Nuclear and radiochemical analysis - ACS Publications - American

Anal. Chem. 1986, 58,49 R-65 R 1. (6K) Reardon, P. A.; O’Brlen, G. E.; Sturrock, P. E. Anal. Chim. Acta 1084, 162, 175-87. (7K) Ridgway, T. H.; Mark, H. B., Jr. “Computerization in Electroanalytical Chemistry”; in White, R. E., Bockris, J. O’M., Conway, 8. E., Yeager, E., Eds. ”Comprehensive Treatise of Electrochemistry”; Plenum Press: New York, 1984; Vol. 8, Chapter 2. (8K) Yarnitsky, C. N. Anal. Chem. 1985, 57, 2011-15.

(2K) Brown, P. B.; Franz, G. N.; Moraff, H. “Electronics for the Modern Scientist”; Elsevier Biomedical Press: Amsterdam, 1982. Reviewed by Reeves, R. J. Electroanal. Chem. 1984, 161, 213-4. (3K) Cunningham, L.; Frelser, H. Larrgmuir 1085, 1, 537-41. (4K) Hara, M. Talanta 1985, 32, 41-3. (5K) McKubre. M. C. H.; Macdonald, D. D. “Instrumentation”; in White, R. E., Bockris, J. O’M., Conway, B. E., Yeager, E., Eds. “Comprehensive Treatise of Electrochemistry”; Plenum Press: New York, 1984; Vol. 8, Chapter

Nuclear and Radiochemical Analysis William D. Ehmann* and Steven W. Yates Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055

ative abstract in Chemical Abstracts (CA) can be cited. Laboratory or government reports and conference proceedings that may be difficult to obtain have generally been omitted. CA citations are appended to references where the language is other than English or where the publication is in a less accessible journal or report.

With this review, a change in authorship, title, and scope from a previous series of reviews in Analytical Chemistry under the title of “Nucleonics” is initiated. We feel the new title reflects an emphasis appropriate to this journal and the interests of many of its readers. In general, we have chosen to exclude articles in the areas of health physics, nuclear spectroscopy (unless directly related to analytical utility), nuclear engineering, fusion, radioactive waste disposal, fallout, and nuclear and particle physics. In contrast, topics clearly representing the use of nuclear properties for analysis are highlighted. Tor>icssuch as Darticle-induced X-ray emission (PIXE), plasma desorption mass spectrometry, radioimmunoassay, Mossbauer spectroscopy, and common radiotracer applications are now covered in reviews under other titles in this or other readily available journals. These latter research areas, although well populated by scientists trained in the fields of nuclear and radiochemistry, are treated briefly here. We cannot resist the temptation to comment on some topics not usually found in other reviews, but of general interest to nuclear and radiochemists. Included are topics such as neutrino research, discoveries of new elements, the search for decay of the proton, and new decay processes, even though they do not fit comfortably under the new title for this series. Along with many readers of the previous “Nucleonics” review series, we wish to express our gratitude to William Lyon and Harley Ross for their efforts to keep us up with the expanding literature of nuclear and radiochemical analysis. We hope that current readers will find this review useful and that not too many of your favorite topics will have been excluded. This review is based largely on a computerized keyword search of Chemical Abstracts for the period from mid-1983 to mid-November 1985. Approximately 50% of the nearly 2000 abstracts considered were found by searching with the keyphrase “radiochemical analysis”. Nuclear analytical chemistry is now clearly a mature field; breakthroughs in methodology are now rare, but innovative applications of nuclear techniques continue to increase. Some of the most interesting developments in the last few years have been the use of activatable (The term “activatable” is more commonly used in the radiochemical literature and will be used in the remainder of this review.) elemental or enriched isotope tracers in environmental studies, preirradiation derivatization or chemical separations to permit enhanced sensitivity or speciation, nuclear microprobe techniques, unique applications of prompt y neutron activation analysis, and accelerator-based dating methods that replace low activity counting methods. A complete review of applications is not possible within the editorial guidelines; however, we have chosen to include a few representative applications in each of a wide variety of scientific fields, and the reader should refer to our tabulation of more specialized reviews for sources of additional citations. Publications in less common languages are included in this review only where the material covered is not represented in a more widely used langu e. Publications in major scientific languages other than Enzish are included when an inform0003-2700/86/0358-49R$Og.50/ 0

A. BOOKS AND REVIEWS We have chosen to separate comprehensive books and other review papera from original research contributions. Table I contains a tabulation of selected reviews and books that may be of interest to many of our readers. The list is not exhaustive, but should provide starting points for further literature searches on specific topics. The appearance of a new book in the fields of nuclear and radioanalytical chemistry is a rarity. In the current review period three new books that should have broad appeal to researchers in nuclear and radioanalytical chemistry have been published. The first, entitled “Nuclear Analytical Chemistry” by Brune, Forkman, and Perrson (AI), provides an introduction to nuclear structure, decay processes, nuclear reactions, sources of particles and radiations interactions of radiation with matter, radiation detectors, nuclear electronics, and spectral analysis. In addition, approximately 200 of the 557 pages are devoted to the methodology of activation analysis and a review of its applications. Particle-induced X-ray emission (PIXE) and scattering techniques are only briefly mentioned. Unfortunately, very few of the references cited bear publication dates in the 1980s. This volume would serve well as a textbook for a course in radioanalytical chemistry at the college senior/first-year graduate student level or as an introduction to activation analysis for individuals trained in other disciplines. The second book is entitled “Neutron Activation Analysis for Clinical Trace Element Research, Vol. I and 11”by Heydorn (A2). In contrast to the previously mentioned book, this monograph is directed to a more advanced audience. The author is quite successful in bridging the gap between clinical and analytical scientists. This two-volume set contains many useful data tabulations and references. The third book entitled “Studies in Environmental Science, Vol. 22, Environmental Radioanalysis” by Das et al. (A3) provides a good introduction to activation analysis and PIXE as applied in the environmental field.

