USGS-NWQL: I-2725-93 (HGA): Silver in Water by Atomic Absorption Spectrophotmetry, Graphite Furnace, Low Ionic Strength
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Official Method Name
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Silver, Atomic Absorption Spectrometry, Graphite Furnace, LIS |
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Current Revision
| 1993 |
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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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Damrau, D.L., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of low-level silver by graphite furnace atomic absorption spectrophotometry: U.S. Geological Survey Open-File Report 93-416 |
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Brief Method Summary
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Silver is determined by atomic absorption spectrophotometry in conjunction with a graphite furnace atomizer containing a pyrolytically coated graphite tube with a graphite platform (Hinderberger and others, 1981). A sample is placed on the graphite platform, and a matrix modifier is added. The sample then is evaporated to dryness, charred, and atomized using maximum power heating. The absorption signal generated during atomization is recorded and compared to a standard curve produced with four standard solutions. Silver may be analyzed on the heated graphite atomizer (HGA) or transverse heated graphite atomizer (THGA) instruments; the only differences are discussed in further detail in the method report. |
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Scope and Application
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This method is used to determine silver in samples of low ionic strength water (specific conductivity less than 100 uS/cm), precipitation water, and natural water, which have been filtered and acidified. With Zeeman background correction and a 20-uL sample, the method is applicable in the range from 0.2 to 5.0 ug/L. The analytical range and detection limits can be increased or decreased by varying the volume of sample injected or by diluting the sample. Purification of reagents and use of ASTM Type I reagent water (Method D1193)(American Society for Testing and Materials, 1991) is essential for obtaining low detection limits. |
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Applicable Concentration Range
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0.2-5.0 |
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Interferences
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Interferences in low ionic-strength samples, such as precipitation, normally are low. In addition, the use of the graphite platform reduces the effects of many interferences. Do not use matrix modifier with palladium; it may have elevated levels of silver which will cause high blank absorbencies. Precipitation samples usually contain small (<5 ug/L) concentrations of silver. Special precautionary measures need to be used during both sample collection and laboratory determination to prevent contamination. |
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Quality Control Requirements
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Quality-control samples area analyzed at a minimum of one in every ten samples. These QC samples include at least one of each of the following: blanks, quality control samples, third party check solutions, replicates, and spikes. Correlation coefficients for calibration curves must be at least 0.99. QC samples must fall within 1.5 standard deviations of the mean value. If all of the data-acceptance criteria in the SOPs are met, then the analytical data are acceptable. |
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Sample Handling
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Maximum Holding Time
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Relative Cost
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Sample Preparation Methods
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