Standard Methods: 3030 G: Nitric and Sulfuric Acid Digestion
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Official Method Name
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Nitric Acid-Sulfuric Acid 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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When using more than 100 mL of sample during digestion, determine recovery for each matrix to verify method validity. If sample is not acidified, acidify to methyl orange end point with concentrated H2SO4. To well-mixed sample add 5 mL concentrated HNO3, bring to a slow boil, and evaporate to 15-20 mL. Add 5 mL concentrated HNO3 and 10 mL concentrated H2SO4, and evaporate until dense fumes of SO3 first appear. If solution doesn't clear, add 10 mL concentrated HNO3 and evaporate until SO3 fumes appear. When the solution is clear and no brownish fumes are evident, cool and dilute to 50 mL with water. Heat sample to almost boiling to dissolve soluble salt and filter if needed. Pour filtrate and washings in volumetric flask. Cool, dilute to 100 mL mark, and mix. Remove aliquots or concentrate sample (see abstract in Method 3030-D) for analysis. Samples totally digested by acid digestion techniques yield comparable precision and bias, however, a minimal amount of acid should be used in the digestion as acid adds metals to the sample. |
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Scope and Application
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This method is applicable to the digestion of metals in waste and wastewater samples. |
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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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