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2A - Humus - INAA

Ground humus samples weighing 6 to 15 g are compressed under 30 tons of pressure to form a briquette (smaller samples are weighed in vials).  Briquettes are stacked with flux wires and an internal standard (1 for 29 samples) and irradiated at a thermal flux of 7 x 10 12 ncm-2 s-1 for 15 minutes. After a 7-day period, to allow Na-24 to decay, the samples are counted on a high purity Ge detector with a 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. Between 10 and 30 % of the samples are rechecked by re-measurement. For values exceeding the upper limits, assays are recommended. One standard is analyzed for every 29 samples. Duplicates are analyzed when provided.

Required Preparation:  Code  B1 (drying and blending humus)

   

Code 2A (Humus) Elements and Detection Limits (ppm)

Element

Detection Limit

Element

Detection Limit

Element

Detection Limit

Element

Detection Limit

Ag

2

Cs

0.5

Na

100

Sr

100

As

1

Eu

0.2

Nd

3

Ta

0.5

Au

1 ppb

Fe

0.05%

Ni

10

Tb

0.2

Ba

100

Hf

0.5

Rb

20

Th

0.5

Br

1

Hg

0.5

Sb

0.1

U

0.1

Ca

0.5%

Ir

5 ppb

Sc

0.1

W

1

Ce

1

La

0.1

Se

2

Yb

0.1

Co

1

Lu

0.1

Sm

0.1

Zn

20

Cr

1

Mo

0.5

 

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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