Anal. Chem. 1994,66, 229R-251R
Nuclear and Radiochemical Analysis William D. Ehmann,. J. David Robertson, and Steven W. Yates
Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055 Review Contents Books and Reviews Neutron Activation Methods Instrumental Thermal Neutron Activation Analysis Reactor Epithermal and Fast Neutron Activation Analysis Chemical and Radiochemical Neutron Activation Analysis Prompt y Neutron Activation Analysis, in Vivo Analysis, and Neutron Depth Profiling Neutron Activation Analysis with Accelerator-Generated Fast Neutrons Other Activation Methods Charged-Particle Activation Analysis (CPAA) Photon Activation Analysis (PAA) Ion Beam Analysis Particle-Induced y-Ray Emission (PIGE) Rutherford Backscattering Spectroscopy (RBS) Other Nuclear Reaction Analysis (NRA) Techniques Nuclear Microprobes Isotope Dilution Analysis (IDA) Direct Counting of Natural and Long-Lived Radionuc1ides Transmission, Absorption, and Scattering Methods Radioactive Tracers Isotopic Dating Methods Standards for Elemental Analysis Instrumentation Data Analysis and Computational Methods Conclusion
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In this review, our fifth under the current title and the final for our senior author before his retirement, we have restricted ourselves to topics dealing with the use of nuclear properties for chemical and elemental analysis. The material covered is similar to that of our previous efforts in this series, and once again, we have attempted to reduce the size of the review. Many applications have been relegated to tables, and we have become more critical in our evaluation of reported advancements. A description of the major developments in the diverse subfields included under this title is provided in the brief text associated with each section. As has become our practice, we have based this review primarily on a computerized search of Chemical Abstracts (November 1,1991 to November 1,1993) with “radiochemical analysis” as the primary search term. In addition, we have performed a number of more selective keyword searches using other databases, such as Current Contents, Medline, and Science Citation Index. It was again necessary to perform an independent search of INSPEC, which includes the Physics Abstracts database, in order to cover adequately the topic of ion beam analysis, since papers on these topics were not typically found under “radiochemical analysis”. In an attempt to maximize the utility of the extensive bibliography ac0003-2700/94/0366-0229814.0010 0 1994 American Chemical Society
companying this review, we have consciously limited consideration of publications ‘in languages less commonly used in major international scientific journals, unless the material is unique. Chemical Abstracts, Physics Abstracts, or Medline citations are appended to all non-English publications and less readily available reports. As usual, we hope our selections are representative of the field, but we make no claims as to completeness of coverage.
A. BOOKS AND REVIEWS As in our past reviews, we have segregated books and reviews from original research publications and presented a selected listing of these resources in tabular form (A1-A68). It should be noted that we have included only those reviews written in English in Table 1, but important reviews in other languages appear in many of the following sections. New books dealing with nuclear and radiochemical methods of analysis are rare. For this reason, we have attempted to emphasize them in Table 1 and briefly summarize the contents of three of these monographs. Fundamentals of Radiochemistry ( A I ) is designed to present an overview of the principles, objectives, and methods of radiochemistry and how they are applied to various fields of chemistry. Following a somewhat historical introduction, the essential features of radioactivity and nuclear chemistry are presented in a concise and insightful manner. Adloff and Guillaumont then lay the foundation (“bricks and tools” in their language) for subsequent discussions of chemical reactions, radiotracers, and various radiochemical methods. The final chapters deal with the chemical behavior of a few (IO0 g. The delayed neutron technique has recently been used to determine uranium and thorium in limestone (B28) and tin mining slags (B29). The reaction 54Fe(n,p)54Mnis often used for reactor fast neutron