EPA-RCA: 7470A: Mercury by Manual Cold-Vapor Technique
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Official Method Name
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Mercury in Liquid Waste (Manual Cold-Vapor Technique) |
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Current Revision
| Revision 1, September 1994 |
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Media
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VARIOUS |
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Instrumentation
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Cold Vapor Atomic Absorption |
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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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Aqueous samples are digested with sulfuric acid, nitric acid, potassium permanganate, and potassium persulfate in order to oxidize the organo-mercury compounds to the mercuric ion. Once the digested samples have cooled, sodium chloride-hydroxylamine sulfate is added to reduce excess permanganate. Stannous sulfate is then added to the samples for the reduction to elemental mercury which is immediately measured by a cold-vapor atomic absorption spectrophotometer (or equivalent instrument). |
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Scope and Application
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This method determines the concentration of mercury in aqueous wastes, mobility-procedure abstracts, and ground water. It can also be used for analyzing certain solid and sludge-type wastes, however, Method 7471 is recommended for these matrices. |
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Applicable Concentration Range
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Not Available. |
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Interferences
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(A) Matrix interferences: Sulfide as sodium sulfide may possibly interfere with mercury, however, potassium permanganate is added to eliminate interferences from concentrations as high as 20 mg/L. Copper is also known to cause interference, however, concentrations as high as 10 mg/L have shown to have no effect on mercury recovery. Seawaters, brines, and industrial effluents high in chlorides require additional amounts of permanganate and hydroxylamine sulfate to ensure the absence of free chlorine which interfere with mercury detection. In addition, air space in the BOD bottle must be purged before adding stannous chloride. Certain volatile organic compounds may also cause interference. A preliminary run without reagents should determine their presence. |
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Quality Control Requirements
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Refer to section 8.0 of Method 7000. |
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Sample Handling
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Aqueous samples must be acidified to a pH < 2 with nitric acid. Non-aqueous samples shall be refrigerated and analyzed as soon as possible. |
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Maximum Holding Time
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Preserved samples: 28 days. |
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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Method 7470A |
