Non-destructive activation analysis of some elements in stony meteorites by proton and bremsstrahlen irradiation

Proton activation was applied for the instrumental analysis of Fe, Ni, Ca, Ti and Cr in stony meteorites. Error sources are discussed, some results are reported, and a comparison is made between this method and photon activation.     

Determination of arsenic in refractory metals by radio-chemical charged-particle activation analysis

Arsenic is determined in tantalum and tungsten matrices via ⁷⁵As(p, n)⁷⁵Se and ⁷⁵As(d, 2n)⁷⁵Se reactions. Two ion-exchange procedures, with Dowex-1 columns, are described for the separation of the indicator radionuclides. Data on thick target yields for the ⁷⁵As(p, n)⁷⁵Se reaction are given. With 13-MeV proton or 15-MeV deuteron irradiation for 2 h at a current of 5 μA, the detection limit for arsenic is at the 10 μg kg^-1 level.     

Non-destructive activation analysis of trace impurities in germanium

A non-destructive activation analysis of trace impurities in germanium giving rise to long-lived γ-emitting isotopes is described. Hg, Sn, Cr, Sb, Sc, Zn and Co were determined by γ-spectrometry after irradiation with thermal neutrons (φ_th=10^l4n. cm^-2.sec^-1, irrad. time: 15 h, cooling period: ca. 30 days). The complex γ-spectrum was analysed by a combination of Covell's method and matrix calculus. The detection limits are approximately 2 p.p.b. of Hg, 7 p.p.b. of Cr, 200 p.p.b. of Sn, 1 p.p.b. of Sb, 10 p.p.b. of Zn, 0.2 p.p.b. of Co and 0.1 p.p.b. of Sc.     

Non-destructive neutron activation analysis of atmospheric pollutants

Concentration of elements in atmospheric particulate of urban areas has been determined by employing a Ge(Li) detector. In the first part of this study, a single area was selected and samples were collected on millipor filter during three seasons of the year and their results were compared. These results were also compared with the concentration of the same elements reported for other cities. We have concluded that in a dry climate at least two parameters are involved in seasonal changes of trace elements in the atmosphere. They are the rate of wet deposition and reduction of vertical diffusion of airborne particulates.     

Non-destructive multi-element photon activation analysis of river sediments

A large number of toxic elements, including Th and U, in Scheldt and NBS river sediments, have been determined non-destructively by high energy photon activation. The length of irradiation varies between 1.5 hours for short lived-nuclides and 7–18 hours for long lived-nuclides. The induced activities are measured using a single open-ended coaxial Ge(Li) detector and the photopeak integrations are calculated using the total peak area method and the Cutipie computer program after substraction of the intrinsic background of the detector from each spectrum (Angela program). The photonuclear reactions and the best detection limits for 36 elements are indicated.     

Non-destructive bone aluminum assay by neutron activation analysis

A non-destructive method based on instrumental neutron activation analysis (INAA) for the assay of aluminum in bone samples is described. The²⁸Al signal obtained upon neutron irradiation includes contributions from both the reaction²⁷Al(n,)²⁸Al and³¹P(n,)²⁸Al. The first reaction is with the thermal neutrons and the second one is with the fast neutrons. The contribution from the³¹P reaction is calculated from the fact that Ca/P ratio in bone mineral is constant and the amount of calcium can be measured from the thermal reaction⁴⁸Ca(n, )⁴⁹Ca. The aluminum values obtained by the INAA procedure agreed within 10% of those obtained by atomic absorption spectrophotometry. With this assay the levels of aluminum in normal bones (<70 g g^–1 apatite) cannot be determined reliably but higher aluminum levles in bone biopsies associated with Al toxicity, e.g. some patients with renal osteodystrophy, can be determined with a precision of ±10%.     