B. ACTIVATION ANALYSIS 1. Instrumental Thermal Neutron Activation Analysis

(INAA). In this section we cover the new developments in the methodology of INAA using reactor or isotopic neutron sources and selected applications. Publications combining neutron activation with postirradiation radiochemical separations of an element or group of elements (RNAA) are reviewed in Section B.7. One of the more interesting recent developments has been the use of elemental or enriched isotopic tracers along with INAA. Tsukada et al. ( B I ) have used enriched stable l16Cd @

1986 American Chemical Society

49 R

NUCLEAR AND RADIOCHEMICAL ANALYSIS

Table I. Selected Books and Reviews in Nuclear and Radioanalytical Chemistry Activation Analysis general errors hot atom and radiation effects molecular activation analysis photon activation, electron accelerators prompt y neutron activation in vivo lab, field, on-stream radiochemical separations general ion exchange preconcentration applications archaeology environmental studies general air particulates

AI-7, A69 A8 A9, AI0 A9 AI1 A12, A33 A13, A27 A14, A71 A15, A16 A17 A18 A3, A19, A20 A21

geology

general coal, shale, tar sand, petroleum exploration, mining and on-line processing industry general corrosion, wear semiconductors medicine in vivo

tissues, organs, and body fluids Isotope Dilution Analysis drugs 15N isotope dilution method, nitrogen fixation radioreceptor assay, radioimmunoassay rocks

substoichiometry Radiorelease Methods, Autoradiography Charged-Particle Reaction Analysis general proton-induced X-ray emission Rutherford backscattering surface analysis thin-film analysis nuclear microurobes

A22-24 A25 A26, A27 A28, A29 A30, A31 A32 AI2, A33, A34 A35 A36 A37 A38-40 A23 A41, A71 A42, A43 A44-47 A48, A49 A50-52 A44, A52 A53-58

as an activable tracer to monitor the preconcentration of Cd for its determination in biological samples. The element Sm has been used as a activable tracer in the study of insect predator/parasite-prey interactions (B2).Dysprosium has been similarly used to measure spray drift in the irrigation of winter wheat (B3).There would appear to be many potential applications for the use of activable stable isotope tracers in environmental research and pharmaceutical studies. Rahn and Lowenthal (B4)have used INAA and combinations of naturally occurring elemental activable tracers to study movements of regional pollution aerosols. The addition of activable elemental or enriched isotopic tracers at the site of origin of the pollution would appear to be a natural extension of these studies. The use of enriched isotope activable tracers in pharmaceutical doses would avoid the need to expose subjects to radiation from radioactive tracers in bioavailability studies. Other areas with good potential for future development include the use of preirradiation chemistry to mate an activable tracer to a second element of interest, which has less desirable nuclear properties, or to isolate a particular chemical species. Examples of these approaches include derivative activation analysis with an isotopic neutron source for the determination of P in commercial produds (B5)and molecular activation analysis based on the use of preirradiation separations to speciate selenium compounds in urine (B6). Additional developments in methodology include the use of intense pulsed neutron sources for compositional analysis (B7) or for monitoring mass flow rates in fluids (B8). Niese (B9)has pointed out the advantages of multisample P-7 coincidence spectrometry in reducing background in high sensitivity NAA, and Potts et d. (B10)claim improved sensitivity for INAA of rocks by simultaneously counting samples with both planar and coaxial Ge detectors. Arikan and Demirel (Ell)have demonstrated the accuracy of using characteristic 50R

ANALYTICAL CHEMISTRY, VOL. 58, NO. 5, APRIL 1986

Transmission, Attenuation, and Scattering Methods y-ray scattering neutron gages soil water management Standards for Elemental Analysis Well Logging oil and gas wells with a high-purity Ge detector Data Analysis and Computational Methods evaluation of spectra statistical errors Tracer Studies history of radiotracer concept theory and methodology use of substoichiometry applications biology and medicine general hematology imaging, positron emission tomography metabolic research radiopharmaceuticals respiratory physiology environmental studies hydrology, groundwaters industry material flow dynamics polymer stabilization technology semiconductors sewage, sludge flow rates Isotopic Dating Methods accelerator based general applications ion sources sample preparation techniques Related Topics synthetic elements exotic nuclei and their decays proton decay neutrino mass

A59 A60 A61 A5, A62 A63 A64 A65 A66 A67 A68-70

A71 A67, A72, A73 A74 A75-77 A78 A73, A79, A80 A81 A82 A83 A84 A32 A85 A86, A87 A88 A89 A90 A91 A92 A93 A94

X-rays in the analysis of T h ores activated with a Pu-Be isotopic neutron source. Cyclic activation analysis measurements through use of short- and medium-lived radionuclides have been applied to analyses of botanical and zoological reference materials (B12)and corrosion products in nuclear power reactor cooling water (B13). A number of papers have presented computational techniques for optimization of INAA parameters (B14-17)and several new compilations of cross section and decay data have B19). The advantages and problems associated appeared (B18, with the monoelemental standard approach in INAA have B20,B21,B121-127)and the need for been described (Bl7, more accurate minor element isotopic abundances in reactor NAA has been argued (B21). Publications relating to sources of potential error in NAA have been numerous during the review period. Cornelis and Hoste (B22)have summarized potential systematic errors in reactor NAA of biological materials. Errors due to material loss in oxygen flask decomposition of biological materials (B23),ashing of plant samples (B24), evaporation of halogenated hydrocarbons during irradiation in environmental analyses (B25), and even loss of sample weight during irradiation due to decomposition of a biological matrix, e.g., blood components (B26), have been considered. Potential interferences from fission products in the NAA of rocks high in U have been evaluated (B27,B28). A useful tabulation of major and minor y-ray interferences, including principal sum peaks, in the INAA of silicate rocks has been provided by Potts (B29), and a list of selected reliable analytical photopeaks is also included. Other related topics include a linear least squares correction procedure for residual dead-time losses (B30),errors due to ineffective postirradiation removal of self-absorption superficial impurities in metals analysis (B31), of induced y-ray radiation in bulk samples (B32), recoil and

NVCLEAR AND RADIOCHEMICAL ANALYSIS

Table 11. Selected Applications of Instrumental Thermal Neutron Activation Analysis' Archaeology bone ceramics, pottery, glasp coins sampling techniques statistics. data interpretation stone, minerals, clays, soils

837 838-46' 847 848 842,844,851 R49-53, 877

Environmental, Biological Studies atmospheric biological systems and standards and As-kte

Dsan fa Research in the Graduate Schmi He has also been Fulbright Research Felbw a1 lhe ln~tinutelor Advanced Studies of the Australln National Univerrw and a virling scholar at Arizona State Universny and FWda State Universtiy. His research interests include innovative approaches to hate element analyiical chemistry using nuclear methods. especianv as a w i M to resBarch pobbms in geochemisw. cosmochemktry. and studies of lhe reiatbnships of brain trace element imbalances to neurological diseases. B

