EPA-NERL: 200.12: Trace Elements in Marine Waters by GFAA
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Official Method Name
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Determination of Trace Elements in Marine Waters by Stabilized Temperature Graphite Furnace Atomic Absorption |
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Current Revision
| Revision 1.0, September 1997 |
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Media
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WATER |
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Instrumentation
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Graphite Furnace-Atomic Absorption Spectrometer |
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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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A sample is refluxed with nitric acid and then centrifuged or particulate is allowed to settle. An aliquot of treated sample is transferred to a stabilized temperature platform graphite furnace atomic absorption (STPGFAA) system. The aliquot is dried at a low temperature, charred/ashed to remove interferences, atomized, and concentrations of atomized elements are determined using a STPGFAA spectrophotometer. |
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Scope and Application
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This method determines total recoverable elements in marine waters, including estuarine, ocean, and brines with salinites of up to 35 ppt. |
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Applicable Concentration Range
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Not Provided |
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Interferences
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(A) Blackbody radiation: Emission of blackbody radiation from the oven can interfere with absorbance measurements. (B) Elemental interferences: Spectral overlap of elemental absorptions can occur, but are relatively uncommon. Appropriate furnace temperature programs and high purity lamps can reduce interferences. (C) Molecular interferences: More common than elemental interferences, they can be reduced by using matrix modifiers, selective volatilization, background correctors, and appropriate furnace charring conditions. Note: The correct charring temperature is critical when analyzing saline waters. (D) Matrix interferences: Some matrix components can inhibit the formation of free atoms. (E) Memory interferences: Analyte can carry over in the furnace between runs. Use low concentration samples to ensure that analytes do not carry over. (F) Specific element interferences: Cadmium, selenium, and arsenic have characterized interferences and suggested interference removal procedures. |
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Quality Control Requirements
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Initial demonstration of laboratory capability and the periodic analysis of laboratory reagent blanks, fortified blanks, and other laboratory solutions as a continuing check on performance. |
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Sample Handling
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For the determination of total recoverable elements in aqueous samples, acidify with (1+1) nitric acid (ultra high purity) at the time of collection to pH <2 (normally 3 mL of acid per liter of samples is sufficient). The sample should not be filtered prior to analysis. |
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Maximum Holding Time
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6 months. |
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Relative Cost
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$201 to $400 |
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Sample Preparation Methods
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