To determine the concentration of lead in a water sample using atomic absorption spectroscopy AAS , follow these steps:1. Sample collection and preparation: Collect a representative water sample from the source. The sample should be stored in a clean, polyethylene or glass container with a tight-fitting lid. If the analysis is not performed immediately, the sample should be preserved by adding a few drops of concentrated nitric acid HNO3 to prevent any precipitation or adsorption of lead onto the container walls.2. Digestion if required : In some cases, the water sample may contain particulate matter or complex lead species that need to be digested before analysis. To do this, add a mixture of concentrated nitric acid HNO3 and hydrogen peroxide H2O2 to the sample and heat it gently until the solution becomes clear. After cooling, filter the solution to remove any remaining particulate matter.3. Calibration: Prepare a series of standard lead solutions with known concentrations by diluting a lead standard stock solution with deionized water. These standard solutions will be used to create a calibration curve for the atomic absorption spectrometer.4. Instrument setup: Set up the atomic absorption spectrometer according to the manufacturer's instructions. Choose the appropriate lamp hollow cathode lamp or electrodeless discharge lamp for lead analysis, and set the wavelength to 283.3 nm, which is the optimal wavelength for lead determination.5. Blank and standard measurements: Measure the absorbance of a blank solution deionized water and the prepared lead standard solutions using the AAS instrument. Record the absorbance values for each standard solution.6. Calibration curve: Plot the absorbance values against the corresponding lead concentrations of the standard solutions. Fit a linear regression line to the data points, and calculate the equation of the line y = mx + b , where y is the absorbance, x is the lead concentration, m is the slope, and b is the intercept.7. Sample measurement: Measure the absorbance of the prepared water sample using the AAS instrument. If the sample's absorbance is outside the range of the calibration curve, dilute the sample with deionized water and re-measure the absorbance.8. Concentration calculation: Use the equation of the calibration curve to calculate the lead concentration in the water sample. If the sample was diluted, adjust the concentration calculation accordingly.9. Quality control: To ensure the accuracy of the results, analyze a quality control sample with a known lead concentration alongside the water sample. The measured concentration of the quality control sample should be within an acceptable range of its known concentration.By following these steps, you can accurately determine the concentration of lead in a water sample using atomic absorption spectroscopy.