USGS Mercury Lab, WI: OFR_01-445: Methyl Mercury in Water
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Official Method Name
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Determination of Methyl Mercury by Aqueous Phase Ethylation, Followed by Gas Chromatograpic Separation with Cold Vapor Atomic Fluorescence Detection |
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Current Revision
| April 2001 |
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Media
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WATER |
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Instrumentation
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Cold Vapor Atomic Fluoresence Spectrophotometer |
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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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Samples are distilled to remove potential interferences. Samples are then ethylated and purged onto carbon traps. The traps are thermally dersorbed, separated with a GC column, and detected using Cold Vapor Atomic Fluorescence. |
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Scope and Application
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This method determines methyl mercury in filtered and unfiltered water. |
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Applicable Concentration Range
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0.04 - 5 ng/L |
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Interferences
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The distillation procedure removes potential interferences. In working with samples in the ppq or ppt ranges, the largest problem is contamination. |
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Quality Control Requirements
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The laboratory needs to demonstrate the ability to produce and reproduce reliable data. The standard curve and ethylation (bubbler) blanks should meet data quality objectives (DQOs). In addition, a daily detection limit should be determined with distillation blanks, and performance with environmental samples should be assessed with matrix spike/matrix spike duplicates. |
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Sample Handling
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Contamination is the largest problem. Samples must be collected in rigorously cleaned Teflon bottles using ultra clean sampling techniques. Samples are acidified to 1% v/v using pretested HCl. Store samples in the dark. |
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Maximum Holding Time
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6 Months |
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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