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E4EE - 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 10 12 n cm -2 -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.

 

Total Digestion ICP Portion

A 0.25 g sample aliquot is digested with a mixture of HClO4, HNO3, HCl, and HF at 200 °C to fuming and is then diluted with aqua regia. This leach is partial for magnetite, chromite, barite and other spinels and potentially massive sulphides.

 

Major Elements by Fusion ICP-OES, Trace Elements by ICP-MS

Samples are prepared and analyzed in a batch system. Each batch contains a method reagent blank, certified reference material, and 17% replicates. Samples are mixed with a flux of lithium metaborate and lithium tetraborate and fused in an induction furnace. The molten melt is immediately poured into a solution of 5% nitric acid containing an internal standard, and mixed continuously until completely dissolved (~30 minutes). The samples are then run for major oxides and selected trace elements (Code 4B) on a combination simultaneous/sequential Thermo Jarrell-Ash ENVIRO II ICP.

 

For the ICP analysis, reagent blanks with and without the lithium borate flux are analyzed, as well as the method reagent blank.  Interference correction verification standards are analyzed.  Calibration is performed using multiple USGS and CANMET certified reference materials. Two of the standards are used during the analysis for every group of ten samples. This standard brackets the group of samples.  The sample solution is also spiked with internal standards and is further diluted and introduced into a Perkin Elmer SCIEX ELAN 6000 ICP/MS using a proprietary sample introduction methodology. Calibration is performed using USGS and CANMET certified reference materials.

 

Code E4EE Fusion ICP

Oxide

Detection Limit

Al2O3

0.01%

CaO

0.01%

Fe2O3

0.01%

K2O

0.01%

MgO

0.01%

MnO

0.01%

Na2O

0.01%

P2O5

0.01%

SiO2

0.01%

TiO2

0.005%

LOI

0.01%

 

Code E4EE  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

5

10,000

INAA

As

2

100,000

INAA

Ni

1

10,000

ICP

Au

5 ppb

30,000 ppb

INAA

Rb

20

10,000

INAA

Ba

3

30,000

ICP/INAA

S

0.001%

20%

ICP

Be

1

10,000

ICP

Sb

0.2

10,000

INAA

Bi

2

10,000

ICP

Sc

0.1

1000

INAA

Br

1

-

INAA

Se

3

10,000

INAA

Cd

0.5

5,000

ICP

Sm

0.1

10,000

INAA

Ce

3

10,000

INAA

Sr

2

-

ICP

Co

1

10,000

INAA

Ta

1

10,000

INAA

Cr

1

100,000

INAA

Tb

0.5

1000

INAA

Cs

0.5

INAA

Th

0.5

10,000

INAA

Cu

1

10,000

ICP

U

0.5

10,000

INAA

Eu

0.1

-

INAA

V

5

-

ICP

Hf

0.5

-

INAA

W

3

10,000

INAA

Hg

1

10,000

INAA

Y

1

10,000

ICP

Ir

2 ppb

10,000 ppb

INAA

Yb

0.1

-

INAA

La

0.5

10,000

INAA

Zn

2

10,000

ICP

Lu

0.05

1000

INAA

Zr

4

-

ICP

Mo

5

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 E4EE Options:

 

E4E-XRF

The trace elements analyses are done on pressed powder pellets made from 6 g of sample. Spectral interferences are corrected from pre-calculated interfering factors.  Because of the trace level (< 1,000 ppm) of the analytes, only the mass absorptions are corrected for matrix effects.  The mass absorption coefficients are derived from measuring the Compton scatter of the Rh-tube (e.g., Nisbet et al., 1979.  Fortschr. Miner., volume 57, pp. 264-279). The background and mass absorption corrected intensities are then calculated against the calibrations constructed from 24 international geological reference materials.  In general, the limits of detection are between 1 to 5 ppm.

 

Option E4E-XRF  Elements and Detection Limits (ppm)

Element

Detection Limit

Upper Limit

Ga

5

10,000

Nb

1

10,000

Pb

5

1,000

Rb

2

20,000

Sn

5

10,000




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