Polarography is an electroanalytical technique used to determine the concentration of various ions, including copper ions Cu2+ , in a given 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 or a static mercury drop electrode SMDE as the working electrode, a reference electrode, and an auxiliary electrode. Here's a step-by-step guide on how to quantify the concentration of Cu2+ in a sample using polarography:1. Prepare the sample: First, you need to prepare the sample by dissolving it in a suitable solvent, usually an aqueous solution containing a supporting electrolyte. The supporting electrolyte helps to maintain a constant ionic strength and minimizes the migration of ions towards the electrode. Common supporting electrolytes for Cu2+ analysis are potassium chloride KCl or sodium acetate CH3COONa .2. Set up the polarographic cell: The polarographic cell consists of a working electrode DME or SMDE , a reference electrode e.g., saturated calomel electrode, SCE , and an auxiliary electrode e.g., platinum wire . The electrodes are connected to a potentiostat, which controls the applied potential and measures the current.3. Deoxygenate the sample: Before starting the analysis, it is essential to remove dissolved oxygen from the sample, as it can interfere with the reduction of Cu2+ ions. This can be done by purging the sample with an inert gas, such as nitrogen or argon, for several minutes.4. Perform the polarographic analysis: Start the potentiostat and begin scanning the potential from a positive value towards a negative value. As the potential becomes more negative, Cu2+ ions will be reduced at the working electrode, generating a current. The current will increase as more Cu2+ ions are reduced, and then level off as the concentration of Cu2+ ions near the electrode surface becomes depleted. This results in a sigmoidal-shaped curve called a polarogram.5. Identify the half-wave potential: The half-wave potential E1/2 is the potential at which half of the maximum current is observed. It is characteristic of the analyte Cu2+ in this case and can be used to confirm its presence in the sample.6. Construct a calibration curve: To quantify the concentration of Cu2+ in the sample, you need to create a calibration curve. This involves analyzing a series of standard solutions containing known concentrations of Cu2+ and plotting the peak current or half-wave current as a function of Cu2+ concentration. The resulting calibration curve should be linear, and its equation can be used to determine the concentration of Cu2+ in the unknown sample.7. Determine the concentration of Cu2+ in the sample: Measure the peak current or half-wave current for the unknown sample and use the calibration curve equation to calculate the concentration of Cu2+ ions.8. Validate the results: To ensure the accuracy of your results, it is recommended to perform a recovery test by spiking the sample with a known amount of Cu2+ and analyzing it again. The recovery should be within an acceptable range e.g., 95-105% .By following these steps, you can successfully quantify the concentration of copper ions Cu2+ in a given sample using polarography.