Polarography is an electroanalytical technique that can be used to measure the concentration of lead II ions in a water sample obtained from a contaminated site. The method is based on the measurement of current as a function of applied potential, which provides information about the concentration of the analyte in this case, lead II ions . Here's a step-by-step guide on how to use polarography for this purpose:1. Prepare the sample: Collect the water sample from the contaminated site and filter it to remove any suspended particles or debris. This will help to minimize interferences during the analysis.2. Prepare the electrolyte solution: Prepare a supporting electrolyte solution, which typically contains a high concentration of an inert electrolyte e.g., potassium chloride to maintain a constant ionic strength and minimize the resistance of the solution.3. Prepare the working electrode: Clean the working electrode, which is usually a dropping mercury electrode DME or a static mercury drop electrode SMDE . These electrodes provide a fresh and reproducible surface for each measurement.4. Set up the polarographic cell: Assemble the polarographic cell, which consists of the working electrode, a reference electrode e.g., a saturated calomel electrode , and an auxiliary counter electrode. Fill the cell with the electrolyte solution and add the water sample.5. Perform the polarographic analysis: Apply a potential to the working electrode and gradually increase it from a negative value to a more positive value. This will cause the reduction of lead II ions at the electrode surface, generating a current. Record the current as a function of the applied potential to obtain a polarogram.6. Identify the lead II peak: Analyze the polarogram and identify the peak corresponding to the reduction of lead II ions. This peak will appear at a characteristic potential, which is specific to lead II ions.7. Calibration: Prepare a series of standard solutions containing known concentrations of lead II ions and perform polarographic measurements for each solution. Plot the peak current as a function of the lead II ion concentration to obtain a calibration curve.8. Determine the concentration of lead II ions in the sample: Measure the peak current for the water sample and use the calibration curve to determine the concentration of lead II ions in the sample.9. Quality control: Perform replicate measurements and analyze a blank sample i.e., a sample without lead II ions to ensure the accuracy and precision of the method.By following these steps, you can successfully use polarography to measure the concentration of lead II ions in a water sample obtained from a contaminated site.