Determining the concentration of lead in a water sample using atomic absorption spectroscopy AAS involves several steps, including sample preparation, instrument calibration, and sample measurement. Here is a step-by-step procedure:1. Sample preparation: a. Collect a representative water sample in a clean, polyethylene bottle. The volume of the sample should be sufficient for analysis, typically around 100-200 mL. b. Preserve the sample by adding a few drops of concentrated nitric acid HNO3 to prevent any precipitation or adsorption of lead on the container walls. Store the sample in a cool, dark place until analysis. c. Before analysis, filter the sample through a 0.45 m membrane filter to remove any suspended particles that may interfere with the AAS measurement.2. Instrument calibration: a. Prepare a series of lead standard solutions with known concentrations, typically in the range of 0.1 to 10 g/mL. Use a lead stock solution 1000 mg/L and dilute it with deionized water and 1% v/v nitric acid to obtain the desired concentrations. b. Set up the atomic absorption spectrometer according to the manufacturer's instructions. Choose the appropriate lamp lead hollow cathode lamp and set the wavelength to 283.3 nm, which is the optimal absorption wavelength for lead. c. Aspirate deionized water into the instrument to obtain a baseline reading. d. Aspirate each standard solution into the instrument and record the absorbance values. Plot the absorbance values against the corresponding lead concentrations to create a calibration curve.3. Sample measurement: a. Aspirate the filtered water sample into the instrument and record the absorbance value. b. Compare the absorbance value of the sample to the calibration curve to determine the concentration of lead in the water sample. c. If the sample concentration is outside the calibration range, dilute the sample with deionized water and 1% v/v nitric acid to bring it within the range, and repeat the measurement. Be sure to account for the dilution factor when calculating the final lead concentration.4. Quality control: a. Analyze a blank deionized water with 1% v/v nitric acid and a standard reference material SRM with a known lead concentration to ensure the accuracy and precision of the method. b. If the measured values for the blank and SRM are within acceptable limits, the results for the water sample can be considered reliable.5. Report the results: a. Report the concentration of lead in the water sample in units of g/L or mg/L, depending on the level of contamination. b. Include information about the method, instrument settings, calibration curve, and quality control measures in the report.Remember to follow safety guidelines and wear appropriate personal protective equipment PPE during the entire procedure.