Slerm W. Y a m k a prolespa In the Chemlsby Oepamnsot of the Univaony of Kentucky. He received h k B.S. Degree In chemism horn Me Universw of MIssoud at Columbia and his Ph.0. In nuclear chemlsby hom Purdue univsrsny (1973). Aner 2 years 01 postdoctoraI research at A r p m e National LabOtat-. h. Yatas joined Me facuny at lhe Univnrny of Kentucky in 1975. His research eWDrm have been primarihl h basic nuclear S P B ~ ~ O S C O P Yand nuclear omcture studies of defamed and bsnsnional nuclei. but he makes an occasbnal excurs~oninto applying acceleratwbased techniques lor elemental analysis

irradiation enhanced diffusion in the analysia of metals (B33), systematic errors and optimization of measurement conditions in the determination of the daughter activity when parent halflife is shorter than that of the daughter in decay chains (8341, and identification of sources of sampling error, together with suggestions for their minimization, in the analysis of biological materials (835). In addition, Potts and Twomey (836) have discussed the variation of energy resolution (fwhm) due to the proportion of overload pulses in NAA with a lowenergy photon spectrometer. Publications representing applications of INAA have been multitudinous over the review period. This attests to the continuing popularity of INAA, especially for problems that require accurate and precise multielemental analyses of bulk samples with complex matrices. A representative, hut not exhaustive, selection of applications for a broad range of scientific disciplines is presented in Table 11. The majority of these publications use INAA for multielemental determinations. 2. Reactor Epithermal Neutron Activation Analysis (ENAA). Publications based on the use of nonthermal reactor neutrons (Le., those not largely absorbed by use of Cd or B filters) have been grouped together in this section. Alfassi (8116) has discussed different types of ENAA and their relative advantages. Tian and Ehmann (8117) have proposed a new generalized advantage factor that better reflects the improvement of practical detection limits in ENAA. They have also tabulated fast neutron reaction interference factors in both thermal and epithermal NAA. The use of B in conjunction with Cd as a thermal neutron shield in ENAA is reported to lead to improved sensitivities for F, Y, Sn, Ba, Er, W, and Pt in rocks, and F, Br, Rb, Y, Mo, Pd, Sn, Sb, I, Ba, Nd, Sm, Gd, Er, Hf, W, Re, Pt, Au, Th, and U in biological materials (8118). The effect of epithermal neutron flux depression in the area of a Cd-shielded irradiation box and related changes in nuclear reactor reactivity have been investigated (SI 19). A semiempirical method to compensate for impurity-element shielding in samples of irregular geometry has been proposed for both thermal and resonance neutrons (8120). The use of Zr as a multiisotopic flux ratio

84,854-55.864 82, 8 3 . 812, 8115, 822, 856,857 water. suspended matter, sediments 8 3 , 813, fl58-61,8113 Forensics 862, 863, 878

Geochemistry fossil fuels and byprcducts lunar samples minerals and ore8 rocks

soils Industrial Materials Medical and Biological Studies aging studies amniotic fluid blood or blood components bone brain breast tissue denial calculus DNA drugs and medicinal plants gallstones hair and nails liver nutrition studies placenta sampling techniques urine

Other cigarettes cosmetics nuclear power coolants and fuel

86449, 8113, 8114, 8194 870 €311, 871-73 810, 827-29,B74,875 860,876-78 85,8 3 1 , 8 3 3 , 8 7 S 8 3 895, 8106 884,8109

826,885-89 890 891-95 896 897 898 89S102

8103 8104-106 8107 8108

8109

835,8115 86 B110 8111

813. 8 1 1 2

"Some studies combine l NAA and RNAA. monitor is described, and an optimal cooling time prior to counting the Zr monitor is calculated (8121). Epithermal reactor neutron shape factors and associated effective resonance energies have been examined with respect to the absolute (Le., k,) single comparator standardization method (8122-126), and 'best value" activation cross sections have been tabulated (8126-8127). Applications of ENAA have been relatively few during the current review period. Selected examples included determination of P in bones and AI and Si in pottery ( B I B ) , multielemental analyses of rocks (8129). TI in coal ash and environmental samples (B130),halogens in milk (81311, and successive thermal and epithermal NAA on the same samples to determine Na, Mg, AI, Si, and P (8132). 3. Prompt y Neutron Activition Analysis (PGNAA). Much of the early work in PGNAA involved the irradiation of relatively small samples in a stream of thermal neutrons extracted from a beam port of a high-flux nuclear reactor. Modulation of the neutron beam with cadmium choppers interfaced to an analysis system, unique y-ray shielding configurations, and coincidence techniques were used to minimize radiation interferences to the analytical prompt y-rays emitted following thermal-neutron capture events. In the last several years, emphasis has been given to decoupling PGNAA from the large fixed nuclear reactor facilities. A mobile low-power nuclear reactor providing a total neutron flux of 3.3 X 104 n cmd sd has been developed for partial-body in vivo determinations (8133). Mobile systems employing isotopic neutron sources have been described for the determination of in vivo total-body N in humans (8134, 8135). PGNAA has been used for in vivo determinations of Cd in kidney (8133, 8136) and an improved calibration technique ANALYTICAL CHEMISTRY, VOL. 58. NO. 5. APRIL 1988

