1. Cut the sample into small pieces and place them in a beaker. Add concentrated sulfuric acid and heat until the sample is fully dissolved.
2. Remove the beaker from the heat source, allow it to cool, and then add hydrogen peroxide. This helps break down any remaining organic matter.
3. Repeat step 2 until no more foaming occurs, ensuring the solution becomes clear. Once the reaction is complete, remove the beaker from the heat and let it cool further.
4. Filter the resulting solution and dilute it with deionized water to prepare for analysis.
The cadmium content is then measured using an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES).
Lead Test Method - US EPA 3050B
1. Place the sample in a beaker and add nitric acid (HNO3), then heat the mixture until the sample begins to dissolve.
2. Allow the solution to cool to room temperature, then add hydrogen peroxide (H2O2) and continue heating until the reaction is complete (foam disappears).
3. Repeat step 2 if necessary to ensure full digestion of the sample.
4. Cool the solution again, add hydrochloric acid (HCl), and reheat to complete the digestion process.
5. Filter the solution, dilute it with deionized water, and measure the lead content using ICP-AES.
Mercury Test Method - US EPA 3052
1. Cut the sample into small pieces and place them in a microwave digestion vessel. Add concentrated sulfuric acid and hydrogen peroxide.
2. Seal the vessel and place it in a microwave digester. Heat until the sample is completely dissolved.
3. After cooling, filter the solution and dilute the filtrate with deionized water before measuring the mercury content using ICP-AES.
Hexavalent Chromium Test Method - US EPA 3060A
1. Add a digestion solution, magnesium chloride (MgCl2), and phosphate buffer to the sample to stabilize the chromium compounds.
2. Heat the mixture, allow it to cool, and filter the solution. Then add nitric acid (HNO3) and reheat as needed.
3. Add two portions of carbachol solution and sulfuric acid (H2SO4), and let the mixture stand for 5–10 minutes. The solution should change color, indicating the presence of hexavalent chromium.
4. Measure the absorbance at a wavelength of 540 nm using a UV-Vis spectrophotometer to determine the concentration of hexavalent chromium.
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