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4E - Research - INAA, Total Digestion - ICP, Lithium Metaborate/Tetraborate Fusion - ICP

INAA Portion

A 1 g aliquot is encapsulated in a polyethylene vial and irradiated with flux wires and an internal standard (1 for 11 samples) at a thermal neutron flux of 7 x 1012 n cm-2 s-1. After a 7-day period, to allow Na-24 to decay, the samples are counted on a high purity Ge detector with resolution of better than 1.7 KeV for the 1332 KeV Co-60 photopeak. Using the flux wires, the decay-corrected activities are compared to a calibration developed from multiple certified international reference materials. The standard present is only a check on accuracy and is not used for calibration purposes. From 10-30% of the samples are rechecked by re-measurement. For values exceeding the upper limits, assays are recommended.

 

One standard is run for every 11 samples. One blank is analyzed per work order.  Duplicates are analyzed when samples are provided.

 

The method is described by Hoffman, E.L., 1992. Instrumental Neutron Activation in Geoanalysis.  Journal of Geochemical Exploration, volume 44, pp. 297-319.

 

Major Elements Portion

A 0.2 g sample is mixed with a mixture of lithium metaborate/lithium tetraborate and fused in a graphite crucible. The molten mixture is poured into a 5% nitric acid solution and shaken until dissolved (~ 30 minutes). The samples are run for major oxides and selected traces on a Varian Vista ICP. Calibration is achieved using a variety of international reference materials. Independent control standards are also analyzed. Results on the international standards run with the samples are appended at the end of the report.

 

Base Metals and Selected Trace Elements

A 0.25 g sample is digested with four acids beginning with hydrofluoric, followed by a mixture of nitric and perchloric acids, heated using precise programmer controlled heating in several ramping and holding cycles which takes the samples to dryness. After dryness is attained, samples are brought back into solution using hydrochloric acid. With this digestion certain phases may be only partially solubilized. These phases include zircon, monazite, sphene, gahnite, chromite, cassiterite, rutile and barite. Ag greater than 100 ppm and Pb greater than 5,000 ppm should be assayed as high levels may not be solubilized. Only sulphide sulfur will be solubilized.

 

An in-lab standard (traceable to certified reference materials) or certified reference materials are used for quality control.

 

Samples are analyzed using a Varian Vista ICP.

 

Code 4E-Research Fusion ICP

Oxide

Detection Limit

Al2O3

0.01%

CaO

0.01%

Fe2O3

0.01%

K2O

0.01%

MgO

0.01%

MnO

0.001%

Na2O

0.01%

P2O5

0.01%

SiO2

0.01%

TiO2

0.001%

Loss on Ignition

0.01%

 

Code 4E-Research Trace Elements and Detection Limits (ppm)

Element

Detection Limit

Upper Limit

Reported By

Element

Detection Limit

Upper Limit

Reported By

Ag

0.5

100,000

ICP/INAA

Nd

1

10,000

INAA

As

1

100,000

INAA

Ni

1

10,000

ICP

Au

1 ppb

30,000 ppb

INAA

Rb

10

10,000

INAA

Ba

1

30,000

ICP/INAA

S

0.001%

20%

ICP

Be

1

10,000

ICP

Sb

0.1

10,000

INAA

Bi

2

10,000

ICP

Sc

0.01

1000

INAA

Br

0.5

-

INAA

Se

0.5

10,000

INAA

Cd

0.5

5,000

ICP

Sm

0.01

10,000

INAA

Ce

1

10,000

INAA

Sr

2

-

ICP

Co

0.1

10,000

INAA

Ta

0.3

10,000

INAA

Cr

0.5

100,000

INAA

Tb

0.1

1000

INAA

Cs

0.2

INAA

Th

0.1

10,000

INAA

Cu

1

10,000

ICP

U

0.1

10,000

INAA

Eu

0.05

-

INAA

V

5

-

ICP

Hf

0.2

-

INAA

W

1

10,000

INAA

Hg

1

10,000

INAA

Y

1

10,000

ICP

Ir

2 ppb

10,000 ppb

INAA

Yb

0.05

-

INAA

La

0.05

10,000

INAA

Zn

2

10,000

ICP

Lu

0.01

1000

INAA

Zr

4

-

ICP

Mo

2

10,000

INAA

 

 

Typical ICP Analysis of some USGS and Canmet Standards (%)

Std.

SiO2

Al2O3

Fe2O3

MnO

MgO

CaO

Na2O

K2O

TiO2

P2O5

SY3

59.51

11.62

6.47

0.32

2.54

8.25

4.17

4.23

0.14

0.52

MRG1

39.43

8.59

17.93

0.17

13.74

14.77

0.73

0.18

3.78

0.07

DNC1

46.91

18.46

9.76

0.15

10.05

11.27

1.99

0.24

0.47

0.07

BIR1

47.78

15.43

11.52

0.17

9.70

13.75

1.86

0.02

0.95

0.02

W2

52.58

15.35

10.72

0.16

6.37

10.98

2.31

0.64

1.05

0.12

G2

68.72

14.95

2.65

0.03

0.71

1.87

4.08

4.48

0.48

0.13

STM1

59.64

18.07

5.24

0.22

0.07

1.09

8.87

4.24

0.13

0.1


 

Code 4E-Research options:

4E - XRF

4E - ICP-MS



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