51 R


for the in vivo determination of body nitrogen, hydrogen, and fat has been proposed by a group at Brookhaven National Laboratory (B137). Other applications using isotopic neutron sources for PGNAA include borehole analyses for Fe in ore prospecting (B138),multielement borehole analyses of coal (B139),and on-line multielement continuous analysis of coal (B140). Applications of conventional high-flux reactor PGNAA are reported for the determination of B in tissues with detection based on track-etching techniques (B141), 10 elements in human liver samples (B142),B in 35 international geochemical reference standards (B143),and major constituent elements in metallic archeological artifacts and coins (B144, B145). 4. Activation Analysis Using Accelerator-Produced Neutrons (FNAA). The field of fast neutron activiation analysis (FNAA) is still dominated by the use of 14-MeV neutrons generated by low-energy Cockroft-Walton accelerators via the T(d,nI4Henuclear reaction. Recently, researchers in the USSR (I31461 have reported development of a portable 14-MeV neutron generator using a laser-actuated acceleration tube based on the same nuclear reaction. It is claimed that this generator can be made small enough to use in the field for major element analyses of drill cores, muds, and rocks. A new intense 14-MeV neutron generator employing a cylindrical accelerator structure has been used to measure FNAA cross sections for a number of (n, n’y) reactions leading to isomeric states with half-lives less than 12 s, in addition to other activation cross sections (B147). Cyclic activation methods have been used to improve sensitivities when using low-output generators (B148)and for the determination of 0, N, P, and K in cotton fibers and seeds (B149). FNAA based on detection of characteristic x-rays, as well as y-rays, has been reported (B150). Elayi (B151)has examined parameters affecting precision in 14-MeV FNAA and Ahafia and Jiggins (B152) have considered the effects of sample mass and matrix composition on the yields of radionuclides produced by recoil protons, especially in the FNAA determination of N. The 75Asreaction cross section at 14-MeV has been measured as part of a study of the As contents of hair, nails, and liver samples (B153). In vivo total body N in rats has been measured with 14-MeV FNAA, yielding a precision of 1.5% RSD, which is superior to the precision of 2.8% RSD achieved by use of the Kjeldahl method on sacrificed rats (B154). Other applications of conventional 14-MeV FNAA include analyses of Gaulish silver alloy coins (B155), ancient iron artifacts from India (B156),and fossil fuels (B157, B158). Several FNAA methods for the determination of the organic oxygen content of coals have been evaluated (B158). Autoradiography with cellulose acetobutyrate detector plates has been used to detect protons from the 14N(n,p)14Creaction in the determination of N in steel (B159). Fast neutrons are also produced with cyclotrons by deuteron irradiation of Be or Mg targets. Studies of the spatial neutron flux distribution with a Be target, FNAA sensitivities, and interferences are reported for cyclotron-produced neutrons (B160,B161). Activities produced in 21 elements by activation with fast neutrons produced by 22-MeV deuteron bombardment of a Mg target have been tabulated (B162). Cyclotron-produced fast neutrons have been applied to the analyses of a variety of environmental samples (B161). A unique FNAA approach uses an electron accelerator (microtron) to generate bremsstrahlung radiation in a primary converter target, which in turn reacts with a second converter, such as Be, to generate energetic photoneutrons by the (7,n) reaction (B163). These fast neutrons may be used in FNAA, or they may be moderated in graphite or Lucite for conventional thermal neutron activation. The microtron y radiation may also be used for photon activation analysis (section B.6). Combinations of photon and neutron activation products using the mixed y-neutron flux from a microtron have been shown to be effective in analyses for rare-earth elements (B163)and for 18 elements in meteorites (B164).Future applications of this technique will probably be limited by the availability of microtrons to the analytical chemist. 5. Charged Particle Activation Analysis (CPAA). The analysis of thin layers is an obvious area for exploitation with CPAA. Two publications in this review period dealt specifically with the development of methodology in this area. Varkonyi (B165) describes the use of proton cyclotrons for thin-layer analyses to study corrosion and wear in industrial 52R

ANALYTICAL CHEMISTRY, VOL. 58, NO. 5 , APRIL 1986

machines and tools. Absattarov and Mukhammedov (B166) make use of secondary particle activation analysis to analyze foils or films of B4C, B203,SiOz, AlN, Mg, and AI. In this study they sandwiched their samples between LiF films and irradiated the package in a high-flux nuclear reactor for 2 min. The samples were activated by tritons generated by the 6Li(n,ol)Treaction and a number of elements with 2 = 1-15 were determined. Heavy-ion CPAA employing loB ions has been used for the determination of H in Ti and Pb-bronze at the 100 p m level (B167). In the same study it was s u g gested that activation might be useful in the trace determination of Li and 0, via the 6Li(10B,n)150,7Li(10B,2n)150, and 1sO(10B,ol)24Na nuclear reactions. Low-energy (5 MeV) proton activation with energy dispersive X-ray counting has been used to calculate thick-target yields and interference-free detection limits for 15 elements (B168). The latter publication also describes the use of a 5-MeV proton beam and autoradiography for elemental mapping of a Ga-doped Si sample. Bondarenko et al. (B169)report the determination of C, N, 0, F, Si, and AI by use of 3-MeV deuterons from a linear accelerator and also discuss the generation of neutrons for NAA by focusing the deuteron beam on a Be target. Proton-beam activation analysis and thick-target y-ray yields from 9.1-MeV proton-induced reactions have been studied by Kuz’menko et al. (BI 70). Absolute intensity values of the main emitted photon lines and analytical sensitivities are also tabulated for a variety of elements. Other tabulations of proton and deuteron CPAA detection limits have been given for elements with 2 I 42 (B171)and for those with 2 > 42 (B172). Recent applications of CPAA include analyses for Cd and Ti in human serum (BI 73), studies of x-irradiation-induced binding of stable l80by amino acids (B174),determinations of the protein content of cereals (B175),sulfur determinations in coal (B176),C in glasses (B177),and B in both A1 and A1 alloys (B178). The influence of secondary neutrons on the results of proton activation analysis for the determination of W in T a has been considered (BI 79). Multielement CPAA determinations have been reported in a wide variety of matrices including W metal (B180),cobalt metal (B181),Si single crystals (B182),indium phosphide samples (B183),and water samples (B184). 6. Instrumental Photon Activation Analysis (IPAA). The recent literature contains relatively few publications in the field of IPAA. The publications available indicate that linear and microtron types of electron accelerators are about equally used for current studies. Davydov and Magera (B185) have tabulated sensitivities (g/count) and lower limits of detection (g) for 28 elements by IPAA with detection of both soft y emission and X-rays. The same authors have also considered selective excitation of characteristic x radiation from an element of interest by X-rays emitted by neighboring elements activated by PGAA (B186). An example was presented based on the determination of I by counting I X-rays whose emission was induced by Ce X-rays resulting from the decay of 140Pr,which was in turn produced by the l4lPr(y,n)140Pr reaction. Another publication from the same laboratory in the USSR lists determinations of isomer ratios in yields of photonuclear reactions that may have utility in IPAA and compares them to literature values (B187). A new standardization method for IPAA has been proposed which takes into account sample self-absorption of low-energy y-rays and avoids the necessity of using the internal standard approach (B188). A modification of the internal standard method in IPAA is also described for samples in which elements suitable as internal standards are not present and self-shielding effects can be neglected (B189). The approach is based on the use of a comparative standard, which is prepared to contain a known ratio of the element to be determined and a suitable internal reference element. A known amount of the internal reference element is also added to the sample to be analyzed, both the comparative standard and the doped unknown sample are sequentially activated and a simple equation is used to calculate the concentration of the element of interest in the unknown. The method has been applied to the determination of Ti, Cr, Ni, and Zr in A1 alloys. In another study interference reactions and appropriate irradiation times have been studied in relation to multielement IPAA analyses of geological cores, meteorites, ores, and soils using a microtron (B190).


