INAA
Samples analyzed by Instrumental Neutron Activation Analysis (INAA) are encapsulated and irradiated in a nuclear reactor. After a suitable decay, samples are measured for the emitted gamma ray fingerprint.
Major mineral applications by INAA include rocks, soils, sediments (both stream and lake bottom) humus, vegetation and heavy minerals. The INAA technique allows for multiple elements to be determined simultaneously and a small sample size can be used. A major advantage of INAA analysis is the fact that the sample does not have to be put into solution, particularly beneficial for some geological matrices where complete dissolution is difficult to effect. This method is quite sensitive, accurate and precise, and is used to analyze for minor and select trace elements in low concentrations. INAA is very good for Au, Co, As, Sb, W, Ta, U, Th, Cs, In, Re, Cl and lower levels of most LREE.
The cost for this type of analysis is comparable to other single element analytical techniques for Au and is quite cost effective when determining a full suite of elements. Refractory elements are very difficult to put into solution easily and even elements such as Au can be extremely difficult to put into solution completely where INAA is a major advantage
INAA (Instrumental Neutron Activation Analysis) is an analytical technique dependent on measuring gamma radiation induced in the sample by irradiation with neutrons. The primary source of neutrons for irradiation is usually a nuclear reactor. Each activated element emits a “fingerprint” of gamma radiation which can be measured and quantified. Routine multi-element analyses by INAA are performed on practically any material from the smallest sample which can be weighed accurately to very large samples.
A 30g aliquot, if available, is encapsulated in a polyethylene vial and irradiated along with flux wires at a thermal neutron flux of 7 x 10 12 ncm-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 and control standards, the decay-corrected activities are compared to a calibration developed from multiple certified international reference materials. 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 sample material is available.
1D (Au+34) Elements and Detection Limits (ppm)
Element | Detection Limit | Upper Limit |
---|---|---|
Ag | 5 | 100,000 |
As | 2 | 10,000 |
Au | 5 ppb | 30,000 ppb |
Ba | 100 | 500,000 |
Br | 1 | 1,000 |
Ca | 1% | 50% |
Ce | 3 | 10,000 |
Co | 5 | 5,000 |
Cr | 10 | 100,000 |
Cs | 2 | 10,000 |
Eu | 0.2 | 2,000 |
Fe | 0.02% | 75% |
Element | Detection Limit | Upper Limit |
---|---|---|
Hf | 1 | 500 |
Hg | 1 | 1,000 |
Ir | 5 ppb | 10,000 ppb |
La | 1 | 10,000 |
Lu | 0.05 | 1,000 |
Mo | 5 | 10,000 |
Na | 0.05% | 10% |
Nd | 5 | 10,000 |
Ni | 50 | 10,000 |
Rb | 30 | 10,000 |
Sb | 0.2 | 10,000 |
Sc | 0.1 | 200 |
Element | Detection Limit | Upper Limit |
---|---|---|
Se | 5 | 10,000 |
Sm | 0.1 | 10,000 |
Sn | 0.05% | 10% |
Sr | 0.1% | 40% |
Ta | 1 | 10,000 |
Tb | 0.5 | 1,000 |
Th | 0.5 | 10,000 |
U | 0.5 | 10,000 |
W | 4 | 10,000 |
Yb | 0.2 | 1,000 |
Zn | 50 | 100,000 |
1D Enhanced (Au+34) Elements and Detection Limits (ppm)
Element | Detection Limit | Upper Limit |
---|---|---|
Ag | 5 | 100,000 |
As | 0.5 | 10,000 |
Au | 2 ppb | 30,000 ppb |
Ba | 50 | 500,000 |
Br | 0.5 | 1,000 |
Ca | 1% | 50% |
Ce | 3 | 10,000 |
Co | 1 | 5,000 |
Cr | 5 | 100,000 |
Cs | 1 | 10,000 |
Eu | 0.2 | 2,000 |
Fe | 0.01% | 75% |
Element | Detection Limit | Upper Limit |
---|---|---|
Hf | 1 | 500 |
Hg | 1 | 1,000 |
Ir | 5 ppb | 10,000 ppb |
La | 0.5 | 10,000 |
Lu | 0.05 | 1,000 |
Mo | 1 | 10,000 |
Na | 0.01% | 10% |
Nd | 5 | 10,000 |
Ni | 20 | 10,000 |
Rb | 15 | 10,000 |
Sb | 0.1 | 10,000 |
Sc | 0.1 | 200 |
Element | Detection Limit | Upper Limit |
---|---|---|
Se | 3 | 10,000 |
Sm | 0.1 | 10,000 |
Sn | 0.02% | 10% |
Sr | 0.05% | 40% |
Ta | 0.5 | 10,000 |
Tb | 0.5 | 1000 |
Th | 0.2 | 10,000 |
U | 0.5 | 10,000 |
W | 1 | 10,000 |
Yb | 0.2 | 1,000 |
Zn | 50 | 100,000 |
Reference:
Hoffman, E.L., 1992. Instrumental Neutron Activation in Geoanalysis. Journal of Geochemical Exploration, volume 44, pp. 297-319.