metrology. Bars and Seren (B30) have developed an INAA method for the determination of the isotopic abundance of 54Fein fast neutron dosimeter foils and reactor structural materials. The experimental isotopic abundance of 54Fein natural iron obtained by this technique was close to the recommended value. An innovative INAA method for the quantitation of asbestos in bulk samples has been reported by Parekh et al. (B31). The method uses concentrations of “signature” elements as indexes of the contents of the several components and is based on determining one marker element for each component and solving a set of linear equations. The components selectively determined included chrysotile, amosite, gypsum, and fiberglass. Contents of the asbestos components in prepared mixtures agreed well (f5 to 15% relative) with the formulated values. As noted previously, many publications now report the use of the ko-standardization method in the quantitation of INAA results. Several comprehensive reviews of the method and its modifications have been recently published (A20-A22). Problems associated with true-coincidence corrections, the detector efficiency factor, escape peaks, sum peaks, treatment of cross-section data, variations of the neutron flux in the irradiation container, and deviations of the epithermal neutron spectrum from the ideal 1/E shape have recently been addressed in the literature (B32-B37). Compilations of ko factors for short-lived nuclides have been published by Hien et al. (B38) and Roth et al. (B39). Obrusnik et al. (B40) reported that the ko-standardization method yielded results that compared favorably with the routinely used Zn INAA single comparator method and suggested that the ko method can be successfully used in routine INAA practice. Papers reporting applications of the ko method with an emphasis on accuracy and precision assessment include analyses of natural and synthetic quartz ( M I ) , geochemical reference standards (B42), and ceramic materials (B43). A computer program, ROMOS, designed to facilitate radionuclide identification and calculate concentrations by INAA using the ko232R
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standardization approach has been described by Moens and Roos ( B 4 4 ) . Important publications by Antonov (B45)and Heydorn (B46) have addressed, respectively, systems for optimization of INAA experimental parameters and the need for quality control in activation analysis. Optimization of counting conditions in y-ray spectrometry has been examined by Lindstrom (847). He finds that, in general, the ultimate sensitivity in quantitating a given INAA spectrum is most dependent on detector efficiency, rather than good resolution, low background, or other detector quality factors. With careful detector and shielding selection, cosmic-ray interactions are the only remaining significant source of environmental y-ray background. It is acknowledged that in actual practice the choice of detectors for counting may not be so simple, due to large summing corrections, unresolved multiplets, sample shape, and other factors unique to the real sample. Bode and Lindstrom (B48) have examined the performance of very large standard and well-type Ge detectors in INAA. Detector sensitivities are given and the large detectors are compared to a 17% relative efficiency Ge(Li) detector, based on factors of performance, economics, and complexity. De Bruin and Blaauw (849) and Blaauw et al. (B50) have also evaluated y-spectrometry procedures as sources of error in INAA. Papers describing specific INAA corrections include the 1 5 4 E ~ interference in the determination of zirconium (B51), fission product spectral interferences in analyses of several matrices (B52, B53), errors in analyses for thorium in fecal material due to the variable thorium content of quartz irradiation vials (B54),and resonance self-shielding corrections necessary in the analysis of gold ores (B55).An epithermal technique to resolve reaction interferences from phosphorus and silicon in the determination of aluminum has been reported by Morrison et al. (B56). The importance of line shift and peak broadening corrections in the evaluation of NAA spectra has been discussed by Beier and Mommsen (B57).Tian and co-workers (B58)have studied parametric normalization for Ge detector full-energy peak efficiencies at different counting geometries in