Table 111. Applications of Preconcentration or Radiochemical Separations in Activation Analysis elements determined

matrix

methodology/ points of interest

ref

Biology/Medicine various tissues

As As, Bi, Cd, Cr, Hg, Pb, Sb, Se, T1

As, Cd, Hg As, Cd, Cu, Mo Cu and others I Mn, Cu, Zn

rare earths Se and others Se, Ag, Au, Pt, and others Se, Hg, Fe, Co, Zn, Ag, Sn, Cr, Yb, Sb, Au, As Sn preconcentration amniotic fluid blood

multielement Mn, Cu, Zn, Fe

urine

Cu, Fe, Zn protein-bound I Se compounds

77Asas a yield tracer wet ashing procedure pollution effects solvent extr. + inorg. ion exch. resin reduction to Cu(1) + pptn ox.-red. rx + pptn CIB-bondedsilica gel F- pptn. chelating agents other HAP + anion/cation exch. pure Hg or Zn amalgam extn. S2- and OH- pptn. solvent extr. of SnI, use of diethyl dithiocarbamates Chelex 100 chromatography HAP extn. by HOAc-BuOH with a polytetrafluoroethylene porous membrane HAP + solvent extr. gel filtration molecular act. anal.

B202 B199 B217 B218 B235 B211 B203 B212 B213 B214 B220 B205 B219 B215 B216 B198 B84 B221 B222 B211 B6

Environment fish water

sediments

Mn, Zn, Cr, Ag Au, Cd, Cu, Mo, U, Zn As, Cd, Co, Cu, Hg, Mo, Sn, Sb, Te, Ti, U, V, W Ra, Rn, Pb, Th, Po

solvent extr. + pptn. C-fiber column electrolysis adsorption colloid flotation use of natural radionuclides as environmental tracers

B223 B204 B207 B224

Geology lllAg as a yield tracer

rocks and minerals Ag rare earths

ion exch., general

precipitation solvent extr. Te co-pptn using Sn2+as a reductant surfactant extraction in CHC13solns. modified fire-assay ko standard method

noble metals

multielement

B202 B225-228 B212, B226, B228, B230 B229, B230 B231 B232 B233 B209

Industry semiconductors

halogens Y

An interesting recent application of IPAA is the use of a 30-MV linear electron accelerator for the in vivo measurement of capillary blood flow in animal tumors using the photoactivation product radionuclide, 150(B191). Other applications include determination of the C content of coals by the lZC(B192),as well as multielement determi(~,n(r)~B reaction e nations in coal and coal ashes (B193,B194), phosphate ores (B195),soils (B196,B197), industrial materials (B79),rareearth metals (B163),and meteorites (B164). 7. Methods Based on Radiochemical Separations (RNAA). Publications that emphasize postirradiation chemical separations or sample preconcentration in activation analysis are reviewed in this section. Several new developments in methodology are specifically reviewed and representative applications in radiochemical neutron activation analysis (RNAA) or preconcentration are tabulated in Table 111. The loss of some elements in sample dissolution or subsequent chemical separations has always been a major concern in RNAA. Pietra et al. (B198)have considered the loss of selected elements in sample dissolution and preconcentration steps commonly used for the RNAA of biological samples. Freeze-drying, wet-ashing in a Teflon bomb, evaporation a t 60 “C, dry ashing, and chromatographic preconcentration are considered. An open, wet-decomposition procedure with yield recoveries of 93-100% has been developed for the determination of trace elements significant in biological processes

B234 extr. of mercuric halides bv a-nonylpyridine N-oxide and BuBP04

(B199). The method is based on the use of HNO,, HCl, and HzOzand has been used for determination of Hg, Se, and other elements in plant materials and human hair. The use of X-ray fluorescence analysis as an alternative to reactivation in the determination of recovery yields has been proposed (B200B201). The use of an 241Amsource for the XRF excitation has been demonstrated (B200). Another approach uses added radioactive tracers not produced in significant amounts by neutron capture reactions (e.g., 77Asand ll1Ag) for yield determinations in analyses of biological and geological samples (B202). Among the more innovative new separation schemes are the use of columns of CI8-bonded silica gel after sample complexation by 8-quinolinol, ammonium pyrrolidinecarbodithioate, or cupferron for postirradiation separation and determination of Mn, Cu, and Zn in biological materials (B203),qreirradiation electrolysis on a C-fiber column electrode to isolate Au, Cd, Cu, Mo, U, and Zn from seawater (B204),postirradiation sample extraction with pure Hg or a Zn amalgam as the first step in the separation of a group of elements (largely transition metals, including Au and Pt) from biological matrices (B205),use of thin films of iron(II1) hydroxide deposited on glass to preconcentrate solutions for RNAA (B206),preirradiation collection of small amounts of both cations and anions from water samples by adsorption colloid flotation with a combination collector (B207),and the use of “chelating agent loaded resins” prepared by the adANALYTICAL CHEMISTRY, VOL. 58, NO. 5, APRIL 1986

* 53R


Table IV. Selected Applications of Isotope Dilution Analysis

element or compound of interest

methodology

ref

General Ca, Zn, Ce os

Pb Ru Sb T1

stable-IDA, enriched isotope, IPAA detection subst.-IDA, extr. with dithizone and liq. scint. counting stable-IDA, thermal ioniz. mass spec. subst.-IDA, extr. with dithizone, ‘@Ruradioactive spike SSE-IDA, redox reaction Tl(II1) and Tl(I), SSE-IDA

CI CIO CII c12 c2 C13

Biology/Medicine Cd, Cu Sr

ascorbic acid co11agen various compds benzodiazepines anticholinergic drugs

stable-IDA, thermal ioniz. mass spec. stable-IDA, enriched @%r isotope, IPAA detection half-life in guinea pigs, radio-IDA quantitation of insol. tissue collagen, radio-IDA stable-IDA, amniotic fluid, MS-IDA RIA-RRA comparison RRA

