To determine the concentration of sodium ions in a sample of seawater using potentiometry, you can follow these steps:1. Prepare the sample: Collect a representative sample of seawater and filter it to remove any suspended particles or debris. This will ensure that the potentiometric measurement is accurate and not affected by any interfering substances.2. Choose the appropriate electrode: For sodium ion determination, you will need a sodium ion-selective electrode ISE . This electrode is sensitive to the concentration of sodium ions in the solution and generates a potential voltage proportional to the logarithm of the sodium ion activity.3. Calibrate the electrode: Before using the sodium ISE, it must be calibrated to ensure accurate measurements. Prepare a series of sodium ion standard solutions with known concentrations, typically ranging from 0.1 to 100 mM. Measure the potential of each standard solution using the sodium ISE and a reference electrode e.g., Ag/AgCl electrode . Plot the measured potentials against the logarithm of the sodium ion concentrations to obtain a calibration curve.4. Measure the sample potential: Immerse the sodium ISE and the reference electrode in the seawater sample and measure the potential voltage generated by the sodium ions. Ensure that the electrodes are properly placed and that the sample is well-stirred to avoid any concentration gradients.5. Determine the sodium ion concentration: Using the calibration curve obtained in step 3, find the corresponding sodium ion concentration for the measured potential of the seawater sample. This will give you the concentration of sodium ions in the seawater.6. Validate the results: To ensure the accuracy of your measurements, you can perform additional tests, such as comparing the results with other analytical techniques e.g., atomic absorption spectroscopy or ion chromatography or analyzing certified reference materials with known sodium ion concentrations.By following these steps, you can accurately determine the concentration of sodium ions in a seawater sample using potentiometry.