NAA. Using their technique, comparative analyses of activated samples and standards with extremely different gross activities can be easily accomplished. Uranium fission coefficients in the INAA of geological samples have been reported Guodong (B59). The use of pattern recognition methods of chemometrics has been applied to INAA data obtained from analyses of ancient glasses (B60),and the same group in Korea used factor analysis to evaluate multivariate data obtained from NAAof ancient coins ( B d l ) . Itoh and co-workers (B62) have counted tritium from the 6Li(n,a)3H reaction with a scintillation counter to determine low levels of lithium in natural water samples. A clever technique to correct for liquid sample volume variations in INAA based on measurement of the 1294-keV y-ray photopeak of 41Ar produced from air trapped in the irradiation vial has been reported by Haverland (B63). The use of finepowdered Altos and Si02 with their original content of impurities (up to 40 elements) for INAA standards has been proposed by Nazarov et al. (B64). The commercial reagent oxides were found to be homogeneous (SD I2%) with respect to their original impuritycontents and when doped
with additional elements. Original impurity concentrations were often lower than in currently available standard reference materials. The use of information theory in the selection of reference standards for quality assessment in INAA has been explored by Obrusnik and Eckschlager (B65). Examples based on analyses of biological and environmental samples are also presented. New computer programs specifically designed for NAA have been published by Beeley et al. (B66) and Kennedy and St-Pierre (B67). Both are designed to be run on personal computers. Guinn and Gavrilas-Guinn (B68) have applied their INAA advance prediction computer program (APCP) to 10 biological, food, coal, and water reference materials. A proposed rule of thumb for INAA is to use an irradiation time, decay time, and counting time (if feasible) equal to approximately the half-life of the radionuclide determined. For the 280 radionuclide/material combinations traced, the rule predicted the best set of parameters for 67%, was off by one set for 31%, and failed by two sets for only 2%. Representative recent applications of INAA, with emphasis on those appearing in English and/or in widely available journals, are listed in Table 2. Reactor Epithermal and Fast Neutron Activation Analysis. As noted previously, few papers dealing with reactor epithermal neutron activation analysis were published in this review period. Landsberger and co-workers (B179, B180) have used a Compton suppression system to enhance the ENAA determination of cadmium in airborne particulates from tobacco smoke and some biological reference materials. Detection limits of 10-20 ng/g were reported using the 114Cd(n,y)11Td 'lSmIn 'lsSn reaction and decay sequence and counting the 336.3-keV IT y ray from IlSmIn. Shubina and Kolesov (B181)have carried out numerical modeling for y-ray spectra of radionuclides formed by reactor irradiation of samples in cadmium, boron, and both cadmium and boron filters. Optimum experimental parameters have been calculated for determination of trace elements in rocks by ENAA. A cadmium filter is used for optimum determination of Ag, Au, Ba, Br, Eu, Gd, Hf, Ir, Rb, Sn,Sr, Th, U, and Yb. A boron filter is applicable to the determination of Cs, Ga, Ni, Sm, Ta, and Tb. The cadmium-boron filter was selected for the determination of As, La, and W. Obrusnik and Bode (B182) used polyethylene sample capsules and short, 15-min, irradiations to analyze several standard reference materials. Epithermal flux gradients were determined by use of Au-Zr flux monitors. In one of the few examples published that couples postirradiation radiochemical separations with ENAA, Sims and Gladney (B183)employed alumina ion-exchange columns to separate and determine As, Mo, Sb, and W in silicate rock samples, following a I-h epithermal neutron irradiation. Malik and Parry (B184) reported that underestimations of gold contents in ores due to self-shielding in ENAA ranged from 1 1% for particles 1 5 3 pm in diameter to 33% for 150-250-pm particles. A reduction factor of 5% was reported for gold in Canadian reference ore MA- 1. Examples of the use of pulsed fast reactor neutrons at the IBR-2 reactor for NAA of environmental, geological, and food samples have been reviewed by Nazarov et al. (B185). Similarly, the analytical potential of the BOR 60 fast neutron
