The concentration of chloride ions in seawater varies depending on the location and depth, but on average, it is approximately 19,000 mg/L or 19 g/L grams per liter . This is equivalent to about 0.54 mol/L moles per liter of chloride ions.To determine the concentration of chloride ions in a seawater sample using an ion-selective electrode ISE , follow these steps:1. Calibration: Prepare a series of chloride ion standard solutions with known concentrations, covering the expected range of the seawater sample e.g., 0.1, 0.3, 0.5, 0.7, and 1.0 mol/L . Measure the potential voltage of each standard solution using the chloride ISE and a reference electrode. Plot the measured potentials against the logarithm of the chloride ion concentrations to create a calibration curve.2. Sample preparation: Collect a representative seawater sample and filter it through a 0.45 m filter to remove any suspended particles. Dilute the sample if necessary to bring the chloride concentration within the range of the calibration curve.3. Sample measurement: Measure the potential of the seawater sample using the chloride ISE and the reference electrode. Ensure that the electrodes are properly rinsed and equilibrated between measurements to avoid contamination.4. Data analysis: Use the measured potential of the seawater sample and the calibration curve to determine the logarithm of the chloride ion concentration. Convert the logarithm to the actual chloride ion concentration.5. Quality control: To ensure the accuracy of the results, analyze a known standard solution and a blank deionized water alongside the seawater sample. The measured values should be within the acceptable range of the known concentrations.By following these steps, you can accurately determine the concentration of chloride ions in a seawater sample using an ion-selective electrode.