Neutron Activation Analysis for Life Sciences

Frank Laboratory of Neutron Physics

The Sector of Neutron Activation Analysis and Applied Research Summer practice in JINR Dubna 06-23.09.2016

Supervised by: Prof. M.V Frontasyeva and Dr. W. Badawy

Participants Josiel de Jesús Barrios Cossio, Cuba

Dimitrijević Aleksandra, Serbia

Dmitrović Svetlana, Serbia

Zdolsek Nikola, Serbia

Alexander Naa’ilah, South Africa

Biyela Talente, South Africa

Yende Nomcebo Fikile, South Africa

Mdunjana Ntandokazi, South Africa

Kobese Nokubonga, South Africa

Neutron Activation Analysis (NAA) • NAA is a method for determination of elements based on

conversion stable nuclei to other, mostly radioactive nuclei via nuclear reactions and measurements of reaction products [Bode, 1996]

• NAA was discovered in 1936 by G. Hevesy (Hungary) and H. Levi (Denmark)

Fundamentals of NAA

Relative Standardization

Absolute method

- Requires precise knowledge of (E)

- Accurate measurement of (E) and

- It requires standards to have all the elements

- The error mainly depends on ms and Anc

m = Anc e- te,s ms

Anc,s e- te

Absolute Standardization

Applications

Advantages

• Wide possibilities of applications

• Non destructive analysis

• Multi-element analysis

• Sensitivity to parts-per-billion for specific elements

• Customizable analysis

Limitations

• Need for nuclear reactor

• Work with radioactive materials

• Time of analysis

• Sample preference

Comparison between NAA and other techniques

• Atomic Absorption Spectrometry (AAS)

The study of absorption spectra by means of passing electromagnetic radiation through an atomic medium that is selectively absorbing; this produces pure electronic transitions free from vibrational and rotational transitions

• X-Ray Fluorescence Analysis (XFA)

X-ray Fluorescence (XRF) analysis is a widely used method of elemental analysis providing both qualitative and quantitative compositional information.This analysis is widely used for elemental analysis and chemical analysis, particularly in the investigation of metals, glass, ceramics and building materials, and for research in geochemistry, forensic science and archaeology.

• Synchrotron radiation

Synchrotron radiation is the name given to the radiation which occurs when charged particles are accelerated in a curved path or orbit. Classically, any charged particle which moves in a curved path or is accelerated in a straight-line path will emit electromagnetic radiation.

The disadvantages of using this methods above is that they are expensive, difficult to calibrate and other factors like sample characteristic, availability and accuracy and precise.

While INAA is relatively low on the prices when we compare it to these techniques

IBR – 2 Reactor in JINR

Parameters of IBR – 2:

- Average power 2 MW

- PuO2 fuel

-Rotation rate, rev/min: main reflector 600 auxiliary reflector 300

- Neutron density flux 1016

n·m-2

·s-1

Neutron energy distribution:

- Thermal 0.025 eV-0.5 eV

- Epithermal 0.5 eV – 100 keV

- Fast 0.1 MeV – 25 Me

Ch1-Ch4 –irradiation channels, S- intermediate storage, DCV- directional control valves, L- loading unit, RCB- radiochemical glove-cell, U- unloading unit, SU- separate unit, SM- storage magazine, R- repacking unit, D- detector, CB- control board, R1-R3- the rooms where the system is located.

Radioanalytical complex REGATA

Types of NAA

• Destructive

(radiochemical) – the resulting radioactive sample is chemically decomposed and the elements are chemically separated.

Non-destructive (instrumental) – sample is kept intact and the radionuclides are determined, taking advantage of the differences in decay rates via measurements at different decay intervals

Instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) is used to determine the concentration of trace and major elements in a variety of matrices. A sample is subjected to a neutron flux and radioactive nuclides are produced. As these radioactive nuclides decay, they emit gamma rays whose energies are characteristic for each nuclide.

Measurement of content of samples

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Sample preparation

Neutron irradiation of samples

Decay of radioactivity

Decay periods

Measurement of γ-ray spectra of samples and standards with HPGe-detector

Processing of the γ-ray spectra using GENIE 2000

Calculation of element content

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Sample preparation

Irradiation of Samples

• The principle involved in NAA, is the irradiation of a sample with a neutron source that produces specific radionuclides.

• Different sources of neutrons can be used: • Reactor (IBR-2)

• Fusors

• Isotope Sources

• Gas Discharge Tubes

• This results in characteristic gamma rays emitted by the decaying radionuclides. The gamma rays are quantitatively measured using gamma spectroscopy.

• Data analysis yields concentrations of major, minor, trace and rare earth elements.

