Nuclear analytical techniques neutron activation analysis

Neutron activation analysis (NAA) is a supreme technique for elemental analysis (Section 8.6.1). Other nuclear analytical techniques, such as PIXE (Section 8.4.2) and RBS, also find application in investigations of diffusion processes [445]. 

The y particle is emitted virtually instantaneously on the capture of the neutron, and is known as a prompt y - it can be used analytically, in a technique known as prompt gamma neutron activation analysis (PGNAA), but only if such y s can be measured in the reactor during irradiation. Under the conditions normally used it would be lost within the nuclear reactor. In this reaction, no other prompt particle is emitted. The isotope of sodium formed (24Na) is radioactively unstable, decaying by beta emission to the element magnesium (the product nucleus in Figure 2.13), as follows ... 

It is obvious, therefore, that 14 MeV neutron activation analysis can not compete with thermal neutron activation analysis as a technique for trace element analysis. In simple matrices, however, the rapid and non-destructive nature of the technique recommends its use for routine analysis of large numbers of samples for elemental abundances at the one milligram level, or above. It is unfortunate that the element carbon can not be determined by this technique. The nuclear reaction 12C(n, 2n)1 C which would be of great analytical importance is endoergic to the extent of nearly 19 MeV. This reaction is obviously not energetically possible using the 14.7 MeV neutrons produced by the 2H(3H,w)4He reaction commonly employed in most neutron generators. 

Neutron activation analysis is an analytical technique for determining the elements present in a material as well as the amount of each element in the sample. The technique is based on a well-known reaction from nuclear chemistry. When an element is bombarded with neutrons, some of the atoms of that element may capture neutrons and incorporate them into their nuclei. Those atoms that do so have the same atomic number (that is, are the same element) as the original target element, but... 

Analytical techniques used for clinical trace metal analysis include photometry, atomic absorption spectrophotometry (AAS), inductively coupled plasma optical emission (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS). Other techniques, such as neutron activation analysis (NAA) and x-ray fluorescence (XRF), and electrochemical methods, such as anodic stripping voltammetry (ASV), are used less commonly For example. NAA requires a nuclear irradiation facility and is not readily available and ASV requires completely mineralized solutions for analysis, which is a time-consuming process. 

Neutron activation analysis is one of a small number of methods capable of multi-elemental analysis of subnanogram quantities of contaminants in semiconductors and other materials. Milligram to gram-sized samples of silicon, quartz, graphite, or organic materials are nearly Ideal for the method. The physics of the processes involved is simple, and qualitative identification of components is an Integral part of the quantitative analysis. Except for the need for access to a nuclear reactor, the equipment required is readily available commercially, and is comparable in cost and complexity to that used in other advanced analytical techniques. 

Some examples of applications of nuclear activation analytical techniques to elemental determinations in a variety of materials are presented in Table 2.10. The specific contents of some of these and other publications may be briefly highlighted. Cunningham and Stroube Jr. (1987) provide a nice coverage of the application of an instrumental neutron activation analysis procedure to analysis of food, describing the capabilities of INAA for the multielement analysis of foods as carried out for many years, and also currently, by analysts of the US Food and Drug Administration stationed at the NIST Nuclear reactor facility. Salbu and Steinnes (1992) touch upon applications of nuclear analytical techniques in environmental research, and Norman and Iyengar... 

Filby RH (1995) Isotopic and nuclear analytical techniques in biological systems a critical study. Part IX. Neutron activation analysis (technical report). Pure Appl Chem 67 1929-1941. 

Keywords Nuclear analytical techniques Atmospheric trace elements Instrumental neutron activation analysis Proton induced X-ray emission Biomonitoring... 

Neutron activation analysis and other nuclear analytical techniques... 

These include the use of the beta emitter ti/2 = 432 yr) in smoke detectors, the sterilization of food using nuclear radiation, the use of gamma sources to estimate the thickness of metal pipes, and the use of radioisotopes in an analytical technique called neutron activation analysis (see Box 21.1). 

Other analytical techniques have less frequently been used nuclear magnetic resonance spectroscopy (NMR) (e.g., tocopherols in toothpaste by hyphenated LC-NMR), energy dispersive X-ray fluorescence (ED-XRF) (e.g., heavy metals determination), surface enhanced Raman scattering (e.g., determination of 4-aminobenzoic acid or PABA, in sunscreens), neutron activation analysis (e.g., determination of iron and zinc), and thermometric analysis (e.g., fluoride in toothpaste). 

