Detection by neutron activation

The metal can be analyzed by several instruments including flame-AA, ICP-AES, ICP-MS, and x-ray fluorescence. Also, it can be detected by neutron activation analysis. 

B22. Budinger, T. F., Forwell, J. R., Smith, A. R., and Bicknel, M., Human tissue trace element detection by neutron activation without chemical separation. Int. J. Appl. Radial. Isotop. 23, 49-56 (1972). 

Example 15.1 What is the minimum mass of gold that can be detected by neutron activation analysis under the conditions listed below ... 

Elements can be analyzed with high detection power that cannot be detected by neutron activation, e.g., light elements (deuterium, beryllium, carbon, nitrogen, oxygen, fluorine, silicon, phosphorus) or elements of environmental interest (nickel, thallium, lead, bismuth). 

Holzbecker and Ryan [825] determined these elements in seawater by neutron activation analysis after coprecipitation with lead phosphate. Lead phosphate gives no intense activities on irradiation, so it is a suitable matrix for trace metal determinations by neutron activation analysis. Precipitation of lead phosphate also brings down quantitatively the insoluble phosphates of silver (I), cadmium (II), chromium (III), copper (II), manganese (II), thorium (IV), uranium (VI), and zirconium (IV). Detection limits for each of these are given, and thorium and uranium determinations are described in detail. Gamma activity from 204Pb makes a useful internal standard to correct for geometry differences between samples, which for the lowest detection limits are counted close to the detector. 

Until it was known that the half-life of Tc is much shorter than 10 years Herr looked for technetiimi-98 in a munber of minerals from Norway and South Africa by neutron activation analysis. This most sensitive method was also used by Alperovitch et al. and Anders et al. to detect this isotope in nature. According to the nuclear reaction... 

Trace amounts of Tc are also determined in filter paper and vegetable samples by neutron activation analysis The procedure consists of the following major steps separation of technetium from the sample, thermal neutron irradiation of the Tc fraction to produce °°Tc, post-irradiation separation and purification of °°Tc from other activated nuclides, and counting of the 16 s Tc in a low-background P counter. The estimated detection limits for Tc in this procedure are 5 x 10 g in filter paper and 9 x 10 g in vegetable samples. 

Selected ion monitoring can be used for the determination of the relative amount of each component of a mixture, introduced into the mass spectrometer by the direct inlet probe However, such a determination requires reference mixtures of known composition for calibration. In the present experiment, since the monochloro pentaziridino derivative had not yet been isolated in the pure form, it was necessary to determine its concentration, by an auxiliary method, in a sample which could then be utilized as a reference mixture for further experiments. In order to do this we titrated chlorine in the toxic sample of MYKO 63 (B) by the classical method. The results indicated that the amount of N3P3AZJCI was between 0.5-1.5 %. The large statistical error is due to the low chlorine content in the sample examined. Thus, we used the remarkable possibilities provided by neutron activation analysis when the impurity to be quantified is a chlorinated moiety. It is well-known indeed that the C1 -f 2n peak is amongst the most easily detectable by neutron... 

The mass spectrum of SOAz is shown Fig. 38 and its pattern is quite different from that of MYKO 63 in fact we no longer observe the fall of the Az leaves which characterizes any mass spectrum within the MYKO 63 series. The base peak is at m/z 320 and there are very few other secondary peaks till m/z 50. No chlorinated impurity could be detected either by mass spectrometry or by neutron activation. 

The determination of 129I in low-level radioactive waste was accomplished by radioactive instrumental neutron activation analysis [3]. A different group reported the determination of both 129I and 127I by neutron activation analysis and inductively coupled plasma mass spectrometry [4]. The method was very rapid - a sample could be analysed in three minutes. However, interference from 129Xe resulted in limited sensitivity for 129I detection. 

Many different separation and detection systems have been used for speciation. For example, size fractionation and ultra-filtration have been used for separation with the separated species then being determined by neutron activation (Tanizaki et al., 1992). These physico-chemical separation processes are, however, time consuming and the species have to be collected and then determined separately. Although the techniques are invaluable for certain types of speciation where the interaction of the species with colloids and sediments is important, hybrid or coupled techniques are usually preferred. 

R. R. Ruch, V. P. Guinn, and R. H. Pinker, Detection of Gunpowder Residues by Neutron Activation Analysis, Nuclear Science and Engineering 20 (1964) 381. 

Selenium forms a volatile derivative, piazselenol, which can be subjected to GC analysis (Scheme 5.39). Young and Christian [612] treated selenium with 2,3-diaminonaph-thalene at pH 2.0 and extracted the resulting piazselenol into -hexane. With the use of an ECD, down to 5 10-I° g of selenium could be detected. The procedure, applied to the analysis of selenium in human blood, urine and river water, led to results equivalent to those obtained by neutron activation analysis. Similarly, Nakashima and Toei [613] performed the reaction of selenium (as selenious acid) with 4-chloro-o-phenylenediamine at pH 1 and extracted the derivative into toluene. They reported a detection limit of 0.04 jug. Shimoishi [614] analysed the content of selenium in metallic tellurium by this method. The sample was dissolved in aqua regia, followed by reaction with 4-nitro-o-phenylenediamine and extraction into toluene. Down to 10 ng of selenium could be determined using only a few milligrams of sample. Common ions did not interfere even when present in a large excess. Selenium in marine water was determined after the same derivatization step [615],... 

