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U.S. Geological Survey Open-File Report 2004-1350

Table 2.2 - Method for ultratrace elemental analyses

A 0.5 g sample is digested in aqua regia at 90C in a microprocessor controlled digestion box for 2 hours. The solution is diluted and analyzed by ICP/MS using a Perkin Elmer SCIEX ELAN 6100. International certified reference materials USGS GXR-1, GXR-2, GXR-4 and GXR-6 are analyzed at the beginning and end of each batch of samples. Internal control standards are analyzed every 10 samples and a duplicate is run for every 10 samples.

Code Ultratrace-1 Elements and Detection Limits (ppm)
Element Detection Limit Upper Limit
Au* 0.2 ppb 20,000 ppb
Ag* 0.05 200
Cu 0.1 10,000
Cd 0.1 200
Mn* 1 10,000
Mo 0.01 1,000
Pb* 0.01 1,000
Ni* 0.1 5,000
Zn* 0.1 10,000
As* 0.1 10,000
B* 1 5,000
Ba* 0.5 6,000
Sb 0.02 500
W* 0.2 200
Al* 0.01% 10%
Be* 0.1 1,000
Bi 0.02 2,000
Ca* 0.01% 50%
Ce* 0.01 200
Co 0.1 500
Cr* 0.5 500
Cs* 0.1 100
Eu* 0.1 100
Fe* 0.01% 50%
Ga* 0.02 500
Ge* 0.1 500
Hf* 0.1 500
In 0.02 100
K* 0.01% 5
La* 0.5 200
Li 0.5 1,000
Lu* 0.1 100
Mg* 0.01% 10%
Na* 0.001% 1%
Nb* 0.1 500
Nd* 0.1 200
Rb* 0.1 500
Re 0.001 100
Se 0.1 1,000
Sm* 0.1 100
Sn* 0.05 200
Sr* 0.5 1,000
Ta* 0.05 50
Tb* 0.1 100
Te 0.02 500
Th* 0.1 200
Tl* 0.02 500
U* 0.1 200
V* 1 1,000
Y* 0.1 500
Yb* 0.1 200
Zr* 0.1 5,000

0.5 g of sample is digested with aqua regia (0.5 ml H20, 0.6 ml concentrated HNO3 and 1.8 ml concentrated HCl) for 2 hours at 95C. Sample is cooled then diluted to 10 ml with deionized water and homogenized. The samples are then analyzed using a Perkin Elmer OPTIMA 3000 Radial ICP for the 37 element suite. A matrix standard and blank are run every 13 samples.

A series of USGS-geochemical standards are used as controls. This digestion is near total for base metals however will only be partial for silicates and oxides.

Code 1E2 Elements and Detection Limits (ppm)
Element Detection Limit Upper Limit
Ag* 0.1 100
Al* 0.01%  
As* 3  
B* 5  
Ba* 1  
Be* 1  
Bi* 2  
Ca* 0.01%  
Cd 0.2 2,000
Co* 1  
Cr* 2  
Cu 1 10,000
Fe* 0.01%  
Hg 1  
K* 0.01%  
La* 1  
Mg* 0.01%  
Mn* 1 10,000
Mo* 2 10,000
Na* 0.001%  
Ni* 1 10,000
P* 0.001%  
Pb* 2 5,000
S* 0.001% 20%
Sb* 5  
Sc* 0.1  
Sn* 5  
Sr* 1  
Te* 1  
Ti* 0.01%  
Tl* 2  
V* 1  
W* 1  
Y* 1  
Zn* 1 10,000
Zr* 1  
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