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Table 2. Selected Appllcatlom of Conventlonal Incrhumental Thermal Neutron Actlvatlon Analysls
archaeological samples ceramics, pottery, glasses coins metal artifacts mortars biological samples general aquatic and marine biota medicinal plants snake venom environmental samples general atmospheric samples, aerosols, dust, volcanic gases industrial raw materials, products, wastes waters foods, diets, tobacco products Australian composite diet Chinese cigarette coastal fish corn honey miscellaneous foods forensic samples bomb debris hair plant geological samples general cosmic spherules fossil fuels coal and coal ash crude oils kerogen ores, separated minerals asbestos borosilicates diamonds gold ores metallic minerals of Jamaica quartz uranium and thorium ores zirconium minerals rocks, rock systems Nigerian rocks Red Sea basalts West Bengal, India, rocks West Malaysian limestones sands, sediments, soils, soil gases human tissues body fluids bone brain breast tissue fecal ash hair kidney liver lung teeth materials, industrial products alloys, metals ceramics, refractory materials plastics quartz glass semiconductors, pure silicon, silicon processing superconductors ultrapure materials pharmaceutical science activable microspheres drugs and medicines sol particle immunoassay with colloidal gold
B6, B43, B57, B60, B69-B78 B17, B61 B79 B80 B20, B25 B81, B137 B18, B82-B83 B84 A32-A35, B12, B20, B25, B40, B68, B85, B86 A19, A23, B87-B99 B16, B19, B29, B99, BlOO B l l , B15, B62, B101-B103 B9, B104 B105 B106 B107 B108 B9, B25 B109 BllO Blll A10, A37, B6, B23, B42, B59 B4, B112 B26, B96, B113-B115 A44, B116, B117 A4 1 B3 1 B118 B119 A36, B55, B120 B121 B122 B53, B123 B51 B124-B126 B127 B128 B28 B 129-B137 B138-BI40 B141-B 143 B144-B148 B149 B54 B146, B150, B151 B146 B146, B152 B146 B153 B10, B13, B154-Bl58 B43, B159-B161 B 162-B 164 B54 A47, B6, B19, B41, B165-B172 B19, B173 A48 B174, B175 B18, B82, B83, B176, B177 B178
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Table 3. Selected Appllcatlons of EpHhermal and Reactor Fast Neutron Actlvallon Analysis
biological samples environmental samples general air particulates sewage tobacco smoke foods geological samples ores and rocks sapphires sediments and soils materials, industrial products a I u min a nuclear safeguard materials
B179, B182, B187 B185 A23 B187 B180 B185 B181, B183-B185, B187, B190 B188 B182, B187 B187 B189
reactor for determination of Ag, Au, Cd, Hg, and Pb by use of (n,n’) reactions has been discussed by Naumovet al. (B186). Additional selected applications of ENAA for this review period are listed in Table 3. Chemical and Radiochemical Neutron Activation Analysis. We have again combined single-element or group preirradiation concentration methods together under the classification of chemical neutron activation analysis (CNAA). Postirradiation single-element or group separations are categorized as radiochemical neutron activation analysis (RNAA) methods, although some authors use the acronym RNAA for both approaches. Current trends in RNAA and potential future applications are summarized in recent reviews by De Bruin (A18),Parry (A24),and De Goeij and Woittiez (A25). Parry (A24)concludes that the use of RNAA is unlikely to expand significantly in the future, but will continue in specialized areas (e.g., analyses of platinum group and rare earth group elements), RNAA is especially useful when concentrations are below the micrograms per gram level and alternate techniques suffer from losses or contamination during dissolution. Dybczynski (B191) has surveyed the role and uses of ion-exchange chromatography and extraction chromatography in NAA. Both CNAA and RNAA approaches are included and the importance of factors such as resin crosslinking and temperature is addressed. Perhaps the most novel approach in this area during the review period is that of Artem’ev (B192),who has developed pyrometallurgical methods for both CNAA and RNAA. ”Classical” fire assay methods have long been used for concentration of gold, silver, and other noble elements for conventional spectrometric analyses. In his approach, defined as “microrefining melting (MRM)”, dispersed elements in low concentration can be quantitatively