Ion-selective electrodes ISEs are sensors that can selectively measure the concentration of specific ions in an aqueous solution. In this case, we will use a chloride ion-selective electrode to detect and quantify the concentration of chloride ions in a water sample. Here's a step-by-step procedure to achieve this:1. Calibration: Before measuring the chloride concentration in the water sample, you need to calibrate the chloride ion-selective electrode. Prepare a series of standard solutions with known concentrations of chloride ions e.g., 1, 10, 100, and 1000 mg/L . These solutions can be prepared by dissolving appropriate amounts of sodium chloride NaCl in deionized water.2. Connect the chloride ion-selective electrode to a pH/mV meter or an ion meter, which will display the electrode potential in millivolts or directly convert the potential to concentration in mg/L or ppm .3. Rinse the electrode with deionized water and gently blot dry with a soft tissue or lint-free cloth.4. Immerse the electrode in the first standard solution, and wait for the potential reading to stabilize. Record the potential mV or concentration value displayed on the meter.5. Repeat step 4 for each of the remaining standard solutions.6. Plot a calibration curve by graphing the potential mV values against the logarithm of the chloride concentrations log [Cl-] . If the meter directly displays concentration values, it will internally generate a calibration curve.7. Analyzing the water sample: Collect the water sample to be analyzed and ensure it is well mixed. If the sample has a high concentration of particulate matter, it may be necessary to filter the sample before analysis.8. Rinse the electrode with deionized water and gently blot dry.9. Immerse the electrode in the water sample and wait for the potential reading to stabilize. Record the potential mV or concentration value displayed on the meter.10. If you recorded the potential mV value, use the calibration curve to determine the concentration of chloride ions in the water sample. Locate the potential value on the y-axis, find the corresponding value on the x-axis log [Cl-] , and then convert it back to the linear concentration value.11. Report the concentration of chloride ions in the water sample in the appropriate units e.g., mg/L or ppm .By following these steps, you can use a chloride ion-selective electrode to detect and quantify the concentration of chloride ions in a water sample effectively.