Radioanalytical chemistry

INAA was recently reviewed [452,453]. Various books deal with radioanalytical chemistry and nuclear methods of analysis [435,454-458]. A nuclear spectrometry handbook is available [459]. 

J. Tolgyessy and M. Kyrs, Radioanalytical Chemistry, EUis Horwood, Chichester (1989). 

Although many other types of nuclear reaction are possible as a result of high neutron fluxes, these two are the ones of prime importance in radioanalytical chemistry. The two principal requirements for a reaction to be useful analytically are that the element of interest must be capable of undergoing a nuclear reaction of some sort, and the product of that reaction (the daughter) must itself be radioactively unstable. Ideally, the daughter nucleus should have a half life which is in the range of a few days to a few months, and should emit a particle which has a characteristic energy, and is free from interference from other particles which may be produced by other elements within the sample. 

Ishii, D., Hirose, A., and Horiuchi, I., Studies on micro-high-performance liquid-chromatography. 6.Application of microscale liquid-chromatographic technique to anion-exchange separation of halide ions. Journal of Radioanalytical Chemistry A5( ), 7-14, 1978. 

Advanced Radioanalytical Chemistry Group, Physical and Chemical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA Jose A.P. Piedade... 

The most important solid-phase separation materials for column-based separations in modern radioanalytical chemistry are extraction chromatographic materials, and these have been particularly important in automated radioanalytical chemistry. Solid-phase extraction materials based on the covalent attachment of ligands to solid supports also exist, and they have found application in large-scale separation processes for waste or effluent treatment.22 25 They have been commercialized as Analig or SuperLig materials by IBC Advanced Technologies (American Fork, UT). However, they are less well characterized or used for small-column analytical separations. 

The authors thank their associates in the Environmental Radiation Center, EOSL, GTRI, especially Robert Rosson and Liz Thompson for their extensive and valuable editorial support and Jeff Lahr, Ramon Garcia, and David Crowe for assistance in the laboratory. Our sympathy goes to the family of Ramon Garcia, who died while work on the Radioanalytical Chemistry text and experiments was in progress. 

The Editorial Advisory Board members who worked on the Radioanalytical Chemistry Text also reviewed this manual and advised the authors. We thank ... 

The experiments in this manual were selected to accompany the textbookRadio-analytical Chemistry. The manual is intended to acquaint the senior or graduate student with the practices of radioanalytical chemistry and develop some familiarity with the various techniques and methods commonly used in the radioanalytical laboratory and the counting room. The authors believe that only hands-on experience can translate the guidance provided by a textbook to an understanding of the applications that form the basis of this aspect of radiochemistry. 

The focus of the experiments is on the work in the radioanalytical chemistry laboratory - initial sample processing, radioanalyte purification, and preparation of the sample for counting. Certain aspects of radiation detection, such as counting efficiency and self-absorption for the various radiations, are addressed in these experiments. We expect that the student learns about the principles and applications of radiation detection instruments in a separate radiation detection course, which can be presented before, after, or in parallel with this course. 

The specific practices and laboratory skills associated with individual experiments are briefly identified below to provide the instructor with an overview and assist in selecting experiments. A discussion of the principles to be presented and emphasized is discussed in the following section of this Introduction. The subsequent section emphasizes the safety precautions to be maintained in the radioanalytical chemistry laboratory. 

Knowledge of pertinent radioanalytical chemistry principles, including the appropriate vocabulary. 

The primary function of the radioanalytical chemistry laboratory is to prepare samples for radioactivity measurement. The radioactive species are identified by detecting the radiation that they emit. The goal of the analysis is to produce a sample for counting that has no interference from other radioactive species and to quantify the recovery of the radioactive species in the analysis. 

The more the analyst knows concerning the numerous nuclear and radiochemical properties and characteristics of the analyzed radionuclide, the easier it is to select the most appropriate analysis and to resolve problems in ascertaining the quality and validity of the results. Especially for non-routine sample analysis, the nuclear properties of the radionuclide of interest must guide selection of the method of analysis and detection. The appropriate passages of the accompanying text Radioanalytical Chemistry are referenced when more detailed discussions are needed. 

