Standard Methods: 3030 K: Microwave Assisted Digestion of Metals
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Official Method Name
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Microwave-Assisted Digestion of Samples |
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Current Revision
| Standard Methods Online |
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Media
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WATER |
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Instrumentation
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Preparatory Procedure |
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Method Subcategory
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Sampling/Preparation |
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Method Source
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Citation
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Brief Method Summary
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Transfer 45 mL of well-mixed sample into preweighed digestion vessel. Pipet 5 mL concentrated HNO3 in vessel, and tighten preweighed cap. Distribute samples evenly in carousel. If not enough samples, balance with vessels filled with 45 mL water and 5 mL HNO3. Heat samples to 160 degrees C in 10 minutes, and then, raise temperature to 170 degrees C over the next 10 minutes. Start microwave generator and verify that turntable is turning and exhaust fan is on. Let vessels cool for 5 minutes before removing from unit. Let samples cool, outside of unit, to room temperature. Weigh vessel and record. If the weight of the sample and acid decreased by > 10 percent, discard the sample. Uncap and vent each sample in fume hood, and transfer to plastic bottle. |
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Scope and Application
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This microwave digestion is a closed-vessel procedure and is believed to provide better precision for samples. This digestion is recommended for the analysis of Ag, Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Sb, Se, Tl, V, and Zn. |
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Applicable Concentration Range
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Interferences
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Metals introduced during preliminary treatment from equipment common to environmental labs. |
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Quality Control Requirements
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Check reagent grade acids for purity. Process blanks through all digestion and filtration steps. |
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Sample Handling
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Collect sample in plastic or glass container which has been rinsed with 1+1 HNO3. Adjust the pH of the sample to < 2 with HNO3. For dissolved metals, filter samples immediately. Analyze within 6 months. |
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Maximum Holding Time
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6 months |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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