C14 C15 C16 C17 C18-20 C8 c9

Environment Cd, Pb, T1 NO;

stable-IDA, environ. spec. bank, MS-IDA stable-IDA, mass spec., water, MS-IDA

U, Th

use of 236Uand z20Thand (Y spectrometry, rocks

c21

c22

Geology C23

Industry Hf Pu

u, Pu

Hf in Zr and Zircaloys, stable-IDA, enriched isotope, act. anal. detect. 238Putracer in irrad. nuclear fuel solns., (Y spectroscopy MS-IDA, nuclear fuel

sorption of a chelating agent on an anion exchange resin to preconcentrate chalcophile elements prior to irradiation (B208). The ko standard method has been applied to the RNAA of geological, environmental, and reference samples and is found to offer advantages of simplicity, versatility, and computer compatibility with a potential accuracy of better than 5 % (B209). A computer-controlled chemical separation system for RNAA has been recently described by Stout (B210). Addition of activable tracers (B1-4), derivative activation and molecular activation analysis (B6) are also analysis (B5), techniques that involve preirradiation chemical manipulation of the sample. However, they differ somewhat from the other preconcentration or group separation methods featured in this section. They are considered in section B.l of this review.

C. ISOTOPE DILUTION ANALYSIS (IDA) A relatively new approach to IDA involves the determination of elements that have at least two stable isotopes, which may be converted by activation analysis methods to radioactive isotopes whose activities may be readily detected. Use of the counting ratios of the y-rays emitted following activation by the two radionuclides produced in the sample and in the isotopic mixture, when coupled with data for the isotopic ratios for the natural element and in the isotopically enriched spike, atomic masses, and the amount of enriched isotope added, allows determination of the amount of the element of interest in the original sample. The method is well illustrated in a publication by Masumoto and Yagi ( C l ) for the determination of Ca, Zn, and Ce via IDA-photon activation analysis. Additional applications involving similar methodology are tabulated in Table IV. Sub- and superequivalence isotope dilution analysis (SSEIDA) has also received considerable attention during the review period. In this technique two series of solutions are required. Samples in the first series contain the same amount of sample and radioactive spike but are isotopically diluted by increasing amounts of stable carrier. The second series contains no added carrier, but each solution contains k (a single value of k can be used, or a set of k values for replicate analyses) times the amount of both sample and radioactive spike in the first series. With all solutions first brought to the same volume, a substoichiometric amount of reagent is added to each solution, the products are isolated, and a 54R


C24 C25 C26

graphical method based on measuring activity ratios in the two series vs. the increasing amount of carrier added in the first series is used to calculate the amount of the element in the original sample. A detailed description of the technique has been given by Yoshioka and Kambara (CB), and errors associated with the techniques have been discussed by Kyrs and Prikrylova (C3). Some applications are listed in Table IV. Other publications dealing with related methodology include substoichiometric isotope dilution analysis (subst.-IDA) with masking reagents and auxiliary extractants ( C 4 , a study of the theoretical accuracy of the least-squares method in IDA (C5), and a technique based on interphase distribution of activity using extraction from multiple volumes of analyzed solution (C6-C7). The techniques of radioimmunoassay (RIA) and radioreceptor assay (RRA) are also related to subst.-IDA. The applications of these latter techniques are manifold in the biochemical literature. A recent publication compares RIA and RRA for the meaurement of benzodiazepines in biological systems (C8). A discussion of the development of the field of RRA as related to the measurement of drugs in biological fluids has been given by Ensing and De Zeeuw (C9). The reader is referred to reviews listed in Table I for additional references to RIA and RRA. Examples of applications for both mass spectrometric (MS-IDA) and radiometric (radio-IDA) detection methods are given in Table IV.

D. RADIORELEASE, RADIOMETRIC TITRATION, AUTORADIOGRAPHY, DIRECT COUNTING OF NATURAL RADIONUCLIDES A book entitled “Emanation Thermal Analysis and Other

Radiometric Emanation Techniques” by Balek and Toelgyessy (A42) is a major contribution to this section, which features less common techniques. Unfortunately, the book is published in Hungarian, There are many potential applications of this technique, and we can hope that a translation will be forthcoming. A radiorelease method has been reported for the determination of SOzat concentrations of 1-40 ppm in gas mixtures by use of 36C1-labeledchloramine T (01). A radiometric titration of diethanolamine with “ZnS04 and the determination of mono- and diethanolamines in mixtures by a radiometric method are described by Varadan et al. (02).


Autoradiography coupled with activation analysis has been used to investigate doping and impurity element distributions in a variety of materials including Si wafers, quartz and LiNbOs (B16403).Direct natural sample counting utilizing an intrinsic Ge well-type detector has been used to determine the activities of U-series radionuclides in marine phosphate nodules ( 0 4 ) . The direct counting results compare favorably with those obtained by more time-consuming radiochemical techniques.