A variety of techniques based on different physical principles have been used for trace element measurements. The most commonly used include neutron activation analysis (NAA) [1], atomic absorption spectrometry [2,3], and mass spectrometry [4-7]. The two distinct advantages primarily responsible for the selection of NAA in earlier studies appeared to be the option to determine several trace elements simultaneously and the elimination of complex chemical separation steps. The poor precision values obtained by NAA have recently necessitated prechemical separation, which introduces problems of analyte loss, contamination, and blank correction. However, the major drawbacks are the requirement of a nuclear reactor facility, the slow turnaround of the samples, and the relatively high cost of analysis. Nonetheless, NAA is a well-established, multielemental, nondestructive technique with detection limits for most elements in the 1-50 p.g/liter range. This topic is covered by Heydom in Chap. 13 of this book. 

The analytical performance of ICP-MS is compared with other analytical techniques for the determination of trace metal oxide particulates after the simulated detonation of an RDD [10]. Table 20.9 shows a comparison of the instrumental parameters used in inductively coupled plasma optical emission spectroscopy (ICP-OES) and an ICP-MS instrument. These two techniques were used to analyze Sr, Ti, and Ce in ceramic oxides that may be used in RDDs. ICP-MS provided lower detection limits for the metals than ICP-OES. Overall method performance was comparable with ICP-OES and instrumental neutron activation analysis (INAA), another well-established nuclear and radiological analytical technique. 

The uranium content in soil can be determined directly by some analytical methods that are mainly based on nuclear techniques (variations of neutron activation analysis, gamma spectrometry, x-ray fluorescence, or laser-ablation ICPMS), but the common, popular, and more accurate methods require digestion and dissolution of the entire soil sample or at least rely on leaching the uranium out of the sample matrix. In principle, the methods used for assaying uranium in minerals (see Chapter 2) are also suitable for soil characterization, but uranium is usually present in the latter only as a low-level impurity, usually below 100 pg U g. We shall first overview the procedures deployed for the treatment of soil samples prior to analysis and refer to the analytical devices used for the measuranent of the uranium content and isotopic composition in these studies. 

Figure 1.13 Selected analytical techniques used for metallomics studies. ICP-OES, inductively coupled plasma optical emission spectroscopy, ICP-MS, inductively coupled plasma mass spectrometry LA-ICP-MS, laser ablation ICP-MS XRF, X-ray fluorescence spectroscopy PIXE, proton induced X-ray emission NAA, neutron activation analysis SIMS, secondary ion mass spectroscopy GE, gel electrophoresis LC, liquid chromatography GC, gas chromatography MS, mass spectrometry, which includes MALDI-TOF-MS, matrix-assisted laser desorption/ ionization time of flight mass spectrometry and ESI-MS, electron spray ionization mass spectrometry NMR, nuclear magnetic resonance PX, protein crystallography XAS, X-ray absorption spectroscopy NS, neutron scattering.

Neutron activation analysis (NAA) is a sensitive analytical technique useful for performing both qualitative and quantitative multielement analysis of major, minor, and trace elements in samples from almost every conceivable field of scientific or technical interest. NAA was discovered in 1936 by Hevesy and Levi. They found that Dy in samples became radioactive when bombarded by neutrons. From this observation, they quickly recognized the potential of employing nuclear reactions for the determination of elements present in different samples. Neutron activation analysis was soon established as a method of qualitative and quantitative element analysis. 

The information on the chemical speciation of trace elements in biological systems is much needed to evaluate their biological significance. Although a number of analytical techniques based on atomic behavior are available for the analysis of chemical speciation of trace elements, neutron activation analysis, as a nuclear analytical technique, can be successfully used in chemical speciation studies, after appropriate fractionation steps. Table 2.5 lists some typical applications of NAA in chemical speciation analysis of metalloproteins. The main advantages of NAA are of its high sensitivity and the absence of matrix effects inherited from the conventional neutron activation analysis. It can, therefore, be used to analyze the chemical species of trace elements in very small samples or complicated matrices, which is often impossible for non-nuclear techniques. 

Analysis of a metallodrug in a biological tissue is a challenging task in analytical chemistry, primarily because the traditional methods used are usually indirect and semi-quantitative to a large extent, and are unable to visualize the metal ions in vivo. Advanced nuclear analytical techniques, such as X-ray fluorescence, neutron activation analysis. X-ray emission. X-ray absorption near-edge structure spectroscopy, nuclear magnetic resonance, and isotope tracing/dilution techniques offer some means by which elemental distribution, oxidation states, and species structural information can be studied. ... 

The progress in metallomics and metalloproteomics is critically dependent on advances in methods for in silico (bioinformatics), in vitro and in vivo analysis bringing information on the identity, concentration, and localisation of elements and their species. Nuclear analytical techniques are a basic instrumental toolbox enabling and facilitating the acquisition of the relevant analytical information. They include, in the broader sense, not only neutron activation. 

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