Sodium neutron activation

Analyses of alloys or ores for hafnium by plasma emission atomic absorption spectroscopy, optical emission spectroscopy (qv), mass spectrometry (qv), x-ray spectroscopy (see X-ray technology), and neutron activation are possible without prior separation of hafnium (19). Alternatively, the combined hafnium and zirconium content can be separated from the sample by fusing the sample with sodium hydroxide, separating silica if present, and precipitating with mandelic acid from a dilute hydrochloric acid solution (20). The precipitate is ignited to oxide which is analy2ed by x-ray or emission spectroscopy to determine the relative proportion of each oxide. 

For the deterrnination of trace amounts of bismuth, atomic absorption spectrometry is probably the most sensitive method. A procedure involving the generation of bismuthine by the use of sodium borohydride followed by flameless atomic absorption spectrometry has been described (6). The sensitivity of this method is given as 10 pg/0.0044M, where M is an absorbance unit the precision is 6.7% for 25 pg of bismuth. The low neutron cross section of bismuth virtually rules out any deterrnination of bismuth based on neutron absorption or neutron activation. 

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. 

To date, a few methods have been proposed for direct determination of trace iodide in seawater. The first involved the use of neutron activation analysis (NAA) [86], where iodide in seawater was concentrated by strongly basic anion-exchange column, eluted by sodium nitrate, and precipitated as palladium iodide. The second involved the use of automated electrochemical procedures [90] iodide was electrochemically oxidised to iodine and was concentrated on a carbon wool electrode. After removal of interference ions, the iodine was eluted with ascorbic acid and was determined by a polished Ag3SI electrode. The third method involved the use of cathodic stripping square wave voltammetry [92] (See Sect. 2.16.3). Iodine reacts with mercury in a one-electron process, and the sensitivity is increased remarkably by the addition of Triton X. The three methods have detection limits of 0.7 (250 ml seawater), 0.1 (50 ml), and 0.02 pg/l (10 ml), respectively, and could be applied to almost all the samples. However, NAA is not generally employed. The second electrochemical method uses an automated system but is a special apparatus just for determination of iodide. The first and third methods are time-consuming. 

Murthy and Ryan [823] used colloid flotation as a means of preconcentration prior to neutron activation analysis for arsenic, molybdenum, uranium, and vanadium. Hydrous iron (III) oxide is floated in the presence of sodium decyl sulfate with small nitrogen bubbles from 1 litre of seawater at pH 5.7. Recoveries of arsenic, molybdenum, and vanadium were better than 95%, whilst that of uranium was about 75%. 

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. 

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 ... 

Randle and Hartman [12] used thermal neutron activation in analysis to investigate total bromine in humic compounds in soil. Bromine was extracted from the soil water with sodium hydroxide or sodium pyrophosphate, then the extract dried prior to analysis. 

Flame Photometry, Atomic Absorption, and Neutron Activation. Comparatively few substances amenable to measurement by these techniques are used therapeutically chief among those that are being sodium, potassium, lithium, calcium, magnesium, zinc, copper, and iron, for all of which one or other of the techniques is the method of choice. 

Selenium is converted to its volatile hydride by reaction with sodium boro-hydride, and the cold hydride vapor is introduced to flame AA for analysis. Alternatively, selenium is digested with nitric acid and 30% H2O2, diluted and analyzed by furnace-AA spectrophotometer. The metal also may be analyzed by ICP-AES or ICP/MS. The wavelengths most suitable for its measurements are 196.0 nm for flame- or furnace-AA and 196.03 nm for ICP-AES. Selenium also may be measured by neutron activation analysis and x-ray fluorescence. 

Moreover the energies of these ( -partides (electrons) are known to be 1.39 MeV and that of the gamma-rays 1.38 MeV so that the measnned values of these magnitudes are characteristic of substances containing sodium. (Measurement of the y-radiadon is the usual procedure.) At least 70 of the elements can be activated in this way, by the capture of thermal neutrons, i.e.. by neutron activation analysis. An activation analysis follows a procedure similar to that shown ill Fig. 2. In almost all analyses, the sample materials are not treated before the bombardment, but are placed directly into the bombardment capsule or container. The length of the bombardment interval is usually determined by the half-life of the radionuclide used for the element of interest and the flux of nuclear particles. 

Olehy DA, Schmitt RA, Bethard WF. 1966. Neutron activation analysis of magnesium, calcium, strontium, barium, manganese, cobalt, copper, zinc, sodium, and potassium in human erythrocytes and plasma. J Nucl Med 6 917-927. 

NOTE All values are given as weight percent ( 95% confidence limit). Sulfate and chloride were analyzed by ion chromatography carbonate was analyzed by classical titration and calcium, magnesium, chlorine, aluminum, and sodium were analyzed by neutron activation analysis. 