E. CHARGED-PARTICLE REACTION ANALYSIS The use of charged-particle beams for elemental analysis is a rapidly developing area. Here we have grouped three methods (PIGE, PIXE, and RBS) that employ small accelerators, usually a Van de Graaff accelerator or a small cyclotron, to bombard samples with positively charged particles. In many analyses more than one of these accelerator microanalytical techniques can be used simultaneously. Each of the three methods can similarly be utilized in nuclear microprobes, and these are the final subject of discussion in this section. 1. Particle-Induced ?-Ray Emission (PIGE). In PIGE analysis the prompt y-rays that are emitted following a charged-particle induced nuclear reaction are detected, usually with a solid-state photon detector or a large NaI(Tl) scintillator (for high-energy y-rays). Typically, a solid sample under vacuum is bombarded with a collimated and energy-analyzed particle beam. While protons are by far the most commonly used particle beams, heavier particles are useful in many applications. There seems to be no universally agreed upon acryonym for this technique which has also been called PIGME, PIPPS (particle-induced prompt photon spectroscopy), and GRALE (y-ray analysis of light elements). The latter acronym carries some additional information about the technique; it is usually applied to the lighter elements, because reactions with heavy elements require higher-energy particles with accompanying complexity in accelerators and detection problems. PIGE is particularly useful for detecting lighter elements that cannot be observed with X-ray fluorescence techniques and is capable of distinguishing between isotopes of an element. High-resolution depth profiling with low-energy nuclear resonances in proton-induced reactions has been demonstrated for the determination of concentration profiles of F, Ne, and Na in various materials (El). When used in conjunction with Rutherford backscattering (RBS), the nuclear resonance technique was shown to be a unique probe for the importance of chemical effects in implanted metals. Similarly, l9Fprojectiles were used to study the content and distribution with depth of hydrogen in amorphous hydrogenated silicon through the H(lgF,ay)l 0 reaction (E2). Relative thick-target yields for PIGE analysis on light elements have been measured for protons (E3)in the energy region 2.4 < Ep < 4.2 MeV, for 4He+ bombardments (E4) at 2.4 MeV, and for protons, deuterons, and CY particles at 8 MeV per nucleon (E5)to increase the data on the basis base for thick-target analyses. Kiss et al. (E6), of experimental relative thick-target PIGE yield curves, have treated the role of different (p,X) reactions exciting a given y transition and have shown that such ambiguities can be resolved by proper selection of bombarding energies when analyzing a complex matrix. The questions of accuracy and precision in thick-target PIGE-PIXE analysis have been addressed by Carlsson (E7)who found that the determined deviations from geological reference standards for several elements from Na to Sr were all 50) and the increased accessible depth of analysis. Mendenhall (E13)has employed 4-MeV C1 ions to look at heavy element (e.g, Pb or U) surface concentrations of 109/cm2 on light substrates and has used C, 0, and F backscattering for isotopic ratio measurements to determine the fractionation induced by ion beam sputtering. It was possible to separate one mass unit at mass 63 and, by careful fitting, determine isotopic ratios for systems around mass 100. Also, heavy-ion E14). RBS has been used to profile multilayer targets (E13, The high dE/dx of heavy-ion beams gives good depth resolution even for targets consisting entirely of heavy elements. It has been pointed out that the accuracy for determining elemental depth profiles with ‘Li is limited by the accuracy of Li ion stopping powers (E15). Aumayr et al. (E16) have made an analysis of the accuracy, which can be obtained in determining stopping cross sections from the width of RBS spectra. Evidence for distortions of RBS spectra caused by secondary electron neutralization of the incident beam has been presented (E17). The applicability of RBS has greatly expanded with the advent of external beams; 3-6 MeV protons and 10-MeV CY particles have been used for RBS depth profiling (E18).This new capability permits the analysis of objects that are too large or otherwise incompatible with an accelerator vacuum system Hemment et al. (E19) has performed RBS with continuous rotation of the sample for the accurate determination of relative doses of implanted impurities. Calibration of the scattering geometry from random measured spectra has been used in optimizing glancing angle RBS (E20). The lZCresonance at 4.26-MeV has been used to improve the sensitivity for carbon and to determine the depth distribution in thin films (E21). Weber and co-workers (E22) have measured the low-energy backgrounds in RBS spectra from various monoelemental thin foils with protons, a , and lZCprojectiles over a large energy ANALYTICAL CHEMISTRY, VOL. 58, NO. 5, APRIL 1986

55R


range and have determined that the measured backgrounds are only partly explained by the model of double scattering in the target. Doolittle (E23) has developed algorithms for the rapid simulation of RBS spectra, and a graphical method has been developed to relate RBS data to sample characteristics such as thickness and concentration profiles (E24). Novel applications of RBS include measuring corrosion layers on glasses for long-term storage of radioactive waste (E%,E26) and the nitrogen concentration in diamonds (E27). 4. Nuclear Microprobes. A nuclear microprobe is a device that uses nuclear reactions to analyze the surface of a large variety of target materials by scanning the chargedparticle beam across the surface. It is possible to use each of the methods discussed in this section in this mode and to attain sensitivities at the parts-per-million level for many elements. The generation of the tiny beam with micrometer dimeiisions is achieved by collimation with consecutive focusing of the projectiles. Several reviews of this methodology (A53-58) and descriptions of facilities (e.g., ref E28 and E29) are available. The measurement of trace element distributions across single human hairs (E30)is typical of the type of study that can be performed by using microbeams and a combination of techniques-PIXE and RBS in this example. With 1-pm beams, it is even possible to examine microcircuits using RBS (E31). While a microphoto can be used to determine the region of interest before scanning (E32), beam sizes approaching the submicrometer level make it desirable to employ secondary electron images, as is done in electron microprobes, for beam positioning, focusing, and locating features of interest (E31, E33). The emergence of three-dimensional profiling ( E 3 4 4 3 6 ) or “tomography” (E37) by RBS microprobe analysis is particularly noteworthy, since it illustrates the power of these methods and provides us with an entirely new set of research opportunities to ponder. Some additional applications for which the nuclear microprobe is capable of providing unique information include microelement profiles of individual blood E39), composition analysis of human atherosclerotic cells (E38, artery walls (E40), and the determination of magnesium isotopic ratios in chondrules of the Allende meteorite (E41).

F. TRANSMISSION, ATTENUATION, AND SCATTERING METHODS Transmission and attenuation methods are most commonly employed with uncharged species, such as neutrons or y-rays, while useful scattering processes occur with most nuclear radiations. These methods find particular utility in monitoring quantitative variations in flow processes and in quality control applications. Scattering processes not discussed previously are also considered here. 1. y-Ray Methods. Starchik et al. (FI)have used a method based on the scattering of y radiation to monitor the ash content during loading of coal onto railway cars. The ash content of coal has also been shown to be obtainable from a pair production technique (F2). In these measurements, the coal is irradiated with high-energy y-rays, and the resulting annihilation radiation and Compton-scattered y-rays are detected. Iron ores have been analyzed by a combination of neutron and y-ray irradiation followed by y-ray detection (F3). Palathingal (F4)has suggested the use of nuclear resonance fluorescence of the continuous spectrum of y-rays generated by Compton scattering with radioactive sources as a possible technique for materials analysis. Particle-size effects in y-ray absorptiometry have been considered (F5), and a particlesize-dependent attenuation law has been constructed. y-Ray attenuation has also been employed for monitoring the composition of flowing liquids (F6). 2. Neutron Methods. Bulk samples have been nondestructively analyzed through neutron attenuation measurements where an accelerator was used for neutron production and attenuations were measured by pulsed-beam time-of-flight techniques (F7). Average H, C, N, and 0 contents were deduced by comparing attenuations to those measured for pure elements and statistical precisions of 0.3-0.7 % were achieved. Neutron beam transmission using an isotopic source has been used to determine the amount of hydrogen in graphite and zirconium (F8), while actinides and fission products were determined in nuclear reactor fuel samples by neutron resonance transmission analysis (F9). 56R


3. &Particle Backscattering. The use of @-backscattering has diminished over the years as other methods have been developed, but it can be used effectively for specific purposes. Burek and Zurawicz (FIO)have examined the errors accompanying the scattering process resulting from variations of the chemical composition in the sample and have developed a prescription for optimizing concentration measurements in heterogeneous materials. Bachvarov et al. ( F I I ) report the developments of a P reflectometer for the determination of heavy and medium heavy elements which has a direct readout of the percentage concentration.

