Polarography is an electroanalytical technique that measures the current response of a solution to a varying potential voltage applied to a working electrode. It is a type of voltammetry that uses a dropping mercury electrode DME as the working electrode. The technique can be used to determine the concentration of copper ions in a water sample by following these steps:1. Prepare the water sample: Filter the water sample to remove any suspended particles or debris. If the sample has a high concentration of organic matter or other interfering substances, it may need to be pre-treated, for example, by acid digestion or complexation with a suitable ligand.2. Prepare the polarographic cell: The cell consists of a working electrode DME , a reference electrode usually a saturated calomel electrode, SCE , and an auxiliary counter electrode. Fill the cell with a supporting electrolyte, such as a mixture of potassium chloride KCl and potassium nitrate KNO3 , which provides a constant ionic strength and minimizes the resistance of the solution.3. Add the water sample to the polarographic cell: Dilute the water sample with the supporting electrolyte, if necessary, and add it to the cell. The volume of the sample should be sufficient to cover the tip of the DME.4. Record the polarogram: Apply a potential sweep to the working electrode, starting from a potential more negative than the reduction potential of copper ions. As the potential becomes more positive, the copper ions in the sample will be reduced at the surface of the DME, generating a current. The current will increase as the potential approaches the reduction potential of copper ions and then decrease as the copper ions are depleted at the electrode surface. The resulting current-potential curve is called a polarogram.5. Identify the copper peak: The polarogram will show a peak corresponding to the reduction of copper ions. The potential at which the peak occurs can be compared to the known reduction potential of copper ions to confirm their presence in the sample.6. Calibration: Prepare a series of standard solutions containing known concentrations of copper ions in the same supporting electrolyte as the sample. Record polarograms for each standard solution and plot the peak currents as a function of the copper ion concentration. This will give you a calibration curve.7. Determine the concentration of copper ions in the sample: Measure the peak current for the copper ions in the water sample's polarogram. Use the calibration curve to determine the concentration of copper ions in the sample.8. Calculate the final concentration: If the water sample was diluted before the analysis, multiply the determined concentration by the dilution factor to obtain the original concentration of copper ions in the water sample.By following these steps, you can accurately determine the concentration of copper ions in a water sample using polarography.