Neutron activation analysis with radiochemical

Trace Elements in Coal by Neutron Activation Analysis with Radiochemical Separations... 

Procedures for the determination of 11 elements in coal—Sb, As, Br, Cd, Cs, Ga, Hg, Rb, Se, U, and Zn—by neutron activation analysis with radiochemical separation are summarized. Separation techniques include direct combustion, distillation, precipitation, ion exchange, and solvent extraction. The evaluation of the radiochemical neutron activation analysis for the determination of mercury in coal used by the Bureau of Mines in its mercury round-robin program is discussed. Neutron activation analysis has played an important role in recent programs to evaluate and test analysis methods and to develop standards for trace elements in coal carried out by the National Bureau of Standards and the Environmental Protection Agency. 

As mentioned before, two interlaboratory studies were organised prior to certification, involving ca. 15 laboratories using techniques such as cold vapour atomic absorption spectrometry, direct current plasma atomic emission spectrometry (DCP-AES), differential pulse anodic stripping voltammetry (DPASV), microwave plasma atomic emission spectrometry (MIP-AES), electrothermal atomic absorption spectrometry (ETAAS) and neutron activation analysis with radiochemical separation (RNAA). 

RNAA Neutron activation analysis with radiochemical separation... 

Nuclear Methods - Neutron Activation Analysis with Radiochemical Separation (RNAA)... 

Some relevant terms for activation analysis are activation analysis, neutron activation analysis (NAA), instrumental neutron activation analysis (INAA), neutron activation analysis with radiochemical separation (RNAA), photon activation, neutron capture prompt gamma activation analysis (PGAA), charged particle activation, autoradiography, liquid scintillation counting, nuclear microprobe analysis, radiocarbon (and other element) dating, radioimmunoassay, nuclear track technique, other nuclear and radiochemical methods. Briefly, the salient features of some of the more popular techniques are as follows ... 

Gallium may be estimated in low-temperature coal ash by neutron activation analysis, with radiochemical separation. Amounts in the range 1—10 p.p.m. were determined. 

Dyhczynski, R.S. 50 years of adventures with neutron activation analysis with the special emphasis on radiochemical separations. J. Radioanal. Nucl. Chem. 303, 1067-1090 (2015). doi 10.1007/sl0967-014-3822-6... 

Byrne, A.R. and Benedik, L. (1991). Uranium content of blood, urine and hair of exposed and non-exposed persons determined by radiochemical neutron activation analysis, with emphasis on quality control, ScL Total Environ. 107, 143-157. 

The apphed pretreatment techniques were digestion with a combination of acids in the pressurized or atmospheric mode, programmed dry ashing, microwave digestion and irradiation with thermal neutrons. The analytical methods of final determination, at least four different for each element, covered all modern plasma techniques, various AAS modes, voltammetry, instrumental and radiochemical neutron activation analysis and isotope dilution MS. Each participating laboratory was requested to make a minimum of five independent rephcate determinations of each element on at least two different bottles on different days. Moreover, a series of different steps was undertaken in order to ensure that no substantial systematic errors were left undetected. 

Byrne AR, and Kucera J (1991) Radiochemical neutron activation analysis of traces of vanadium in biological samples A comparison of prior dry ashing with post-irradiation wet ashing. Fresenius f Anal Chem 340 48-52. 

During the late 1960s and early 1970s, neutron activation analysis provided a new way to measure bulk chemical composition. Neutron activation analysis utilizes (n,y) reactions to identify elements. A sample is placed in a nuclear reactor where thermal neutrons are captured by atoms in the sample and become radioactive. When they decay, the radioactive isotopes emit characteristic y-rays that are measured to determine abundances. Approximately 35 elements are routinely measured by neutron activation analysis. A number of others produce radioactive isotopes that emit y-rays, but their half-lives are too short to be useful. Unfortunately, silicon is one of these elements. Other elements do not produce y-ray-emitting isotopes when irradiated with neutrons. There are two methods of using neutron activation to determine bulk compositions, instrumental neutron activation analysis (INAA) and radiochemical neutron activation analysis (RNAA). 

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. 

