The working of pH probes is based on the principle of ion exchange. The glass membrane of the pH probe is made of a special type of glass that is sensitive to changes in the hydrogen ion concentration of the solution being measured. The hydrogen ions in the solution interact with the glass membrane, causing an exchange of ions at the surface of the membrane.

As hydrogen ions (H+) in the solution interact with the glass membrane, they replace the sodium ions (Na+) or other positively charged ions in the glass membrane, resulting in an electrical potential difference across the membrane. This potential difference is then measured by the reference electrode, which acts as a stable reference point.

The reference electrode typically contains a reference solution that has a known and stable potential. This reference potential is used as a comparison against the potential generated by the glass electrode, and the difference between the two potentials is used to determine the pH of the solution being measured.

pH probes need to be calibrated regularly using solutions with known pH values to establish a calibration curve that relates the potential difference to the corresponding pH values. This allows for accurate and reliable pH measurements.

It's important to handle pH probes carefully, avoiding any contact with hard or abrasive surfaces that may damage the delicate glass membrane. Regular cleaning and proper storage in a suitable electrolyte solution can help maintain the performance and longevity of pH probes. Following manufacturer's instructions and best practices for calibration and maintenance is crucial for obtaining accurate and consistent pH measurements in various applications.