USGS Test Method I-2725


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Source:
USGS

Method Name:
Silver, atomic absorption spectrophotometry, graphite furnace, LIS. Official Name: Determination of low-level silver by graphite furnace atomic absorption spectrophotometry

Description:
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 HGA or THGA instruments; the only differences are listed in sections 4.1.2 and 5.3.

Scope:
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.

Citation:
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

Interferences:
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 (

QC Requirements:
Calibrate instrument using calibration standards (CAL); quality control samples (QCS); and laboratory blanks (LB) analyzed at a minimum of 1 for every 10 samples.

Maximum Holding Time:
180 days

Media:
WATER

Subcategory:
Inorganic

Concentration:
0.2-5.0 micrograms per liter

Precision:
-

Detection:
MDL determined according to 40 CFR 136 Appendix B.

Revision Number:
May-91

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Analytical testing dots