Instrumental neutron activation detection limits

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. 

With analytical methods such as x-ray fluorescence (XRF), proton-induced x-ray emission (PIXE), and instrumental neutron activation analysis (INAA), many metals can be simultaneously analyzed without destroying the sample matrix. Of these, XRF and PEXE have good sensitivity and are frequently used to analyze nickel in environmental samples containing low levels of nickel such as rain, snow, and air (Hansson et al. 1988 Landsberger et al. 1983 Schroeder et al. 1987 Wiersema et al. 1984). The Texas Air Control Board, which uses XRF in its network of air monitors, reported a mean minimum detectable value of 6 ng nickel/m (Wiersema et al. 1984). A detection limit of 30 ng/L was obtained using PIXE with a nonselective preconcentration step (Hansson et al. 1988). In these techniques, the sample (e.g., air particulates collected on a filter) is irradiated with a source of x-ray photons or protons. The excited atoms emit their own characteristic energy spectrum, which is detected with an x-ray detector and multichannel analyzer. INAA and neutron activation analysis (NAA) with prior nickel separation and concentration have poor sensitivity and are rarely used (Schroeder et al. 1987 Stoeppler 1984). 

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. 

X-ray fluorescence spectrometry (XRF) and instrumental neutron activation analysis (INAA) are commonly used for multi-element analysis of rock, soil, and sediment samples since they do not require chemical dissolution. However, the detection limit for arsenic using XRF is on the order of 5 mg kg and is too high for many environmental purposes. Once dissolved, arsenic can be determined using many of the methods described above... 

Table I. Detection Limits Measured at NBS for Trace Element Analysis of Si and Si02 by Instrumental Neutron Activation...

In instrument neutron activation analysis (INAA) a small fraction of the stable atomic nuclei present in the sample are made radioactive by irradiation with neutrons or other particles. By measuring the resulting radioactivity, the original elements present can be determined. Reactor or thermal neutrons are usually used. The method does not work well for certain key elements of environmental interest including silicon, sulfur, and lead. Table 6.2 shows INAA detection limits for various elements and typical concentrations of these elemenis in urban air. In atmospheric samples, the fiiiiii of detectability for a particular clement depends on the quantities of the other elements in the filter matrix. The table is based on a total air sample of 17 actually used in the measurements. The tabulated results show that all elements listed could be detected in this air volume with the exception... 

NAA has been used to determine selenium levels in environmental samples. Dams et al. (1970) reported a detection limit of lxlO 10 g/m3 selenium using nondestructive NAA for determining selenium in air particulate matter. For determining selenium levels in soil, radiochemical variants of NAA have been commonly employed (Bern 1981). Instrumental neutron activation analysis (INAA) is frequently used to determine selenium concentrations in water and can also be used to distinguish between selenium(IV) and selenium(VI) oxidation states (Bern 1981). INAA is also used to determine selenium concentrations in air (Bern 1981). 

Mantel M (1983) Limits of detection of trace dements in biological materials analysed by instrumental neutron activation analysis usingX-ray spectrometry and magnetic deflection of beta-rays. Analyst 108 1190-1194. 

Mercury concentrations in constructed and actual crude oil samples were measured using three analytical methods that were compared with respect to accuracy, precision, and detection limit. The combustion method (U.S. EPA 7473 hybrid) and a commercial extraction method (non-standard) were found adequate to provide a good combination of sensitivity and accuracy, while instrumental neutron activation analysis was found to suffer from interferences from elements other than mercury but typically in crude oil. In the combustion method, direct syringe injection of aliquots to the combustion chamber was found advantageous in that it minimized opportunities for loss of volatile mercury. 

LiBOi can be carried out in a platinum crucible at 1000°C. Acid digestion typically involves acid mixtures such as concentrated nitric and hydrochloric acid heated to temperatures of 100°C or more. The aim of the digestion in this case is to completely break down the matrix. Total tin analysis is routinely carried out using atomic absorption spectrometry (AAS) and inductively coupled plasma (ICP) coupled with atomic emission spectrometry (AES) or with mass spectrometry (MS). Hydride generation is commonly used to reduce detection limits. This technique involves the addition of a reductant such as sodium borohydride to form tin hydride. Hydride generation has been used commonly with ICP-AES, ICP-MS, and AAS. Other techniques employed for total tin determination are instrumental neutron activation and X-ray fluorescence spectrometry. 

