Changing the pH of the buffer solution in capillary electrophoresis CE can significantly affect the separation and detection of ionic species in a given sample. This is because the pH influences the ionization state of the analytes and the electroosmotic flow EOF within the capillary. Here are some ways in which the pH of the buffer solution can impact the separation and detection of ionic species:1. Ionization state of analytes: The pH of the buffer solution determines the ionization state of the analytes ionic species in the sample. At a specific pH, an analyte may exist in its neutral, positively charged, or negatively charged form. The ionization state directly affects the migration of the analytes in the electric field during CE. For example, at a pH below the pKa of an acidic analyte, it will be predominantly protonated and positively charged, while at a pH above its pKa, it will be deprotonated and negatively charged.2. Electroosmotic flow EOF : The pH of the buffer solution also affects the surface charge of the capillary wall. At low pH, the capillary wall will have a positive charge, while at high pH, it will have a negative charge. The surface charge influences the electroosmotic flow, which is the bulk flow of the buffer solution within the capillary due to the movement of counterions in the electric field. The EOF can impact the migration of analytes and their separation efficiency.3. Resolution and selectivity: The pH of the buffer solution can affect the resolution and selectivity of the separation. By adjusting the pH, you can optimize the separation of analytes with different pKa values, as it can influence the degree of ionization and the migration rates of the analytes. The optimal pH for separation is often determined by the pKa values of the analytes and their differences in charge-to-size ratios.4. Detection sensitivity: The pH of the buffer solution can also impact the detection sensitivity of the analytes, particularly when using indirect UV detection. The ionization state of the analytes and the background electrolyte can affect the absorption properties and the overall detection sensitivity.In summary, changing the pH of the buffer solution in capillary electrophoresis can significantly affect the separation and detection of ionic species in a given sample by influencing the ionization state of the analytes, the electroosmotic flow, the resolution and selectivity of the separation, and the detection sensitivity. It is crucial to optimize the pH of the buffer solution to achieve the best separation and detection of the target analytes.