Non-destructive analysis of phosphorus by neutron activation analysis in biochemical products

A method of neutron activation analysis is described for the quantitative determination of phosporus in nucleic acids, nucleotides and glucose-6-phosphate in amounts of 0.1 to 200 μg, without any chemical separation. This technique may be usefully applied to the measurement of the phosporus content in organic materials and biochemical preparations. The procedure involves a short neutron activation in a nuclear reactor and measurement of the Cerenkov radiation emitted by the irradiated capsule after a suitable decay period. Possible interferences due to other induced radionuclides are discussed.     

Non-destructive neutron activation analysis of the Naragh meteorite

The concentration of 18 elements in the Naragh meteorite that fell in Iran on August 18, 1974, has been measured by neutron activation analysis employing a high resolution Ge(Li) detector.     

Multi-reaction proton activation analysis for traces of molybdenum

The application of proton activation analysis to the determination of molybdenum is described. Thick molybdenum targets were bombarded with 12-MeV and 15-MeV protons. The reactions studied were ⁹²Mo(p,n)⁹² Tc, ⁹⁴Mo(p,n)^94gTc + ⁹⁵Mo(p,2n)^94gTc, ⁹⁵Mo(p,n)^95m Tc + ⁹⁶Mo(p,2n)^95mTc, ⁹⁵Mo(p,n)^95g Tc + ⁹⁶Mo(p,2n)^95gTc, ⁹⁶Mo(p,n)^96gTc+⁹⁷Mo(p,2n)^96gTc and ¹⁰⁰Mo(p,n)^99m Tc. Except for the Mo + p→^905mTc reaction, all these reactions give high analytical sensitivities. For 12-MeV protons and an irradiation time of one half-life or a maximum of 2 h, the sensitivities range from 5 · 10² to 6· 10³ d.p.m./p.p.m. μA, and for 15-MeV protons and the same irradiation conditions from 10³ to 10⁴ d.p.m./p.p.m. μA. In addition to the high sensitivity, the great advantage of proton activation is that different principal reactions yield indicator radionuclides with half-lives between 4.4 min and 61 d. Simultaneous determinations by these reactions are of value for checking the accuracy. For each reaction, detailed data are given on nuclear and instrumental interferences. Analytical application of this multi-reaction proton activation analysis is illustrated by the instrumental determination of molybdenum in cobalt.     

Non-destructive determination of dysprosium in graphites by neutron activation analysis

Natural graphites, graphite components, spectral and reactor grade graphites have been analyzed non-destructively for dysprosium by neutron activation and γ-spectrometry using^165m Dy (1.2 min) and¹⁶⁵Dy (2.3 hr). In four samples the determined Dy content was in the range 1.48 to 0.039 ppm. The deviation was ±18%. The limit of lower detection of the applied method amounts to 0.01 μg Dy, depending on the background contributed by other impurities.     

Optimisation of plasma techniques for trace analysis of refractory metals

Besides atomic absorption spectrometry, the plasma techniques can be seen as state-of-the-art instrumentation in an industrial laboratory for the analysis of trace elements today. For the analysis of refractory metals, e.g. Mo and W, the determination limits which can be reached by ICP-AES techniques are mainly restricted by the spectral background of the matrix. Advantages and disadvantages of sequential and simultaneous detection as well as different methods of evaluation, such as Kaiman filtering and multiple component spectral fitting, are discussed. The results are compared with trace matrix separation techniques and on-line coupling of ion chromatography with ICP-AES and ICP-MS. Furthermore, the limitations of all techniques with respect to their applicability for routine analysis, especially the complexity of sample preparation, degree of automation, time consumption and cost are shown. With respect to the detection capability, TMS with ICP-MS end determination is the most powerful technique, but for routine analysis simultaneous multielement determination from the matrix is favourable.     