One standard is run for every 11 samples. One blank is analyzed per work order. Duplicates are analyzed when samples are provided.
Code 5A Basic Elements and Detection Limits (ppm)
Element | Detection Limit | Upper Limit |
---|---|---|
As | 2 | 10,000 |
Au | 5 ppb | 30,000 ppb |
Ba | 200 | 100,000 |
Br | 2 | 1000 |
Ce | 5 | 10,000 |
Co | 2 | 10,000 |
Cr | 10 | 100,000 |
Cs | 2 | 10,000 |
Eu | 0.2 | 2000 |
Element | Detection Limit | Upper Limit |
---|---|---|
Fe | 0.02% | 75% |
Hf | 1 | 5000 |
La | 1 | 10,000 |
Lu | 0.1 | 1000 |
Mo | 5 | 10,000 |
Na | 500 | 100,000 |
Nd | 10 | 10,000 |
Rb | 50 | 10,000 |
Sb | 0.2 | 10,000 |
Element | Detection Limit | Upper Limit |
---|---|---|
Sc | 0.5 | 200 |
Se | 5 | 10,000 |
Sm | 0.1 | 10,000 |
Ta | 2 | 10,000 |
Th | 1 | 10,000 |
U | 2 | 10,000 |
W | 5 | 10,000 |
Yb | 0.5 | 1000 |
Code 5B Other Elements and Detection Limits (ppm)
Element | Detection Limit | Upper Limit |
---|---|---|
As | 1 | 10,000 |
Au | 5 ppb | 30,000 ppb |
Ba | 100 | 100,000 |
Br | 0.5 | 1000 |
Ce | 3 | 10,000 |
Co | 0.5 | 10,000 |
Cr | 1 | 100,000 |
Cs | 0.5 | 10,000 |
Eu | 0.2 | 2000 |
Element | Detection Limit | Upper Limit |
---|---|---|
Fe | 0.01% | 75% |
Hf | 0.5 | 500 |
La | 0.1 | 10,000 |
Lu | 0.05 | 1000 |
Mo | 2 | 10,000 |
Na | 100 | 100,000 |
Nd | 5 | 10,000 |
Rb | 20 | 10,000 |
Sb | 0.1 | 10,000 |
Element | Detection Limit | Upper Limit |
---|---|---|
Sc | 0.1 | 200 |
Se | 2 | 10,000 |
Sm | 0.01 | 10,000 |
Ta | 0.5 | 10,000 |
Th | 0.2 | 10,000 |
U | 0.1 | 10,000 |
W | 2 | 10,000 |
Yb | 0.2 | 1000 |
Reference:
Hoffman, E.L., 1992. Instrumental Neutron Activation in Geoanalysis. Journal of Geochemical Exploration, volume 44, pp. 297-319.
Elements and Detection Limits (ppm)
Element | Detection Limit | Upper Limit |
---|---|---|
Al | 1 | 100,000 |
Br | 5 | 10,000 |
Cl | 100 | 100,000 |
Cu | 5 | 2,500 |
Dy | 0.5 | 5,000 |
Ga | 5 | 10,000 |
I | 0.5 | 5,000 |
In | 0.1 | 5,000 |
Mg | 0.05% | 50% |
Mn | 0.1 | 10,000 |
Na | 50 | 200,000 |
Re | 1 | 5,000 |
Ti | 50 | 100,000 |
V | 0.1 | 10,000 |
Reference:
Hoffman, E.L., 1992. Instrumental Neutron Activation in Geoanalysis. Journal of Geochemical Exploration, volume 44, pp. 297-319.