injected at the proximal tip. This can be achieved either by applying pressure or by utilizing an electric field. The negatively charged SiO-ions attract positively charged cations, forming two layers—a stationary and a diffuse cation layer. When an electric field is applied, the diffuse layer migrates towards the negatively charged cathode, creating an electrophoretic flow that drags the bulk solvent along with it. As a result, cations move towards the cathode, while anions move towards the anode. Cations with higher charge-to-mass ratios separate first, followed by those with lower ratios, neutral species, anions with lower ratios, and finally anions with higher ratios. The speed of electroosmotic flow can be adjusted by changing factors such as pH, voltage, solvent viscosity, and the dielectric constant of the buffer solution to achieve optimal results.