The execution of each step requires a range of activities, each of which are covered thoroughly in the appropriate chapters of the Radioanalytical Chemistry textbook. Sample separation and purification are of particular concern, in the sense that no reasonable counting data can be obtained and... 

Initial Sample Preparation. When received, the sample must be handled according to the proper protocol to maintain its chemical and legal integrity. Some pretreatment to preserve the sample usually is performed at collection time and should be properly described in chain of custody documentation that accompanies the sample, as described in the Radioanalytical Chemistry text. 

Analyte half-lives need to be considered to arrange for rapid collection, transfer to the laboratory, and radioanalytical chemistry processing before they decay to poorly-detectable low amounts. Types of emitted radiation control the detector that must be purchased, calibrated, and operated. Radiochemists and radiation-detector operators who commonly handle a specific category of radionuclides become skilled in purifying and counting these radionuclides. 

Among common radionuclide sources are the natural environment, fallout from nuclear weapon tests, effluents from nuclear research laboratories, the nuclear power fuel cycle, radiopharmaceutical development, manufacturing, and various application, teaching and research uses. Decontamination and decommissioning activities at former nuclear facilities and the potential of terrorist radionuclide uses are current topics of interest for radioanalytical chemistry laboratories. Simplified information on the numerous radionuclides is conveniently found in Charts of the Nuclides such as Nuclides and Isotopes (revised by J. R. Parrington, H. D. Knox, S. L. Breneman, E. M. Baum, and F. Feiner, 15th Edition, 1996, distributed by GE Nuclear Energy). 

Laboratories specialize in analyzing radionuclides at either high or low levels. Personnel-protection installations and practices are required for high levels of radiation from high levels of radionuclides. Low-level radioanalytical chemistry requires separation from high levels because results are easily undermined by contamination. 

For the purposes of these experiments, the following practices are strongly encouraged. The instructor may insist on additional practices and recommend reading a designated safety manual. In addition, Chapter 14 of the textbook Radioanalytical Chemistry covers the topic of laboratory safety. The student s responsibility is to follow all rules presented here, by the instructor, and in the safety manual. 

Always treat laboratory equipment in a radioanalytical chemistry laboratory as if it contained or had contained radioactive material. Glassware that has been used with radioactive material should be segregated and properly labeled. 

To practice pipetting small volumes and weighing small quantities that are encountered in a radioanalytical chemistry laboratory. 

Prepare Data Table 1.3. Calculate the percent deviation (+/-) of the experimental volume recorded from the volume value marked on the pipette. See the Radioanalytical Chemistry textbook, Section 10.3 Measurement Uncertainty, for guidance on calculating standard deviation. 

With minor exceptions, the samples handled in a radiochemical laboratory are eventually measured with radiation detection instruments. The types of counting equipment in the counting room depend primarily on the scope and purpose of the radioanalytical chemistry laboratory mission. Common detectors of this type are listed in Table 2.1. 

See Appendix 6 and the Radioanalytical Chemistry textbook for definitions and formulae for calculating count rate and standard deviation (a) with error propagation. 

Try to explain the shape of the counting efficiency vs. energy curve for the germanium detector. Refer to your Radioanalytical Chemistry textbook, Chapters 2 and 8. 

The formula for the self-absorption factor is exact for gamma rays (see Experiment 3) but approximate for beta particles. That it is applicable at all is due to the near-linear decrease of the logarithm of the count rate with absorber thickness of a beta-particle group (see Figure 2.6 in the Radioanalytical Chemistry textbook). The obvious deviation is that this relation ends at the range of the maximum-energy beta particle, whereas it continues indefinitely for gamma rays. 

To prepare and standardize carriers for radioanalytical chemistry procedures. 

Direct Dilution of a Certified Solution. When standard tracer solutions are purchased from commercial sources, detailed certificates must accompany them (see Section 11.2.6 in Radioanalytical Chemistry). Because the activity of the certified tracer solution usually is greater than needed for tracing individual samples, one or several sequential dilutions must be performed meticulously to produce the solution from which an aliquot will be pipetted into the samples. Dilutions should be prepared in a chemical form identical to the original solution with regard to type and concentration of acids and reagents to assure tracer solubility and stability. The analyst should perform dilutions by weight rather than by volume for precise work. The final dilution is usually planned to obtain a solution from which about 0.05 Bq is pipetted into a sample that contains that amount or less of plutonium analyte. 