Islam, M.T., Islam, S.A., Latif, S.A. Detection of arsenic in water, herbal and soil samples by neutron activation analysis technique. Bull. Environ. Contam. Toxicol. 79, 327-330 (2007)... 

Table 17.2. Detection limits by neutron activation analysis at a thermal neutron flux density of cm on the assumption that 10 Bq allow quantitative determination.

Background Caused by Filters. Since all of the particles were collected on membrane filters it was necessary to determine the blank metal concentrations in the filter. This enabled an estimation of how many particles must be collected in order that the levels of the metals were significantly greater than the blank filter. For this study, both neutron and flame atomic absorption spectrometric analyses were used and the results are shown in Table I. The analyses by neutron activation were made on the filter directly whereas those by atomic absorption spectrometry were obtained by extracting the filter with nitric acid (16M Ultrex). There are apparent differences between the two sizes of membrane filters which are probably related to the fact that these filter sets were obtained at different times. Also, while the metal blanks within a particular batch of filters vary by negligible amoimts, the variations between batches are considerable. These determinations are near the detection limits for both techniques, and therefore there are considerable uncertainties associated with the results. However, these blanks did indicate the minimum level of metals which must be collected if the analyses are to be significant. 

Other Metal-Peptide and -Protein Interactions.—The determination of protein-bound trace elements in biological material by neutron activation analysis has been described Zn, Hg, Cu, and Se were accurately detected in human liver samples, provided that most of the element concerned was protein bound. An interaction of mercury with a protein or a protein-DNA complex has been invoked to explain the partitioning of the metal in euchromatin over heterochromatin (from mouse liver nuclei) by a 10 1 ratio. " Bovine retinas, isolated rod outer segments and emul-phogene extracts of rod outer segments have been shown to contain appreciable amounts of Zn ", Ca and the zinc levels being light sensitive. 

Silicon consists predominantly of Si (92.23%) together with 4.67% Si and 3.10% Si. No other isotopes are stable. The Si isotope (like the proton) has a nuclear spin I =, and is being increasingly used in nmr spectroscopy. Si, formed by neutron irradiation of Si, has ti 2.62 h it can be detected by its characteristic activity ( max 1-48 MeV) and is very useful for the quantitative analysis of Si by neutron activation. The radioisotope with the longest half-life ( 172 y) is the soft emitter Si ( max... 

Recently, the determination of Tc in mixed fission products by neutron activation was reported. " TcOj was separated from the bulk of fission products and other elements in dissolved nuclear fuel by an iron(IIl)-oxidc-hydrate precipitation. 1 he filtrate containing TcOj was loaded on an anion exchange resin and I c bonded on the resin was exposed to a neutron flux in a nuclear reactor for only one minute. The counting of the 539 keV y-rays of ° Tc was performed with a germanium detector and a multichannel analyzer. The minimum detectability was 0.3 pg Tc limited by resin impurities and capsule materials [27]. 

Neutron detection by foil activation is based on the creation of a radioisotope by neutron capture, and subsequent counting of the radiation emitted by that radioisotope. Foil activation is important not only for neutron flux measurements but also for neutron activation analysis, which is the subject of Chap. 15. This section presents the basic equations involved. 

The Choice of Tracer and Its Chemical Form. As stated previously, the tracer should be easy to detect, inexpensive, nontoxic at environmentally useful concentrations, have low environmental abundance, and, most important, exhibit similar behavior to the material being traced. Among the elements used for their ease of detection (in the absence of other elements) by neutron activation analysis are Sc, V, Mn, Cu, As, Br, Y, Pd, In, Sb, I, the rare earths, Ta, W, Re, Ir, Au, and U. In particular matrix, some of these may become much more di Scult to detect. For example, in marine samples, the high levels of 15-h Na produced by activation may necessitate pre- (or post-) irradiation removal of the Na or use of trace elements with long half-lives (t > 5 days). 

A second advantage, already mentioned, is that NAA is applicable to small samples. Also, it is by nature multielement, although the analytical sensitivity of each element (lower limit of detection) depends on nuclear quantities such as the reactor neutron flux, the capture cross-section, the branching ratio and energy of the particular characteristic gamma or X-ray observed and the half-life of the radioisotope. Thus the sensitivity can vary markedly across the Periodic Table. However, for purposes of provenience research, the multielement character is all-important, as will be seen in Section 2.4 below. It is usually possible by the mere inspection of a table of analytical data to say that the data was or was not obtained by neutron activation, because of the bias toward certain elements. 

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