Polarography is an electroanalytical technique that can be used to determine the concentration of metal ions in a river water sample. The method is based on the measurement of current as a function of applied potential, which provides information about the reduction and oxidation processes of the analyte. Here are the steps to determine the concentration of a certain metal ion in a river water sample using polarography:1. Sample preparation: Collect the river water sample and filter it to remove any suspended particles. If necessary, acidify the sample with a dilute acid e.g., nitric acid to dissolve any precipitated metal ions and to stabilize the metal ions in solution.2. Electrode preparation: Clean and polish the working electrode usually a dropping mercury electrode or a static mercury drop electrode to ensure a reproducible and well-defined surface.3. Calibration: Prepare a series of standard solutions containing known concentrations of the metal ion of interest. Record the polarograms for each standard solution under the same experimental conditions as the river water sample. Plot the peak current ip as a function of the metal ion concentration to obtain a calibration curve.4. Measurement: Record the polarogram of the river water sample under the same experimental conditions as the calibration standards. Identify the peak corresponding to the metal ion of interest based on its characteristic half-wave potential E1/2 .5. Quantification: Measure the peak current ip of the metal ion in the river water sample and use the calibration curve to determine its concentration.6. Validation: To ensure the accuracy of the results, analyze a certified reference material or spike the river water sample with a known concentration of the metal ion and compare the measured concentration with the expected value.7. Data interpretation: Report the concentration of the metal ion in the river water sample, taking into account any dilution factors and the limit of detection and quantification of the method.By following these steps, you can determine the concentration of a certain metal ion in a river water sample using polarography.