Calculate the minimum detection limit of tritium for the counting system in this experiment. (See Section 10.4.2 of your Radioanalytical Chemistry textbook for guidance on calculating the MDA). 

Step 3. Read about the radiochemistry of iodine to improve your understanding of the radioanalytical chemistry of iodine. An old but helpful monograph is Radio chemistry of Iodine, NAS-NS-3062, by Milton Kahn and Jacob Kleinberg, Office of Scientific and Technical Information, US DOE, 103 pp (1977). A copy may be obtained from the instructor, the library, or internet search. Also read about ion-exchange theory and practice, and in particular, the relative affinity of anions for strong-base ion-exchange material. 

Proper preparation of biological solids for radiochemical analysis is essential for obtaining valid radioanalytical chemistry results. The samples often must be large because the radioactivity levels are low. Gamma-ray spectral analysis is the preferred method of radiation measurement because it requires little preparation. If gamma-ray spectral analysis of the untreated sample is not feasible because few or no gamma rays are emitted, the sample must be dissolved. Dissolution is almost always required for alpha- and beta-particle analysis. The first step usually reduces the mass of the solid sample and prepares it for dissolution. 

The process for converting the vegetation sample to a soluble form is selected for convenience, familiarity, safety, and optimal removal of interfering substances. A problem in dissolving salts of heavier Group IIA elements with mineral acids is that they may be insoluble sulfates. The most common method for bringing insoluble sulfates into solution is to subject the sample to hydroxide-carbonate fusion (fusion is discussed in Section 4.6.2 of your Radioanalytical Chemistry text). The fusion is performed in a metal crucible that is relatively insoluble under the fusion conditions. The temperature must be sufficiently high to melt the sulfates and convert them into carbonates. The carbonates are then dissolved to prepare the sample for analysis. 

Step 4a. For microwave-assisted, digestion, follow the procedure developed for the microwave system in the laboratory. Note that total dissolution of the solid is required for radioanalytical chemistry, whereas partial dissolution is acceptable for other analytical processes if the method has been tested for fractional recovery. Several references are given below that may be helpful in developing or using this method. 

To review the literature for a radioanalytical chemistry method to purify plutonium from other radionuclides, notably actinides, and from interfering stable substances in an environmental sample and to compare the method selected by the student with the methods in Experiments 15 and 16. 

Uranium in nature may be measured either radiometrically or chemically because the main isotope - 238U - has a very long half life (i.e., relatively few of its radioactive atoms decay in a year). Its isotopes in water and urine samples usually are at low concentrations, for which popular analytical methods are (1) radiochemical purification plus alpha-particle spectral analysis, (2) neutron activation analysis, (3) fluorimetry, and (4) mass spectrometry. The radiochemical analysis method is similar in principle to that of the measurement of plutonium isotopes in water samples (Experiments 15 and 16). Mass spectrometric measurement involves ionization of the individual atoms of the uranium analyte, separation of the ions by isotopic mass, and measurement of the number of separated isotopic ions (see Chapter 17 of Radioanalytical Chemistry text). 

When counting data with their associated uncertainty values are added, subtracted, multiplied, or divided with other counting data, or constants, the propagation of the error may be estimated in the final answer. Since both numbers will have associated uncertainties, it is necessary to use the correct relationships to establish the final error. The final error from that manipulation (when two data with their errors are used) will always have a final error larger than either of the errors of the two initial data. For more detailed treatment of counting errors, see Radioanalytical Chemistry, Chapter 10. 

G. R. Gilmore, G. W. A. Newton, Radioanalytical Chemistry, in Radiochemistry, Vol. 2, Specialist Periodical Reports, The Chemical Society, London, 1975. 

Toelgyessy, J.. Kyrs, M., 1989. Radioanalytical Chemistry. Ellis Horwood, Chichester, p. 345. 

Radioanalytical chemistry is devoted to analyzing samples for their radionuclide content. For this purpose, the strategies of identifying and purifying the radioelements of interest by chemical methods, and of identifying and measuring the disintegration rate ( activity ) of radionuclides by nuclear methods, are combined. Radioanalytical chemistry can be considered to be a specialty in the subdiscipline of nuclear and radiochemistry. 

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