Comparative Neutron Activation Analysis

In comparative activation analysis, an analysed standard is irradiated with thermalised neutrons under identical conditions to those of the sample to be analysed and they are counted after activation under the same conditions. The mass of element X to be determined is calculated from the relation  

The standard should be as close as possible to the sample in composition, consistency etc. to minimise self shielding i.e. attenuation of the neutron flux in a target during irradiation, and the self absorption of p particles during counting. 

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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. 

Calcium-selective electrodes have long been in use for the estimation of calcium concentrations - early applications included their use in complexometric titrations, especially of calcium in the presence of magnesium (42). Subsequently they have found use in a variety of systems, particularly for determining stability constants. Examples include determinations for ligands such as chloride, nitrate, acetate, and malonate (mal) (43), several diazacrown ethers (44,45), and methyl aldofuranosides (46). Other applications have included the estimation of Ca2+ levels in blood plasma (47) and in human hair (where the results compared satisfactorily with those from neutron activation analysis) (48). Ion-selective electrodes based on carboxylic polyether ionophores are mentioned in Section IV.B below. Though calcium-selective electrodes are convenient they are not particularly sensitive, and have slow response times. 

Lieser et al. [628] studied the application of neutron activation analysis to the determination of trace elements in seawater, with particular reference to the limits of detection and reproducibility obtained for different elements when comparing various preliminary concentration techniques such as adsorption on charcoal, cellulose, and quartz, and complexing agents such as dithizone and sodium diethyldithiocarbamate. 

Nixon277 compared atomic absorption spectroscopy, flame photometry, mass spectroscopy, and neutron activation analysis as methods for the determination of some 21 trace elements (<100 ppm) in hard dental tissue and dental plaque silver, aluminum, arsenic, gold, barium, chromium, copper, fluoride, iron, lithium, manganese, molybdenum, nickel, lead, rubidium, antimony, selenium, tin, strontium, vanadium, and zinc. Brunelle 278) also described procedures for the determination of about 20 elements in soil using a combination of atomic absorption spectroscopy and neutron activation analysis. 

Neutron activation analysis is an attractive method in many trace element problems, or where the total amount of sample is limited. Many geochemical studies of trace constituents and semi-conductor developments have used the technique, whilst in recent years pollution investigations have provided a new focus. In forensic science small flakes of paint, single hairs and a variety of other small samples have been analysed and identified by activation analysis. In recent years activation analysis has lost further ground to ICP-MS which provides more comprehensive information and is more readily operated. Sensitivity is also comparable in many cases. 

Tsolakidou, A. and Kilikoglou, V. (2002). Comparative analysis of ancient ceramics by neutron activation analysis, inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and X-ray fluorescence. Analytical and... 

In the first step, we were able to separate this penta derivative by preparative H.P.L.C. and we subsequently treated it with an excess of propyleneimine in order to reach the required hexasubstituted compound. Under such conditions, we succeeded in preparing a N3P3(MeAz)g real sample (free of chlorine, as demonstrated by neutron activation analysis) identified by mass spectrometry (Fig. 32) and by P nmr (Fig. 33) (6 = — 36 ppm with 85 % HjPO as standard, to be compared with 8(N3P3Azg) = --37 ppm). The refractive index of this sample, n = 1.4825, appeared to be significantly far from Ratz s value. 

Sheppard 1980). The level of thorium measured in 1969 in East Chicago, IN, a heavily polluted industrial area, was 1.3 ng/m compared to a value of 0.27 ng/m at a rural location in Michigan (Niles, Ml) (Dams et al. 1970). The air particulate samples collected from 250 sites in the United States by the National Air Surveillance Network (NASN) of ERA during 1975 and 1976 were analyzed for thorium-232 by neutron activation analysis. The measured concentrations at 250 urban and nonurban sites in the United States ranged from 0.2-1.0 ng/m, with a mean concentration of 0.3 ng/m (Lambert and Wilshire 1979). The mean concentrations of thorium-228, thorium-230 and thorium-232 in New York City air (sample collected on the roof above the 14th floor) were 36 aCi/m (aCi = 10 Ci), 36 aCi/m, and 37 aCi/m, respectively (Wrenn et al. 1981). 

In this report we describe our quantitative analyses for three major components and for 16 trace elements present from parts per billion (ppb) to parts per million (ppm) in Sasanian silver by thermal neutron activation analysis. The analytical data are discussed element by element. Some of the conclusions which can be drawn from the objects are discussed. Since the amount of comparative data available is too small for generalizations, many of our conclusions and assumptions are subject to change when more data and information become available. 

It seemed to us that the whole problem of Olmec trade and the interrelationship of the preclassic sites in Mesoamerica offered an unusually favorable case for the method of grouping via paste-compositional patterns based on neutron activation analysis. As a start on this program we include here the analysis of six preclassic Tlatilco figurines, and we compare their analyses with those of two modern specimens and touch upon the archaeological conclusions possible. 

