Polarography is an electroanalytical technique that can be used to determine the concentration of various ions, including lead ions, in a sample of water. The technique is based on the measurement of current as a function of applied potential. Here's a step-by-step guide on how to use polarography to determine the concentration of lead ions in a water sample:1. Prepare the sample: First, collect the water sample and filter it to remove any suspended particles. If necessary, acidify the sample with a small amount of concentrated nitric acid to dissolve any precipitated lead salts.2. Prepare the polarographic cell: The cell typically consists of a dropping mercury electrode DME as the working electrode, a reference electrode e.g., a saturated calomel electrode, SCE , and an auxiliary electrode e.g., a platinum wire . Fill the cell with a suitable supporting electrolyte, such as a mixture of potassium chloride and hydrochloric acid, which provides a constant ionic strength and stable background current.3. Add the sample to the cell: Introduce an aliquot of the water sample into the polarographic cell. Make sure to stir the solution continuously to ensure proper mixing and mass transport of the analyte to the electrode surface.4. Perform the polarographic analysis: Apply a potential to the working electrode and gradually increase it from a negative value to a more positive value. As the potential increases, the lead ions in the sample will be reduced at the surface of the DME, producing a current. Record the current as a function of the applied potential to obtain a polarogram.5. Identify the lead peak: In the polarogram, you will observe a current peak corresponding to the reduction of lead ions Pb2+ to Pb . The potential at which this peak occurs is characteristic of lead and can be used to confirm its presence in the sample.6. Calibration curve: Prepare a series of standard solutions containing known concentrations of lead ions. Perform polarographic analysis on each standard solution and plot the peak current as a function of lead concentration. This will give you a calibration curve.7. Determine the concentration of lead ions in the sample: Measure the peak current corresponding to the lead reduction in the water sample's polarogram. Using the calibration curve, find the concentration of lead ions that corresponds to the measured peak current.8. Calculate the concentration of lead ions in the original water sample: If you diluted the water sample before introducing it into the polarographic cell, make sure to account for the dilution factor when calculating the concentration of lead ions in the original sample.By following these steps, you can successfully use polarography to determine the concentration of lead ions in a water sample.