To determine the concentration of lead Pb in a water sample using atomic absorption spectroscopy AAS , follow these steps:1. Prepare the water sample: Collect a representative water sample and filter it through a 0.45 m filter to remove any particulate matter. If the sample is highly colored or contains organic matter, you may need to perform a pre-treatment step, such as acid digestion or extraction, to remove potential interferences.2. Prepare calibration standards: Prepare a series of lead calibration standards by diluting a certified lead standard solution with deionized water. The concentration range of the standards should bracket the expected concentration of lead in the water sample. For example, you might prepare standards with concentrations of 0, 1, 5, 10, and 20 g/L.3. Set up the atomic absorption spectrometer: Install the appropriate hollow cathode lamp HCL for lead analysis in the spectrometer. Set the wavelength to the optimal absorption line for lead, which is typically 283.3 nm. Adjust the lamp current, slit width, and other instrument parameters according to the manufacturer's recommendations.4. Measure the absorbance of the calibration standards: Aspirate each calibration standard into the spectrometer's nebulizer and record the absorbance. Make sure to aspirate deionized water between each standard to minimize carryover. Plot the absorbance values versus the lead concentrations to create a calibration curve.5. Measure the absorbance of the water sample: Aspirate the filtered water sample into the nebulizer and record the absorbance. If the absorbance is outside the range of the calibration curve, you may need to dilute the sample or prepare a more concentrated calibration standard.6. Calculate the lead concentration: Use the calibration curve to determine the concentration of lead in the water sample. If you diluted the sample in step 1, make sure to account for the dilution factor in your calculation.7. Quality control: To ensure the accuracy of your results, analyze a quality control sample with a known concentration of lead alongside your water sample. The measured concentration of the quality control sample should be within an acceptable range of its true value.8. Report the results: Report the concentration of lead in the water sample, along with any relevant information about the sample collection, pre-treatment, and analysis. Include the calibration curve and quality control results to demonstrate the accuracy and precision of your measurements.