extracted from liquid metal-molten salt systems into metal collectors such as bismulth, lead, tin, copper, or iron. The same type of system may also be used to concentrate trace elements into the molten ionic salt phase when high-purity metals are analyzed. The extraction percentages for 17 elements into molten lead, tin, and iron collectors are listed. Examples of the application of the technique in the analyses of copper ore reference materials, high-purity aluminum, and high-purity mercury are presented. Another interesting approach to RNAA uses substoichiometric extraction and milligram amounts of carrier to extract an element from solutions of both a biological sample and a microgram-level elemental standard irradiated simultaneously 234R
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(B193). In this study by Khan and Turel, mercury in biological samples was determined by substoichiometric extraction with ethyl thioacetoacetate into chloroform. Schelhorn et al. (B194)have demonstrated the advantages and disadvantages of using radiotracers incorporated in the carrier for chemical yield determinations in RNAA. Chemical speciation analyses via CNAA precipitation reactions for the selective determination of arsenate ion and for antimony(II1) and -(V) in natural waters have been reported by Van Elteren et al. (B195) and Sun et al. (B196),respectively. A two-step procedureinvolving precipitation and ion-exchange chromatography has been successfully used by Kueppers and Erdtmann (B197) to determine traces of phosphorus in gallium arsenide. The selectivity of the method is improved by use of Cerenkov counting of the high-energy 32P@ particles, a process that discriminates against detection of lower energy interference @ particles. Ion chromatography with continuous UV detection for online yield determination has been used by Woittiez et al. (B198) for chromium analyses in biological samples. Woittiez et al. (B199) have also used HPLC with on-line continuous UV detection for multielement RNAA separations with simultaneous yield determination for cobalt in biological samples. Finally, an interesting comparison of results from bone analyses by RNAA, GFAAS, Zeeman GFAASs, and ICP-AES has been published by Minoia et al. (B200). Selected representative examples of CNAA and RNAA applications for the current review period at listed in Table 4. Prompt y Neutron Activation Analysis, in Vivo Analysis, and Neutron Depth Profiling. As noted previously, prompt y neutron activation analysis is an area of significant growth and this trend is likely to continue with the establishment of several new “cold neutron” facilities. Recent general reviews of the field are listed in Table 1 (A26-,430). The facilities for PGNAA at the National Institute of Standards and Technology (NIST), Gaithersburg, MD, have been described by Lindstrom and co-workers (B254,8255). They note that PGNAA has its greatest applicability in the determination of non-metals such as H, C, N, Si, P, and S in geological and biological samples. Because of the lower neutron fluence rates in external reactor neutron beams, PGNAA has typically 2-3 orders of magnitude less sensitivity than INAA for many other elements, although trace element sensitivity is still adequate todetermine elements with high thermal capture cross sections such as B, Cd, and Gd. The cold neutron facility at NIST provides PGNAA sensitivities that are typically 4-6 times better than the older thermal neutron PGNAA facility at NIST. The cold neutron facility at NIST has been initially used for hydrogen determinations in materials such as fullerenes and superconductors, where the PGNAA cold neutron sensitivity improvement is 7-fold and the hydrogen background in the system is 30-fold lower than for previously used thermal neutron PGNAA at the facility. Descriptions of PGNAA facilities at JRR-3M in Japan (B256),the Budapest Research Reactor in Hungary (B257), and the external neutron guide laboratory (ELLA) at Julich, Germany (B258, B259) have also recently been published. All incorporate cold neutron guide facilities. In spite of the interest in constructing cold neutron PGNAA facilities,
Table 4. Selected Applkatlonr of Chemlcal and Radlochemkal Neutron Actlvatlon Anaiydr