G. STANDARDS FOR ELEMENTAL ANALYSIS Many of the publications cited in sections B-F present data for elemental concentrations in standard reference materials. However, the literature cited in this section has as its primary concern the preparation and processing of elemental standard reference materials (SRMs) or the tabulation of new SRM concentration data. For the most part, we have included only publications that have applied one or more of the analytical methods reviewed in this paper. A few new standards with unique matrices that have only been analyzed, to date, by other techniques are also listed. Glascock (GI) has prepared a useful monograph that summarizes elemental abundance data for many commonly used NBS and USGS reference materials. His compilation also includes tables of neutron capture cross sections, isotopic abundances, atomic masses, y-ray energies, and branching ratios for use in NAA. Byrne has considered processing of standards as a source of error in NAA (G2),and Pushkin et al. (G3) discuss the calibration of standard substances by the comparator method. An internal standardization method based on the use of an element already present in the sample and a comparative standard prepared by applying the standard addition method to a duplicated sample aliquant has been described by Yagi and Masumoto (G4). Other selected publications relating to reference standards are tabulated in Table V.

H. WELL LOGGING Well logging, the remote analysis of boreholes, places special demands on nuclear analytical methods. In a typical application, a radiation source (an isotopic y-ray or neutron source, or a small accelerator) is placed in a borehole and the y-rays and/or neutrons produced by nuclear reactions or scattering are detected in detectors that must, by necessity, be located in close proximity to the radiation sources. Signals from the detectors are then transmitted via cables of considerable lengths to a recording station. A great variety of geological information about the borehole (e.g., salinity, porosity, mineral content) can then be deduced as a function of depth in the well. While much of the activity in this field is confined to industrial reports, the open literature (e.g., ref H1-H8) indicates that this is a well-developed field with considerable sophistication, not only in the experimental methods but also in the ability to interpret these data. The development of compact accelerators or neutron generators capable of producing the high fast neutron fluxes necessary is one of the fascinating aspects of well logging technology (H9-Hll). These accelerators, as well as the detectors used, must be capable of operation in various unsavory environments. Elemental analysis of geological formations is possible if a high-resolution y-ray detector is used in the logging tool. For this reason, the cryogenics necessary for maintaining the low-temperature operating environment of germanium detectors has received considerable attention (H12).

I. INSTRUMENTATION New nuclear analytical instrumentation often follows developments in other areas of science, such as nuclear physics, or involves extensions of existing technology. We will briefly examine some of the recent advances that have not been discussed in previous sections, although we must candidly admit that we have not uncovered any revolutional developments. Radiation sources are necessary for essentially all of the methods we have discussed. The compact, high-intensity proton linac that delivers 10 mA of beam on a thick Li target


Table V. Publications Relating to Elemental Reference Standards method of analysis

ref

samples/points of interest Biology/Environment/ Medicine

synthetic resin multielement stds. human liver, Nat. Environ. Spec. Bank (NESB) program Chinese biological SRM (peach leaves), monostandard technique, homogeneity tests Br and C1 in oils and other elements in various stds. USSR synthetic resin biostandards, INAA and XRF NBS Urban Air Particulate SRM 1648 synthetic std. (V1) for human hair anal. bovine serum SRM German Environ. Spec. Bank ref. materials NIES mussel environmental ref. material elemental losses in the ashing of NBS orchard leaves SRM RNAA wet open-mineralization of NBS and IAEA ref. stds. with scavenging by activated C milk powder (Ispra 2) certif. ref. material NBS citrus leaves, new bovine liver, wheat and rice flours, milk powder, and stabilized wine SRMs marine sediment and lobster hepatopancreas SRMs IPAA rare-earth elements in 37 international geochemical ref. materials PGNAA multiple techniques human liver, quality control, sampling, transport, storage of std. material, etc. freshwater angiosperm, freshwater moss, olive twigs natural certif. SRMs human placenta and urine ref. materials INAA

G5, G6 G7 G8-10 GI1 G12 G13 G14 G15 G16 G17 G18 G19 G20 G21 G22 G23 G24 G25 G26

Geology INAA/NAA

RNAA PGNAA

international standard rocks silicate std. rocks AN-G, BHVO-1, QLO-1, RGM-1, SDC-1 and STM-1 std. rocks SG-lA, SGD-1A and ST-1A Chinese geochemical SRMs: rocks GSR-1 to 3, soils GSS-1 to 8 and others Bulgarian aeostandards: monzonite BV, gabbro GV, dolomite DM, Cu ore MrA, fire clay OgG and sulfide ore OZrO NBS fly ash SRM 1633A, std. pottery SP, USGS BCR-1 NBS flv ash SRM 1633A NBS residual fuel oil SRMs 1619, 1620a, 1634a and 1634 Japanese std. rocks: granodiorite GSJ JG-1, basalt JB-1, andesite JA-1, rhyolite JR-1 and basalt JB-2 for rare earths NBS Fly Ash SRM 1633A B in geochemical reference stds.

G27 G28 G29 G30-32 G33 G34 G35 G36 G37 G35 B143

High-Purity Matrices NAA

multielement standards for NAA of high-purity substances

G38

Surface Analyses RBS

Bi-implanted Si specimens as ref. stds. Bi-implanted and-Ta vacuum-deposited stds.

to produce 2 x IO1’ n cmF2s-l described by Schriber et al. (11) appears to be quite interesting. They point out that the low associated y-ray yield results in the availability of good neutron beam quality for radiography and other purposes. Useful neutral intensity and energy distributions from protons in the energy range 2-5.5 MeV incident on thick lithium targets have been calculated (12). The use of zszCfisotopic neutron sources for neutron activation analysis has been explored by two groups (13, 14) with special emphasis on optimizing the moderation geometries. Sastri (15)has applied the (n,n’) and (y,y’) reactions with a 10-Ci zzeRasource for analysis of Sr, Cd, In, and Ba. The development of automated systems is important in reducing the drudgery of routine analysis. Two examples (16, 17) of such systems for activation analysis are noted. Salahi et al. (18)have reported a sample transport system with transfer times

Nuclear and radiochemical analysis - ACS Publications - American

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