Because of the high costs involved in INAA as well as the need of a reactor, it would be a good idea for someone who starts an INAA project to make first a sample set to be analysed by Petrography. After that, EDXRF could be applied in to establish whether the results obtained by thin-section analyses will hold water. After that, one need INAA in order to get quantitative data to be placed in a database and then compared with existing INAA databases after one knows whether the data producing labs are compatible, i.e. after inter-calibration..
INAA is excellent and sophisticated technique for quantitative analysis of elemental concentration. This technique don't required sample preparation (dissolution), which is routinely done with other analytical techniques(ICP-OES, ICP-MS), and results obtained from INAA are comparative with these techniques. Recently, k0-INAA is introduced as standerless technique, which don't required sample matching matrix standard.
In term of cost it's expensive and time consuming and related to availability of research reactor, which i think don't have with many research institute around the world.
I have a question for Nadeem: "What do you mean with "Standerless technique" in your answer?
Secondly, in a general sense, neutron activation (without the word 'instrumental') included chemical analyses performed on a sample before starting the analysis.. Instrumental neutron activation means that no chemical separation is necessary, so that the elemental composition is measured directly on all the elements..
There are different method for obtaining the quantitative data using INAA
a) Absolute Method b) Relative or comparison method c) k0-INAA
For absolute method no standard or the reference material is used along with sample and conc. of element is easily calculated using simple equation, but there is uncertainty associated with this method due to some parameter.
Relative method requires comparison of unknown sample with know sample of same matrix. The uncertainty associated with this method is less compared to absolute method, but generally it is difficult to find or to prepare such a standard with certified composition and several standards have to be used for calculating concentration of element in sample
While the application of semi-absolute, standardless k0-INAA and requires the determination of thermal to epithermal neutron flux ratio (f) and epithermal neutron flux shape factor (alpha) which characterize the irradiation position. The (f) and (alpha) were determined by Al–0.1 % Au wire (IRMM-530RC, EU, Geel) and ZrO2powder (99.99 %, Aldrich). The conc. of element in the sample is determined by conventional activation analysis formula containing a " k0-factor' a compound nuclear constant.
RNAA although requires the separation of few element with in a sample, which create some interference with other element and difficult of analyzed. Other than this no requirement of sample preparation.
I thought that the original question was: What is the future of neutron activation. As When it comes to environmental studies, INAA has also proven to be sufficient. So, again, as long as there are nuclear reactors, there will be a great opportunity to continue with applying INAA to archaeometry material culture.
The difference between the various ways NAA or INAA is used is of lesser importance also because it was not part of the original question. Success to all of you. Iwrite earlier, INAA has still a great future because there remain many provenance questions to be answered and as long as it will be applied to ceramics and obsidian, the outcome will be satisfactory as it has been since the first archaeological question was answered at Berkeley in 1967. For metals, there are other techniques and here INAA is not enough.
In terms of cost, NAA has been made expensive by the limited number of nuclear research reactors available for use worldwide. However, with the availability of those eactors, NAA will continue to be the best analytical technique applied in many fields like nuclear industry, archeology, geology, materials science, soil science, medicine as well as the environmental management. This is because NAA offers a lot of advantages compared to other techniques. Besides being multi-elemental and its high sensitivity, NAA offers the non-destructive option as well as the choice of isotopes. Another exceptional advantage provided by NAA is that samples can be liquids, solids or even powders. I have recently learnt about Compton Scattering Neutron Activation Analysis (CSNAA) which is used to reduce spectra background and thus lowering the detection limits. NAA's future really looks promising.
Zina Ndlovu , How CSNAA reduce the spectra background ? would you like to elaborate?
Nadeem, CSNAA mainly involves the following:
1. The use of an additional detector for observing Compton scattered gamma-rays and then the suppression of the Compton continuum generated by high-energy gamma-rays.
2. The reduction of the background of the measurement by suppression of the natural background by means of passive mad active shielding of the main detector from natural radioactivity presented in the environment surrounding the system and
cosmic radiation.
To read more about this, I'ld like to refer you to the article below;
"COMPTON SUPPRESSION NEUTRON ACTIVATION ANALYSIS:
PAST, PRESENT AND FUTURE." by S. LANDSBERGER, and S. PESHEV
I hope you'll find it useful.
A small historical note regarding Compton Scattering Neutron Activation Analysis.
How are pseudo elemental pulses inhibited that derive from the Compton effect?
Well, during my sabbaticals at LBNL, Berkeley-California in 1989 and 1996 , I have be present to see the development of an instrument inhibiting the simultaneous emission of iridium (Ir 192) present in samples taken from the K-T Boundary in order to prove the impact of a large asteroid, an event that took place in the Gulf of Mexico, 65 million years ago.
The background known as the Compton effect could be taken care of by measuring the Ir emissions with two gamma ray detectors simultaneously (hence coincidences), in which system both detectors would be placed into a third detector surrounding the two detectors.
The idea came from Louis Alvarez who together with Frank Asaro commanded that such a machine should be built (in 1983). Three years later, 1987-1989, the machine worked and in 1996 it was named the Luis W. Alvarez Iridium Coincidence Spectrometer which at present is able to analyze with great precision 19 more elements.
P.S. If my memory is still OK, the detectors were hung op in mineral oil to filter out the environmental background. About the latter, I admit, am not so sure.
P.S.2 Are we talking about the same set-up as the by Zina mentioned CSNAA?
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