Comparison of Microwave vs. Hot-Plate Digestion for Nine Real-World River Sediments
- Yu-Ling Wei *,
- Huey-Meei Shyu and
- Kun-Long Joehuang
USEPA Methods 3051 and 3050 were followed to digest five heavy metals from nine real-world and one SRM sediments. The extracted heavy metals were analyzed using flame atomic absorption spectroscopy (FAAs). The SRM 2704 and the real-world samples were simultaneously acid digested on a hot-plate and in a microwave digester. For all five heavy metals, the results indicated that the percent bias, which was defined as the value of (Method 3050 minus Method 3051) divided by Method 3051, was high for the real-world sediments from some sampling locations. Cadmium and nickel generally gave high “positive biases”; while Pb and Cu had a tendency to give greater “negative biases”. For Zn, the positive and negative biases were balanced. The reason for the scattering of percent biases for all five heavy metals might be attributed to: (a) the complex matrices of the solid materials in the sediments, which were conceptually classified into five different fractions, and (b) the difference in acid type, acid concentration, digestion temperature, and digestion pressure. Consequently, the substitution between these two methods might be quite misleading in some cases, and decisions about site cleanup levels could be totally different due to these biases, especially for cadmium-contaminated sites.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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