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 to the solution.
3. Repeat step 2 until no more foaming occurs and the solution becomes clear. Then, remove the beaker from the heating plate and let it cool further.
4. Filter the resulting solution and dilute it with deionized water for analysis.
The cadmium content is measured using an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES).
Lead Test Method - US EPA 3050 B
1. Place the sample in a beaker and add nitric acid (HNO3), then heat the mixture.
2. Allow the solution to cool to room temperature, then add hydrogen peroxide (H2O2) and continue heating until the reaction completes and foaming stops.
3. Repeat step 2 if necessary to ensure complete digestion.
4. Cool the solution again, add hydrochloric acid (HCl), and heat until the process is complete.
5. Filter the solution, dilute 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 reaction vessel. Add concentrated sulfuric acid and hydrogen peroxide.
2. Put the reaction vessel into a microwave digester and heat until the sample is completely dissolved.
3. Filter the solution, dilute the filtrate with deionized water, and measure the mercury content using ICP-AES.
Hexavalent Chromium Test Method - US EPA 3060 A
1. Add a digestion solution, magnesium chloride (MgCl2), and phosphate buffer to the sample.
2. Heat the mixture, allow it to cool, filter, and then add nitric acid (HNO3) for further processing.
3. Add two additional reagents: carbachol solution and sulfuric acid (H2SO4), and let the mixture stand for 5–10 minutes to observe a color change.
4. Measure the absorbance at a wavelength of 540 nm using a UV spectrophotometer.
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