The concentration of lead in a water sample can be determined using atomic absorption spectroscopy AAS by following these general steps:1. Sample preparation: Collect a representative water sample and filter it to remove any suspended particles. Acidify the sample with a small amount of concentrated nitric acid HNO3 to dissolve any lead precipitates and to prevent microbial growth during storage. Store the sample in a clean, polyethylene container until analysis.2. Calibration: Prepare a series of lead standard solutions with known concentrations by diluting a certified lead standard stock solution with deionized water. Acidify the standard solutions with the same concentration of nitric acid as the sample. Measure the absorbance of each standard solution using the AAS instrument and plot a calibration curve of absorbance versus lead concentration.3. Sample analysis: Dilute the acidified water sample, if necessary, to bring the lead concentration within the range of the calibration curve. Measure the absorbance of the diluted sample using the AAS instrument. Determine the lead concentration in the sample by comparing its absorbance to the calibration curve.4. Quality control: Analyze a blank deionized water with the same concentration of nitric acid as the sample and a spiked sample a known amount of lead added to a portion of the water sample to ensure the accuracy and precision of the method.Factors to consider when preparing the sample and setting up the instrument for analysis include:- Selection of the appropriate AAS technique: Flame AAS FAAS or graphite furnace AAS GFAAS can be used for lead analysis. GFAAS is more sensitive and suitable for trace-level analysis, while FAAS is more suitable for higher concentrations.- Wavelength selection: Choose the optimal wavelength for lead detection usually around 283.3 nm to maximize sensitivity and minimize interference from other elements.- Matrix effects: The presence of other elements in the sample may cause spectral interferences or change the sample's viscosity, affecting the AAS measurement. Use matrix-matched calibration standards or a method of background correction to minimize these effects.To compare the results to regulatory limits for lead in drinking water and determine whether the sample is safe for consumption, follow these steps:1. Check the regulatory limit for lead in drinking water in your country or region. For example, the United States Environmental Protection Agency EPA has set the action level for lead at 15 parts per billion ppb or 0.015 mg/L.2. Calculate the lead concentration in the original water sample by taking into account any dilution factors used during sample preparation and analysis.3. Compare the calculated lead concentration to the regulatory limit. If the lead concentration is below the limit, the water sample is considered safe for consumption. If the concentration exceeds the limit, further investigation and possible remediation actions may be required to ensure safe drinking water.