Preirradiation Separation of Matrix or Preconcentration (CNAA) absorption on charcoal or carbon filters Se in organic samples, fodder, and reference standards I-, IO3- and total inorganic I in seawater trace elements in volcanic gases coprecipitation and related methods As(V) in water samples Sb(II1) and Sb(V) in water samples Hg in waters and foods by copptn of Hg on CuS followed by RNAA ion exchange trace elements in waters and biological materials by organic reagent pptn Cd in seawater by copptn of Cd dibenzyldithiocarbamate with phenolphthalein use of enriched 116Cd and 156Dy as activable tracers for yield determination in a preconcn iron hydroxide copptn step prior to NAA of coal fly ash, rocks, and soils pptn to preconcentrate arsenate ion and Sb(II1) and Sb(V) distillation/ high-temperature processes separation of I from soils by heating and collection on charcoal pyrometallurgical methods for preconcentration ion exchange, adsorption trace elements in Ga AI in biological samples Cr in urine and serum Ga in biological and environmental samples rare earths in high-purity La203 trace elements in acid rain size discrimination ultrafiltration of erythrocytes filtration and ultrafiltration of species in urban streams solvent extraction trace elements in Ga rare earths in high-purity scandia organobromine and organochlorine in waters, sediments, and biological samples Re in rocks miscellaneous noble metals by fire assay 1291 in large soil samples Postirradiation Separation (RNAA) general surveys coprecipitation and related (often combined with other methods) As, Mo, Sb, and Se in water, loess, and volcanic glasses by Biz& copptn Se in diet samples employing both volatilization and pptn Th and U in high-purity Si and AI by anion exchange and LaF3 copptn Pd, Ir, and Pt sepd by solvent extraction, Cs by pptn and the rare earth elements by cation exchange in mantle-derived magmatites multielements in human brain tissue by solvent extraction and pptn separations Se by pptn of Se metal, As, Cu, and Hg by sulfide pptn in fish noble metals and allied trace metals in rocks by Te copptn trace elements in lithium niobate separation by pptn of the hydrous oxide of Nb and subsequent ion exchange pptn and ion exchange of Nb and subsequent ion exchange pptn and ion exchange for P in gallium arsenide distillation/ high-temperature processes Se in diet samples employing both volatilization and pptn Cr in fish by distillation of Cr02C12 high-temperature extraction of Ir and Hg from rocks in a NiS melt and distillation of Hg ion exchange, adsorption I in urine using an iodinated ion exchange resin Cs and Rb in geological samples using a zeolite column U and Th in microelectronic materials by anion exchange multielements in silicon nitride by cation and anion exchange followed by solvent extraction for Cu; results are compared to ICP-AES and ICP-MS multielements in waste landfill leachate by GFAAS and RNAA employing inorganic ion exchangers HAP, HMD, and CNAA with ion-exchange resin Chelex-100 for preirr separation of V and Mn Ir in Precambrian-Cambrian boundary rocks by use of a thiourea chelate resin U, Th, and other elements in high-purity W by anion exchange U and Th in high-purity AI by ion exchange multielements in high-purity Ta by anion exchange removal of HNa and related absor tion properties of a composite hydrated antimony pentaoxide (HAP)-divinylbenzene ion excianger applied to the RNAA of biological samples multielements in blood serum by ion exchange multielements in geological and biological samples by resin and inorganic ion exchange and solvent extraction Pt in environmental and geological samples by polyurethane foam separation of the lWAudaughter of IWPt Cd, Co, Cr, and Mo in biological samples by ion exchange with both Chelex-100 and BioRad AB2X8 ion chromatography with UV detection for Cr in biological samples solvent extraction Cd, Hg, and Sb in biological samples by extraction into 4-(5-nonyl)pyridine-benzene from 2.0 M HC1 U in blood, urine, and hair by extraction of U with 50% tri-n-butyl phosphate (TBP) in toluene multielements in high-purity In using the TBP-HBr extraction system P in high-purity Ge using extraction chromatography with dioctyltin diacetate rare earth elements in raw materials and products of the rare earth industry by extraction chromatography several stage solvent extraction procedure to determine Sr in blood serum and blood cells with a final extraction of Sr into 1 M oxime in chloroform from a NaOH solution I in drinking water by extraction at pH