Of the five stable Isotopes of zinc, only three ( Zn, Zn, and Zn) can be measured with (delayed gamma) Neutron Activation Analysis and hlgh-resolutlon gamma spectrometry. The required methodology for the measurement of Zn is the most stringent of the three isotopes and the necessary Radiochemical Neutron Activation Analysis has been developed and described in detail elsewhere (.8), The salient features of neutron activation of these three Isotopes are tabulated in Table li and from these, two points emerge First, with the availahility of thermal neutron... 

Rietz, B., Krarup-Hansen, A., Rprth, M. Determination of platinum by radiochemical neutron activation analysis in neural tissues from rats, monkeys and patients treated with cisplatin. Anal. Chim. Acta 426, 119-126 (2001)... 

A large number chondrites have been analyzed with instrumental and radiochemical neutron activation analysis using —250-350 mg samples of chondrites (Kallemeyn and Wasson, 1981 Wasson and Kallemeyn, 1988 Kallemeyn et al, 1991, 1994, 1996). Samples of this size can also be analyzed for many elements with comparable accuracy using X-ray fluorescence analysis (Wolf and Palme, 2001). Mean compositions of chon-drite groups are given by Lodders and Fegley (1998). 

The availability of high flux thermal neutron irradiation facilities and high resolution intrinsic Ge and lithium drifted germanium (Ge(Li)) or silicon (Si(Li)) detectors has made neutron activation a very attractive tool for determining trace elemental composition of petroleum and petroleum products. This analytical technique is generally referred to as instrumental neutron activation analysis (INAA) to distinguish it from neutron activation followed by radiochemical separations. INAA can be used as a multi-elemental method with high sensitivity for many trace elements (Table 3.IV), and it has been applied to various petroleum materials in recent years (45-55). In some instances as many as 30 trace elements have been identified and measured in crude oils by this technique (56, 57). 

Earlier methods used to determine mercury in biological tissue and fluids were mainly colorimetric, using dithizone as the com-plexing agent. However, during the past two to three decades, AAS methods - predominantly the cold vapor principle with atomic absorption or atomic fluorescence detection - have become widely used due to their simplicity, sensitivity, and relatively low price. Neutron activation analysis (NAA), either in the instrumental or radiochemical mode, is still frequently used where nuclear reactors are available. Inductively coupled plasma mass spectrometry (ICP-MS) has become a valuable tool in mercury speciation. Gas and liquid chromatography, coupled with various detectors have also gained much importance for separa-tion/detection of mercury compounds (Table 17.1). 

NAA, XRF, and isotope dilution analysis, by listing the parameters analytes determinable, concentration ranges, selectivity, analysis time and cost. Vandecasteele (1991) presents a review of recent developments and trends in instrumental and radiochemical neutron activation analysis as well as charged particle activation analysis and performance comparison with ICP-MS. 

The fundamental principle behind analysis by activation analysis is activation or excitation of an atomic nucleus by exposure to radiation such as neutrons, protons or high-energy photons with subsequent measurement of emitted sub-atomic particles or radiation. The most common aspect of the technique involves activation with neutrons in a nuclear reactor and measurement of delayed emitted gamma rays, denoted neutron activation analysis, either instrumental neutron activation analysis (INAA) or neutron activation followed by radiochemical separation (RNAA) in which the element of interest is chemically separated from the matrix after irradiation to provide for better, unimpeded counting. 

WoiTTiEZ JRW, Lagerwaard A, VoLKERS KJ and Tangonan MDC (1993) Radiochemical neutron activation analysis of chromium in hiolo cal materials using ion chromatography with on-line yield determination. J Radioanal Nucl Chem 169 229— 237. 

It is generally agreed that neutron activation analysis has shown great sensitivity for many elements. Absolute sensitivities of detection depend on the atomic weight of the element, the fractional abundance of the target nuclide, and its cross section for thermal neutrons (which are fixed values) as well as on the available neutron flux, the irradiation time, the decay period, and the counting efficiency of the detector (which are variable parameters). The formulae described under Fundamentals (vide supra) will make it clear that, unless conditions are exactly specified, published values cannot easily be compared especially as the definitions for sensitivity chosen by the investigators may be different. Experimental sensitivities may be idealized because of matrix problems, difficulties in radiochemical separations, and other analytical problems associated with the analysis of complex, real samples. 

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