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. 

Manganese in aqueous solution may be analyzed by several instrumental techniques including flame and furnace AA, ICP, ICP-MS, x-ray fluorescence and neutron activation. For atomic absorption and emission spectrometric determination the measurement may be done at the wavelengths 279.5, 257.61 or 294.92 nm respectively. The metal or its insoluble compounds must be digested with nitric acid alone or in combination with another acid. Soluble salts may be dissolved in water and the aqueous solution analyzed. X-ray methods may be applied for non-destructive determination of the metal. The detection limits in these methods are higher than those obtained by the AA or ICP methods. ICP-MS is the most sensitive technique. Several colorimetric methods also are known, but such measurements require that the manganese salts be aqueous. These methods are susceptible to interference. 

Neutron activation analysis (NAA) with a rapid radiochemical separation has been the method generally used in recent years, but requires substantial investment, has high operating cost and limited availability. Modem flameless atomic absorption (AAS) instruments provide sensitivity approaching that of NAA and offer a viable alternative for the detection of firearms discharge residue. 

Trace amounts of titanium can be determined by X-ray fluorescence spectrometry, neutron activation analysis (NAA), atomic absorption techniques (AAS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). In case of AAS, a high-temperature flame (nitrous oxide, acetylene) is essential, and the optimum wavelengths are 364.3 and 365.4 nm the sensitivity is low. With the graphite furnace, a lower detection limit of approximately 0.5 xg L can be achieved. ICP-OES is especially sensitive, and is the recommended instrumental... 

Detection limits are presented for 61 elements by ten analytical determinative methods FAAS flame atomic absorption spectrometry ETAAS electrothermal atomization atomic absorption spectrometry HGAAS hydride generation atomic absorption spectrometry including CVAAS cold vapor atomic absorption spectrometry for Hg ICPAES(PN) inductively coupled plasma atomic emission spectrometry utilizing a pneumatic nebulizer ICPAES(USN) inductively coupled plasma atomic emission spectrometry utilizing an ultrasonic nebulizer ICPMS inductively coupled plasma mass spectrometry Voltammetry TXRF total reflection X-ray fluorescence spectrometry INAA instrumental activation neutron analysis RNAA radiochemical separation neutron activation analysis also defined in list of acronyms. 

The detection limits of the old methods for the determination of arsenic (10) were too high to determine arsenic in uncontaminated biological samples. With the invention of instrumental techniques, such as flame atomic absorption (emission) spectrometry, graphite furnace atomic absorption spectrometry, neutron activation analysis, inductively coupled plasma atomic emission spectrometry, and inductively coupled plasma mass spectrometry, the ubiquity of arsenic in our environment was proven. The improvement of the analytical techniques has changed the reputation of arsenic from a poisonous substance to an essential trace element at least for warm-blooded animals (11). An arsenic requirement for humans cannot be deduced from these animal experiments. In recent literature, there are certainly more hints that arsenic might be an essential trace element for humans, but there is still a lot of future research work necessary to prove this. 

The achievable product activity depends on the photon energy and flux density of the activating source (Figure 1). Generally, the difference in detection limits among the elements is nowhere near as large as in neutron activation analysis. Typically, the detection limits, assuming purely instrumental analysis, lie between 0.001 and 1 pg, whereas in thermal... 

Neutron activation analysis (NAA) is one of the most important nuclear techniques for nanometallome quantification, as it can simultaneously measure more than 30 elements in a sample. The detection limits of NAA range from 10 to 10 gg In typically instrumental NAA, stable nuclides ( Z, the target nucleus) in the sample undergo neutron capture reactions in a flux of (incident) neutrons. The radioactive nuclides the compound nucleus)... 

The determination of Pb by reactor activation normally requires chemical separation of the 3.3 h pure emitter ° Pb. The use of the short-lived isomeric state 207mp j activated by the Pb(n,y) ° Pb and PbfnjnO Pb reactions is a useful instrumental alternative. The method has been investigated by Lukens using the triga reactor, and by Wiernik and AmieF and Henkelmann et Again the sensitivity of the method will depend upon the reactor neutron spectrum used. In the latter case, a reactor fast-neutron flux of 1.8 X10 cm s" allowed analysis with a limit of detection of 200 MS, somewhat poorer than the other methods. However, in such a flux spectrum the interference from other (n,y) activations will be considerably reduced. 

---