Neutron activation advantages

One of the important advantages of NAA is its applicability to almost all elements in the periodic table. Another advantage of neutron activation is that it is nondestructive. Consequently, NAA is an important technique for analyzing archaeological and forensic samples, as well as works of art. 

Radiochemical methods of analysis take advantage of the decay of radioactive isotopes. A direct measurement of the rate at which a radioactive isotope decays may be used to determine its concentration in a sample. For analytes that are not naturally radioactive, neutron activation often can be used to induce radioactivity. Isotope dilution, in which a radioactively labeled form of an analyte is spiked into the sample, can be used as an internal standard for quantitative work. 

Instiximental neutron activation analysis (INAA) is considered the most informative and highly sensitive. Being applied, it allows detecting and determination of 30-40 elements with the sensitivity of 10 -10 g/g in one sample. The evident advantage of INAA is the ability to analyze samples of different nature (filters, soils, plants, biological tests, etc.) without any complex schemes of preliminai y prepai ation. 

Atomic absorption spectroscopy of VPD solutions (VPD-AAS) and instrumental neutron activation analysis (INAA) offer similar detection limits for metallic impurities with silicon substrates. The main advantage of TXRF, compared to VPD-AAS, is its multielement capability AAS is a sequential technique that requires a specific lamp to detect each element. Furthermore, the problem of blank values is of little importance with TXRF because no handling of the analytical solution is involved. On the other hand, adequately sensitive detection of sodium is possible only by using VPD-AAS. INAA is basically a bulk analysis technique, while TXRF is sensitive only to the surface. In addition, TXRF is fast, with an typical analysis time of 1000 s turn-around times for INAA are on the order of weeks. Gallium arsenide surfaces can be analyzed neither by AAS nor by INAA. 

Table 8.72 Main features of neutron activation analysis Advantages...

The extreme sensitivity of neutron activation analysis can be both an advantage and disadvantage. The obvious advantage is that one can obtain data on small and precious... 

Neutron activation is a highly sensitive technique which has special, almost unique advantages for trace analysis (3, 22). If the original sample can be irradiated without prior chemical treatment and with a... 

We are using a plastic scintillator in our spectrometer. This has the advantage not to get neutron activated, to be a good neutron thermalizer and to yield fast timing signals. It is also relatively cheap. An inorganic scintillator would certainly also perform satisfactorily. 

Neutron activation analysis (NAA) technique has also been used for determining low levels of barium in human blood (Olehy et al. 1966). This technique is based on the interaction of the nuclei of individual barium atoms with neutron irradiation, resulting in the emission of x-rays (photons). Detection limits of 7 pg barium/L of erythrocyte and 66 pg barium/L of plasma were obtained (Olehy et al. 1966). The advantages of the NAA technique are its nondestructive nature of sample and minimum sample manipulation. Disadvantages of this technique include its high costs and a nuclear reactor may not be readily available to many laboratories. 

In PIGE the y-emission is usually prompt. If very low amounts of trace elements have to be detected it can be advantageous to use a delayed decay. In this case, the technique is called charged particle activation (CPA) and is an analogue to neutron activation analysis (NAA). It has the advantage that the prompt background from interfering reactions is completely removed as irradiation and analysis are completely separated in time. This also allows to remove external contaminants in the short time between irradiation and measurement which further improves detection limits. A comprehensive description of the technique can be found in the ion beam analysis handbook [2], For 19F CPA is conceivable in special cases via the 19F(d,dn)18F reaction. However, we have found only one application in the literature [64],... 

Despite the availability of neutron activation, X-ray fluorescence and spectrographic multielement methods, atomic absorption continues to be very important. It has advantages of versatility and ease of calibration for laboratories with single element or variable analytical requirements. The high capital cost of the equipment makes the other methods competitive only for multielement, multisample programs. 

In both total and sequential dissolutions, the result is a solution containing the components of rocks and soils. This solution is then analyzed by different methods. Mostly, spectroscopic methods are used atomic absorption and emission spectroscopic methods, ultraviolet, atom fluorescence, and x-ray fluorescence spectrometry. Multielement methods (e.g., inductively coupled plasma optical emission spectroscopy) obviously have some advantages. Moreover, elec-troanalytical methods, ion-selective electrodes, and neutron activation analysis can also be applied. Spectroscopic methods can also be combined with mass spectrometry. 

Because neutron activation analysis of zinc appeared to require little sample preparation and Is capable of better precision than GC/MS, It was the method of analysis selected for our first experiment. Separation of zinc from other minerals In the samples was required, however, eliminating this as an advantage of NAA. Precision of this method was not as good In our experiment as had been expected. 

EUTRON ACTIVATION ANALYSIS IS A VERY SENSITIVE TECHNIQUE for trace element determinations in various samples. If there are no elements that mutually interfere, the purely instrumental version of this method is often chosen for its established advantages such as accuracy, speed, sensitivity, simultaneous multielement determination, and sample preservation (1). For these reasons, instrumental neutron activation analysis (INAA) was applied to samples taken from a series of metal-working residues excavated at Tel Dan, Israel, from 1985 to 1986. 

The present method of analysis offers several distinct advantages. The first of these is speed calcium, barium, and strontium concentrations are determined simultaneously in a short irradiation, and analysis of up to seven samples can be completed within hours. Neutron activation analysis is highly sensitive to the elements of interest compared with other methods such as x-ray fluorescence and atomic absorption techniques. Additionally, the required sample size is small (10-20 mg), thus resulting in little alteration of archaeological specimens. 

Neutron Activation Analysis This technique permits the quantitative and qualitative identification of elements. It is based on the conversion of a stable atomic nucleus into a radioactive nucleus by bombarding it with neutrons. The radiation emitted by the radioactive nuclei is then measured [154]. The advantages of NAA include [16, 154] ... 

Nondestructive method (EMAA instrumental neutron activation analysis) based on the measurement of radioactivity of samples analyzed by high-resolution gamma spectrometry using the differentials of the rate of decay of the radionuclides analyzed in time [15]. NAA has several important advantages [15] ... 

Activation analysis may be applied in many variants. Neutron activation analysis (NAA) is the most widely used, but often charged particle activation or photon activation are more advantageous. If the energy of the projectiles can be varied, many variations are possible. The application of the manifold methods of activation depends on the availability of research reactors and accelerators. In addition, purely instrumental or radiochemical methods may be used. In instrumental activation analysis, the samples are measured after irradiation without chemical separation, whereas radiochemical activation analysis includes chemical separation. 

Radiochemical group separation has a major advantage over individual element separation in that it is far less time consuming, yet it can permit suflBcient separation to allow precise analysis. For example, by simply separating the rare earth elements (REE) as a group after neutron activation, it is possible to measure most of the rare earth spectra by direct counting and thus determine their distribution. 

In activation analysis, as in all trace element determinations, care must be exercised to avoid contamination. One of the advantages of activation analysis is that the manipulation prior to irradiation of the sample is minimized. Contamination by inactive material after irradiation is unimportant, provided it does not take place in amounts sufficient to affect the chemical yield. The restrictions imposed on neutron activation by selfshielding mentioned above may necessitate the use of small samples and either liquid or solid dilutions of the pure standard material to overcome the difficulty. 

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