Atomic absorption spectroscopy AAS is a widely used analytical technique for determining the concentration of specific elements, such as lead Pb , in various samples, including water. To quantitatively determine the concentration of lead in a water sample taken from a local river using AAS, follow these steps:1. Sample collection and preparation: a. Collect a representative water sample from the river using a clean, pre-rinsed container. b. Filter the sample to remove any suspended particles using a suitable filter, such as a 0.45 m membrane filter. c. Acidify the filtered sample with concentrated nitric acid HNO3 to a pH of around 2 to prevent precipitation and adsorption of lead onto the container walls. Store the sample in a polyethylene or polypropylene container.2. Instrument calibration: a. Prepare a series of lead standard solutions with known concentrations by diluting a certified lead standard stock solution with deionized water. The concentration range should encompass the expected concentration of lead in the river water sample. b. Acidify the standard solutions with concentrated nitric acid to match the pH of the sample. c. Measure the absorbance of each standard solution using the AAS instrument, ensuring that the instrument is set to the appropriate wavelength for lead typically 283.3 nm . d. Plot a calibration curve by plotting the absorbance values against the corresponding lead concentrations. The curve should be linear, and the correlation coefficient R should be close to 1.3. Sample analysis: a. Measure the absorbance of the acidified river water sample using the AAS instrument at the same wavelength used for the calibration standards. b. Determine the concentration of lead in the sample by interpolating the measured absorbance value on the calibration curve.4. Verification and quality control: a. Analyze a certified reference material CRM with a known lead concentration to verify the accuracy of the method. b. Perform a spike recovery test by adding a known amount of lead to a portion of the river water sample and analyzing it using the same procedure. The recovery should be within an acceptable range e.g., 80-120% . c. Analyze duplicate samples to assess the precision and repeatability of the method.5. Reporting results: a. Report the lead concentration in the river water sample, including the units e.g., g/L or ppb . b. Include information about the sample collection, preparation, and analysis procedures. c. Report the results of the quality control tests, such as the CRM analysis, spike recovery, and duplicate analysis, to demonstrate the accuracy and precision of the method.By following these steps, you can use atomic absorption spectroscopy to accurately and reliably determine the concentration of lead in a water sample taken from a local river.