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3A - Thermal Irradiation - INAA

A 30 g aliquot, if available, 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 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. Selected duplicates are analyzed when enough material is submitted.  

 

Code 3A (Heavy Mineral Concentrates) Elements and Detection Limits (ppm)

Element

Detection Limit

Upper Limit

Element

Detection Limit

Upper Limit

Element

Detection Limit

Upper Limit

Ag

5

10,000

Hf

1

5000

Sc

0.1

1000

As

2

100,000

Hg

5

-

Se

20

-

Au

5 ppb

30,000 ppb

Ir

50 ppb

-

Sm

0.1

10,000

Ba

200

-

La

1

10,000

Sr

0.2%

-

Br

5

10,000

Lu

0.05

1000

Ta

1

10,000

Ca

1%

50%

Mo

20

10,000

Tb

2

-

Ce

3

10,000

Na

0.05%

-

Th

0.5

10,000

Co

5

10,000

Nd

10

10,000

U

0.5

10,000

Cr

10

100,000

Ni

200

10,000

W

4

10,000

Cs

2

-

Rb

50

-

Yb

0.2

1000

Eu

0.2

2000

Sb

0.2

10,000

Zn

200

100,000

Fe

0.02%

75%

 

Reference :
Hoffman, E.L., 1992. Instrumental Neutron Activation in Geoanalysis. Journal of Geochemical Exploration, volume 44, pp. 297-319.


Activation Laboratories Ltd. | 41 Bittern Street, Ancaster, Ontario, L9G 4V5, Canada | TF: +1.888.228.5227
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