Polarography is an electroanalytical technique that can be used to determine the concentration of lead ions in a water sample. It is based on the measurement of current as a function of applied potential. The technique involves the use of a dropping mercury electrode DME as the working electrode, a reference electrode, and an auxiliary electrode. Here is a step-by-step procedure to determine the concentration of lead ions in a water sample using polarography:1. Prepare the water sample: Collect the water sample and filter it to remove any suspended particles. If the sample has a high concentration of dissolved organic matter, it may be necessary to pretreat the sample with an oxidizing agent, such as potassium permanganate, to remove the organic matter.2. Prepare the polarographic cell: Set up the polarographic cell with a dropping mercury electrode DME as the working electrode, a reference electrode e.g., a saturated calomel electrode or silver/silver chloride electrode , and an auxiliary electrode e.g., a platinum wire . Fill the cell with a supporting electrolyte solution, such as 0.1 M KCl, which helps to maintain a constant ionic strength and minimize the resistance of the solution.3. Add the water sample: Add a known volume of the water sample to the polarographic cell. Make sure the sample is well mixed with the supporting electrolyte.4. Deoxygenate the sample: Oxygen can interfere with the polarographic analysis, so it is essential to remove it from the sample. This can be done by purging the sample with an inert gas, such as nitrogen or argon, for several minutes.5. Perform the polarographic analysis: Apply a potential to the working electrode and gradually increase it from a negative value to a positive value. As the potential increases, the current will also increase when the potential reaches a value at which the lead ions are reduced at the electrode surface. This reduction will produce a characteristic current peak, known as the "half-wave potential" E1/2 , which is specific to the lead ions.6. Calibration: To determine the concentration of lead ions in the sample, you need to establish a calibration curve. Analyze a series of standard solutions containing known concentrations of lead ions using the same polarographic procedure. Plot the peak current as a function of the lead ion concentration to create a calibration curve.7. Determine the concentration of lead ions: Measure the peak current for the water sample and use the calibration curve to determine the concentration of lead ions in the sample.8. Report the results: Calculate the concentration of lead ions in the water sample and report the results in the appropriate units e.g., mg/L or ppm .By following these steps, you can successfully determine the concentration of lead ions in a water sample using polarography.