EPA-EAD: 1637: Determination of Trace Elements in Ambient Waters by Chelation and GFAA
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Official Method Name
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Determination of Trace Elements in Ambient Waters by Off-Line Chelation Preconcentration and Stabilized Temperature Graphite Furnace Atomic Absorption |
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Current Revision
| January 1996 |
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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 acidified and solubilized by gentle refluxing (if total recoverable elements are desired). Elements in the sample are concentrated using off-line chelating resin column. The concentrated extracts are analyzed using stabilized temperature graphite furnace atomic absorption (GFAA). |
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Scope and Application
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This method determines dissolved elements in ambient waters at EPA water quality criteria (WQC) levels. It may also be used for determination of total recoverable element concentrations in these waters. |
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Applicable Concentration Range
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Not Available. |
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Interferences
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(A) Contamination by carryover: Contamination may occur when a sample containing low concentrations of metals is processed immediately after a sample containing relatively high concentrations of these metals. To reduce rinse the sampling system between samples with dilute acid and reagent water. (B) Contamination by samples: Significant laboratory or instrument contamination may result when untreated effluents, in-process waters, landfill leachates, and other samples containing high concentrations of inorganic substances are processed and analyzed. (C) Contamination by indirect contact: Apparatus that may not directly come in contact with the samples may still be a source of contamination. It is imperative that every piece of the apparatus that is directly or indirectly used in the collection, processing, and analysis of ambient water samples be cleaned. (D) Contamination by airborne particulate matter: Samples may be contaminated by airborne dust, dirt, particles, or vapors from unfiltered air supplies; nearby corroded or rusted pipes, wires, or other fixtures; or metal-containing paint. (E) Spectral interferences: Spectral interferences caused by the absorbance of light by a molecule or atom that is not the analyte of interest or emission from black body radiation. (F) Matrix interferences: Matrix interferences caused by sample components that inhibit the formation of free atomic analyte atoms during the atomization cycle. (G) Memory effects (GFAA) : Results from analyzing a sample containing a high concentration of an element (typically a high atomization temperature element) that cannot be removed quantitatively in one complete set of furnace steps. (H) Competing chelators: Low recoveries may be encountered in the preconcentration cycle if the trace elements are complexed by competing chelators (humic/fulvic) in the sample or are present as colloidal material. (I) Memory effects (Chelating System; Preconcentration). |
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Quality Control Requirements
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The minimum requirements consist of an initial demonstration of laboratory capability, analysis of samples spiked with metals of interest to evaluate and document data quality, and analysis of standards and blanks as tests of continued performance. |
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Sample Handling
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Collect samples as described in EPA Method 1669. For dissolved metals, samples and field blanks are filtered through a 0.45 um capsule filter at the field site. Preservation of samples and field blanks for both dissolved and total recoverable elements may be performed in the field when the samples are collected or in the laboratory. Preservation involves the addition of 10% HNO3 to bring the sample to pH < 2. For samples received at neutral pH, approximately 5 mL of 10% HNO3 per liter will be required. Store preserved sample for a minimum of 48 hours at 0-4oC. Sample bottles should be stored in polyethylene bags at 0-4oC until analysis. |
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Maximum Holding Time
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6 months (after preservation) |
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Relative Cost
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$51 to $200 |
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Sample Preparation Methods
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None. |