In most obsidian provenance studies, the ability to employ compositional differences to discriminate between sources depends, to a certain extent, on the number of elements measured. Because instrumental neutron activation analysis (INAA) is capable of measuring 25-30 elements in obsidian with excellent precision, numerous combinations of trace and major elements are available for comparing differences between sources. The main requirements for success are that all sources have been located and analyzed, and that the internal variation measured within the sources be smaller than the compositional differences measured between the sources (23). 

The following section focuses on the variability of the clay bodies or pastes of the glazed ceramics previously characterized by LA-ICP-MS and LA-TOF-ICP-MS. The purpose of this study is to compare the variation in the ceramic pastes with the different glaze decorative technologies through time. The variability in the ceramic pastes will be characterized through instrumental neutron activation analysis (INAA) and petrographic analysis. 

Since the mid-1960s, a variety of analytical chemistry techniques have been used to characterize obsidian sources and artifacts for provenance research (4, 32-36). The most common of these methods include optical emission spectroscopy (OES), atomic absorption spectroscopy (AAS), particle-induced X-ray emission spectroscopy (PIXE), inductively coupled plasma-mass spectrometry (ICP-MS), laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), X-ray fluorescence spectroscopy (XRF), and neutron activation analysis (NAA). When selecting a method of analysis for obsidian, one must consider accuracy, precision, cost, promptness of results, existence of comparative data, and availability. Most of the above-mentioned techniques are capable of determining a number of elements, but some of the methods are more labor-intensive, more destructive, and less precise than others. The two methods with the longest and most successful histoty of success for obsidian provenance research are XRF and NAA. 

With few exceptions, the results given by fluorometry, chromatography and neutron activation analysis compare well with those obtained by inductively coupled plasma atomic emission spectrometry. The precisions obtained for the various samples were very good for between- and within-batch samples. 

Earlier methods for the determination of uranium in soils employed spectrophotometry of the chromophore produced with arsenic(III) at 655 nm [237 ] and neutron activation analysis [238]. More recently, laser fluorescence [239] and in situ laser ablation-inductively coupled plasma atomic emission spectrometry [240] have been employed to determine uranium in soil. D Silva et al. [241] compared the use of hydrogen chloride gas for the remote dissolution of uranium in soil with microwave digestion. 

Hoffmann and Lieser [112] used XFS to determine a range of elements in leaves and grass and compared this technique with neutron activation analysis, AAS, ICP-atomic emission spectrometry, polarography and voltammetry. 

Schlesinger et al ( 3) reported that non-destructive neutron activation analysis (NAA) can be employed to compare drugs sold in illicit channels through the determination of their elemental compositions. This early work was amplified by Pro and Brunelle (4), combining atomic absorption analysis with NAA. Although the determination of elemental composition can be useful, this approach suffers from the fact that it may not be used when heroin has been packaged differently or adulterated with another... 

There are many examples of relatively straightforward use of ICP-MS for the analysis of biological fluids. Antimony has been measured in blood after a 14 1 dilution [236]. Cesium serum levels were found to be elevated in patients with alcohol dementia but not in Alzheimer s disease patients [237]. Cobalt levels in rat serum depended on the form of cobalt [238] ingested. Bismuth levels were measured in human blood and urine by using a direct injection nebulizer [239]. Lead was measured in the blood and blood plasma of smelter workers and the general population [240]. The measurement of trace elements in serum by ICP-MS has been compared to results from neutron activation analysis and proton-induced x-ray emission [241]. Semiquantitative analysis can also be used to obtain a rapid screening of samples [242]. 

The fact that neutron irradiation of hydrogen and carbon produces no significant radioactivity makes Neutron Activation Analysis (NAA) a very sensitive analytical technique for detecting impurities in polymer cable insulation and has been extensively used for this purpose. It is therefore of some interest to compare PIXE with NAA. 

Silver evaporations were done in the same preparation chamber using an inhouse-constructed evaporation assembly containing a resistively heated tungsten basket. Ag coverages were controlled by a quartz crystal thickness monitor. The deposition rates were typically 0.01 to 0.1 A/s depending on the desired coverage. Coverages were subsequently calibrated by XPS analysis of the Ag 3d and polymer core level (C Is and O Is) intensities as compared to known standards, and by neutron activation analysis (111. 

Methods of stable Isotope analysis. Three methods of a-nalysls have been used for analysis of stable Isotopes of minerals neutron activation analysis (NAA) (10), gas-chromato-graph-mass spectrometry (GC/MS) (11), and thermal Ionization mass spectrometry (TI/MS) ( 6). The maximum attainable precision of each of these analytical methods Is compared In Table III (2). 

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