Case Study (Joint project between JINR & SA)

• A joint study between University of the Western Cape (RSA) and Frank Laboratory for Neutron Physics (JINR).

• Dr Paul Eze, Dr Marina Frontasyeva and Prof. Leslie Petrik

• Elemental Composition of Fly Ash: A comparitive study using nuclear and related analytical techniques.

A minimum requirements

- Determine the position of peaks in the spectrum

- Estimate the areas of the peaks (together with uncertainties)

- Calculate the energy of the gamma-ray each peak represents

- Correct for counting losses due to dead time and random summing

-Make corrections for decay from a reference time

- Convert peak areas to activity or concentration, either by reference to an

efficiency function or by direct comparison with a reference spectrum

Processing of Gamma-Ray Spectra

In general, a full computer spectrum analysis will consist of three phases:

(1) set up data libraries for energy, peak width and efficiency

calibration and for sample analysis

(2) use spectra of reference sources to generate energy, width and

efficiency calibration data files

(3) analyse sample spectra by referring to those data libraries and

calibration files

Software systems: Genie 2000™ (Canberra) and GammaVision™ (ORTEC) -Allow complete calibration of energy, peak width and detector efficiency -Able to search through a spectrum seeking out statistically significant peaks, assigning them to nuclides, and calculating sample activity

GENIE 2000 - the program allows minimizing human involvement in routine long-term measurements of the spectra of the induced activity - simultaneous measurements are conducted

for visualization of information, the program automatically provides the file with areas of interest and displays them in the window of Genie-2000 -areas of interest are graphical peak intervals found by the program while spectra are being processed

results are stored in a file with the values of the activities of identified isotopes and the minimal detectable activity of these isotopes

calculation of elemental concentrations in the samples is performed by a relative method using the Concentration program - the values of the calculated concentrations of elements with uncertainties of calculations and minimal detectable concentrations for the given experimental conditions are stored in the NAA database

CASE STUDY

STUDY OF SPIDER SILK COMPOSITION BY NEUTRON ACTIVATION ANALYSIS

Native Spider Silk

• Remarkable mechanical properties

• Biocompatible

• Biodegradable

• Production of native ss on industrial level failed due to cannibalistic nature of spiders

• Recombinant DNA technology for production of SS proteins

Composition of spider silk

Core-shell structured fiber:

1) 2 main proteins-spindroins (Gly, Ala, Pro)

• Ala domains form β-sheat secondary structure

• Gly-Gly-Ala and Gly-Pro-Gly-X-X domains form 31 helices

2) ‘skin’

3) Glycoprotein coat

4) Lipid layer

The first NAA of spider silk

• Spider silk from Pholcus phalangoides spider

• Basement of one of the buildings in Vinča Institute of Nuclear Sciences

• Spider silk as a potential biomonitoring material

Element mg/kg %

Na 7110 3

Mg 9060 3

Al (P) 20100 2

Si 62600 34

S 6000 34

Cl 7720 7

K 10200 10

Ca 5.0 5

Sc 7.0 3

Ti 1680 11

V 93.2 6

Cr 966 4

Mn 559 5

Fe 38200 5

Ni 366 8

Co 194 6

Cu 507 30

Zn 15800 7

Se 10.9 8

As 55.8 5

Br 59.7 2

Rb 23.1 17

Sr 148 9

Zr 850 30

Nb 58.2 34

Element mg/kg %

Mo 58.8 31

Ag 6.17 18

Cd 1.43 10

Sb 40.5 4

I 376 14

Ba 741 5

Cs 3.2 3

La 24 4

Ce 144 4

Nd 29.6 24

Sm 5.62 31

Eu 2.94 30

Gd 2.75 9

Tb 0.584 4

Dy 3.7 30

Tm 0.022 30

Yb 4.64 31

Lu 1.4 68

Hf 23.7 8

Ta 5.41 2

W 260 30

Au 0.23 30

Hg 3.23 16

Th 4.91 2

U 8.77 3

Preliminary results

Perspectives

• Comparison of spider silk with the dust collected from the same place

• More detailed analysis of composition of spider silk

• Comparison in composition of fibers between the species

• Influence of diet on composition of fibers

• Using NAA to study the aforementioned research points as an analytical technique.

Conclusion

• Neutron Activation Analysis (NAA) is a useful method for the simultaneous determination of major, minor and trace elements of geological, environmental and biological samples in ppb-ppm range with or without chemical separation

Acknowledgments • Prof. Marina V. Frontasyeva

• Dr. Wael Badawy

• S.S. Pavlov

• Prof Octavian Duliu

• Nikita Sergeevich

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Thank you for your paying attention