The presence of nitrate ions NO3- in a solution can be identified using an ion-selective electrode ISE in analytical chemistry through the following steps:1. Preparation of the nitrate ion-selective electrode: The nitrate ISE typically consists of a solid-state membrane that selectively interacts with nitrate ions. The most common type of nitrate ISE is based on a PVC polyvinyl chloride membrane containing a nitrate ionophore, which selectively binds to nitrate ions. The electrode also has an internal reference electrode and a filling solution.2. Calibration of the nitrate ISE: Before using the nitrate ISE to measure the concentration of nitrate ions in an unknown solution, it must be calibrated. Prepare a series of standard solutions with known concentrations of nitrate ions. Immerse the nitrate ISE and a reference electrode e.g., Ag/AgCl in each standard solution, and measure the potential voltage difference between the two electrodes. Plot the measured potentials against the logarithm of the nitrate ion concentrations to obtain a calibration curve.3. Measurement of the unknown solution: Rinse the nitrate ISE and reference electrode with distilled water and immerse them in the unknown solution. Allow the potential to stabilize, and then record the potential difference between the nitrate ISE and the reference electrode.4. Determination of nitrate ion concentration: Use the calibration curve obtained in step 2 to determine the concentration of nitrate ions in the unknown solution. Locate the measured potential on the calibration curve and find the corresponding nitrate ion concentration.5. Validation and quality control: To ensure the accuracy of the results, it is essential to perform validation and quality control checks. Analyze a known standard solution and a blank nitrate-free solution alongside the unknown sample to verify the accuracy and precision of the measurements.By following these steps, the presence and concentration of nitrate ions in a solution can be identified using an ion-selective electrode in analytical chemistry.