Polarography is an electroanalytical technique used to determine the concentration of metal ions in a given sample. It is based on the principle of measuring the current produced by the reduction or oxidation of the analyte metal ion at a dropping mercury electrode DME or other suitable electrodes. The current is measured as a function of the applied potential, and the resulting current-potential curve polarogram is used to determine the concentration of the metal ion.Here are the steps to determine the concentration of a certain metal ion using polarography:1. Prepare the sample: Dissolve the sample in a suitable solvent, usually an aqueous solution, and add an appropriate supporting electrolyte. The supporting electrolyte should not react with the metal ions or interfere with the polarographic analysis.2. Set up the polarographic cell: The cell consists of a working electrode DME , a reference electrode e.g., Ag/AgCl or calomel electrode , and an auxiliary electrode e.g., platinum wire . The electrodes are immersed in the sample solution.3. Apply potential and measure current: A potential is applied between the working and reference electrodes, and the current flowing through the cell is measured. The potential is varied linearly or in steps, and the current is recorded as a function of the applied potential.4. Obtain the polarogram: The resulting current-potential curve polarogram shows a characteristic wave or peak for the metal ion of interest. The peak current ip is proportional to the concentration of the metal ion in the sample.5. Calibration and quantification: Prepare a series of standard solutions containing known concentrations of the metal ion and perform polarographic measurements for each standard. Plot the peak current ip as a function of the metal ion concentration to obtain a calibration curve. Determine the concentration of the metal ion in the unknown sample by comparing its peak current with the calibration curve.The choice of supporting electrolyte is crucial for the precision and accuracy of the polarographic analysis. The supporting electrolyte should fulfill the following criteria:1. High ionic strength: A high ionic strength reduces the resistance of the solution and ensures a stable and well-defined polarographic wave or peak.2. Inertness: The supporting electrolyte should not react with the metal ions or other components in the sample. It should also not interfere with the electrode processes.3. Suitable pH: The pH of the solution should be adjusted to ensure the metal ions are in a suitable oxidation state for the polarographic analysis. The supporting electrolyte should not alter the pH of the solution significantly.4. Minimal background current: The supporting electrolyte should not contribute to the background current, which can affect the precision and accuracy of the polarographic measurements.By carefully selecting the supporting electrolyte and optimizing the experimental conditions, it is possible to achieve high precision and accuracy in the determination of metal ion concentrations using polarography.