To determine the concentration of fluoride ions in a sample of drinking water using a fluoride ion-selective electrode ISE , you will need to follow these steps:1. Calibration: Prepare a series of fluoride ion standard solutions with known concentrations e.g., 0.1, 1, 10, and 100 ppm . Measure the potential in millivolts of each standard solution using the fluoride ISE and a reference electrode. Plot the potential y-axis against the logarithm of the fluoride concentration x-axis to create a calibration curve.2. Sample preparation: Collect a representative sample of the drinking water. If the water contains high levels of interfering ions e.g., hydroxide, carbonate, or phosphate , you may need to pretreat the sample with a buffer solution to minimize interferences.3. Measurement: Immerse the fluoride ISE and reference electrode in the drinking water sample. Allow the potential to stabilize, and then record the potential in millivolts .4. Calculation: Use the recorded potential of the drinking water sample and the calibration curve to determine the logarithm of the fluoride concentration. Convert the logarithm to the actual fluoride concentration in ppm or mg/L using the antilog function.Keep in mind that the accuracy of the fluoride ISE measurement depends on proper calibration, sample preparation, and minimizing interferences. Additionally, the fluoride ISE should be properly maintained and stored according to the manufacturer's instructions to ensure reliable results.