EPA: 7196A: Hexavalent chromium in EP/TCLP characteristic extracts and ground waters by colorimetry
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Official Method Name
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Method 7196A: Chromium, Hexavalent (Colorimetric), part of Test Methods for Evaluating Solid Waste, Physical/Chemical Methods |
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Current Revision
| Revision 1, July 1992 |
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Media
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WATER |
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Instrumentation
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Colorimeter |
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Method Subcategory
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Inorganic |
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Method Source
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Citation
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Brief Method Summary
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Dissolved hexavalent chromium, in the absence of interfering amounts of substances such as molybdenum, vanadium, and mercury, is determined colorimetrically by reaction with diphenylcarbazide in acid solution. A redviolet color of unknown composition is produced and its absorbance is measured photometrically at 540 nm. |
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Scope and Application
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This method covers the determination of dissolved hexavalent chromium in EP/TCLP characteristic extracts and ground waters |
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Applicable Concentration Range
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0.5 - 5 mg/L (without dilution) |
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Interferences
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(A) Hexavalent molybdenum, mercury salts, and vanadium also react to form color with the reagent: Concentrations of up to 200 mg/L of molybdenum and mercury can be tolerated. Vanadium interferes strongly, but concentrations up to 10 times that of chromium will not cause trouble. (B) Iron in concentrations greater than 1 mg/L may produce a yellow color, but the ferric iron color is not strong and difficulty is not normally encountered if the absorbance is measured photometrically at the appropriate wavelength. |
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Quality Control Requirements
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Matrix spikes, matrix spike replicates, blanks, alkaline matrix spikes, replicates. |
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Sample Handling
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Store at 4 °C until analyzed. Analyze as soon as possible. |
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Maximum Holding Time
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24 hours |
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Relative Cost
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Sample Preparation Methods
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