Neutron Activation Analysis. Magnesium-26 has a small cross section of 0.03 b. The product of irradiation with thermal neutrons is Mg (1 9.5m). As shown in Table 1, several elements commonly present in biological materials give rise to radioactive nuclides with radiations at energy levels close to those characteristic of Mg. Neutron activation was used in the first trials of Mg as an in vivo tracer when measurements were made with a well-type Nal-Tl crystal detector (14,21). Under these conditions the presence of sodium, altuninum and manganese in the samples interfered in the accurate detection of Mg, but could be reduced or eliminated by sample purification. 

Mass spectrometry of zinc Isotopes has been realized using either chelates on a solids probe(10,11,17) or thermal Ionization of purified solutions(12). Both of these approaches require a chemical separation of all of the metals and this separation must be accomplished In an environment free of contamination from the metal(s) of Interest In the part-per blllion range (19). Neutron activation also requires a set of separation steps. In this case the requirement for a contamination-free environment Is the same but the chemical separation Is mainly to remove sodium and chlorine (2). 

Stoltman and Mainfort discussed some of the problems with NAA and most chemical composition studies of pottery. Neutron activation does not identify the minerals in the pottery it identifies only the chemical elements, and those elements that can occur in many different types of parent rock. Pottery is a human artifact whose chemicals derive from at least five sources (1) the clay (2) any added material such as temper (3) the water used to moisten the clay, which may contain such soluble elements as sodium, potassium, calcium, magnesium, or iron (4) any substance stored, cooked, or transported in the pot and (5) diagenesis, the absorption of chemicals from the soil in which the sherds have lain buried for millennia. Because it identifies minerals, ceramic petrography can link the sherd to the bedrock geology from which the temper came NAA, by contrast, cannot distinguish among the five sources that contributed the elements recorded. 

N2 = nitrogen NAA = neutron activation analysis NaOH = sodium hydroxide NH4OH = ammonium hydroxide... 

The first stratospheric aerosol chemical analyses showed that only a small quantity of the aerosol particles in the lower stratosphere could be of meteoritic origin (e.g. no nickel was found in the samples, see Table 24). This problem was studied in detail by Shedlovsky and Paisly (1966) who found by means of neutron activation of aerosol particles collected on filters that the stratospheric Fe/Na ratio is close to that reported for the Earth s crust. They concluded that less than 10 % of the iron and sodium identified at altitudes of 19-21 km come from meteorites. However, it is possible that between 30 and 50 km, where no such measurements were made, the meteoritic fraction of the aerosol is much more significant. 

Radiometric techniques, among the most sensitive analytical techniques, are very well known in clinical analysis and diagnosis. For sodium assay a neutron activation analysis (NAA)319 is proposed in the place of a spectro-metric method. This reduces the uncertainty value considerably because of the high selectivity and sensitivity of NAA. 

Batch leach experiments were performed on tailings material to determine the nature of contaminants distributed on sand and silt and clay-sized fractions. For the batch leach experiments, a mixture of tailings material was prepared using a chemical dispersant (sodium hexametaphosphate (NaPO ) ). The mixture was shaken and allowed to settle in covered beakers for sufficient time such that no particles with a diameter > 50 /im remained in suspension. The fines, which remained in suspension, represented the silt and clay-sized fraction of the samples. At the end of the settling period, the liquid was decanted from the beaker. The remaining sand-sized tailings were dried and transferred to a sealed vial. The decanted solution was passed through a 0.45 /im membrane filter, previously washed with distilled water, and the filtrate was collected and placed in a sealed container. The solids were dried and transferred to a sealed vial. The samples were then analyzed by instrumental neutron activation analysis. 

A reasonably complete analysis of the inorganic chemical composition of the aerosol requires much effort and involves, in addition to wet chemical methods, instrumental techniques such as neutron activation analysis, atomic absorption spectroscopy, or proton-induced X-ray emission (PIXE). These latter techniques yield the elemental composition. They furnish no direct information on the chemical compounds involved, although auxiliary data from mineralogy, chemical equilibria, etc. usually leave little doubt about the chemical form in which the elements occur. Thus, sulfur is present predominantly as sulfate, and chlorine and bromine as Cl- and Br-, respectively, whereas sodium potassium, magnesium, and calcium show up as... 

A non-destructive and rapid (6—8 min) determination of phosphorus and sodium in organophosphorus compounds may be achieved by fast neutron activation. A rapid method of determining P and P in aqueous solution utilizes a combination of Cerenkov radiation counting and liquid scintillation counting. Adsorption on charcoal before scintillation counting of P has also been used. ... 

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