Neutron activation analysis of refractory compounds

Instrumental neutron activation techniques for the determination of 26–36 impurities in MoSi₂, WSi₂, TiB₂, NbB₂, TiC, NbC and SiC with detection limit of 0.1–0.000001 ppm in the range of contents of 100–0.001 ppm have been developed. The determination of this large number of elements was achieved with using complex conditions of irradiation, including varying neutron energy and choosing optimal time parameters. The contents of short-lived radionuclides also have been determined. Self-shielding and disturbance of neutron flux, absorption of -rays were taken into account both with the help of literature data and preliminarily obtained experimental results.     

Two-energy proton activation analysis to determine simultaneously the trace elements of nitrogen and boron in gallium phosphide

The method of two-energy proton activation analysis was used to determine the concentrations of nitrogen and boron in gallium phosphide simultaneously. The sensitivity and precision of this method are discussed. In order to achieve the best results in determining the concentrations of nitrogen and boron at the same time, the concentration ratio of nitrogen to boron should be within the relative thick yields of boron to nitrogen at these two incident proton energies.     

Non-destructive examination of roman silver coins by neutron activation analysis

The detection of “plated” specimens (ancient falsifications consisting of a copper core with a silver outer layer) amidst a great collection of silver coins was performed by non-destructive neutron analysis. The “plating” can be detected by measuring the Ag/Cu ratio. In practice it is more convenient to determine the Au/Cu ratio which is proportional to it, A short activation in a low thermal neutron flux is sufficient for this purpose. Consequently the induced activity of the long-lived^110mAg is small. The necessary correction for self-absorption on the measured ratio is small. A series of 2000 coins was analysed in this way.     

Multi-element analysis of blood for trace metals by neutron activation analysis

Fourteen elements can be rapidly determined in whole blood by the neutron activation analysis procedure described. Three of these (Ag, Cl, Se) are measured after a 10-s irradiation and eleven others (Al, Ba, Br, Ca, Cu, I, Mg, Mn, Mo, Rb, V) are determined by a 180-s irradiation of a 1-cm³ sample of whole blood after destruction of organic matter and removal of sodium by hydrated antimony pentoxide. A further 13 elements (As, Au, Co, Cr, Cs, Fe, Hg, K, Na, Ni, Sb, Sc, Zn) are determined after overnight irradiation in the SLOWPOKE reactor.     

Non-destructive analysis of inorganic impurities in Brazilian coals by epithermal neutron activation

Twenty-two elements were identified and determined in different Brazilian coal samples by an epithermal neutron activation technique developed by the authors. The detection limits and the uncertainties of the results show that the technique can be used for routine analysis. The analysis of the complex gamma-ray spectra and the evaluation of the interfering activities are discussed in detail.     

Non-destructive determination of rhodium in platinum by epithermal reactor neutron activation analysis

Activation in connection with Ge(Li) γ-spectrometry proves profitable in determining traces of rhodium (and silver) in pure platinum. As the 556 keV photopeak of¹⁰⁴Rh was chosen for evaluation, its decay behaviour had to be considered. Moreover, a special automatic correction of dead-time and decay was applied. The limit of detection in a single run was 5 ppm.     

Non-destructive determination of aluminum in biological reference samples using neutron activation analysis

The non-destructive methods of thermal and epithermal neutron activation analysis have been employed to determine the aluminum concentration of seven National Institute of Standards and Technology certified biological reference materials. Through the judicious use of both thermal and epithermal neutron activation analysis using bare and boron-lined irradiation carriers, the major and minor contributions of the³¹P/n, /²⁸Al and of the²⁸Si/n, p/²⁸Al reactions, respectively, to the²⁷Al/n, /²⁸Al reaction could be corrected for explicitly. Based on replicate determinations precision of the analysis ranged from 2.5% for citrus leaves determined at the 75 ppm level to 18% for bovine liver measured at the 1 ppm level. Accuracy was demonstrated whenever possible by comparison to existing published data.     

Non-destructive determination of trace elements in tungsten by helium-3 activation analysis

A non-destructive method is described for the determination of trace impurities at sub-p.p.m. levels in a tungsten matrix by 14-MeV ³He activation analysis. A Ge(Li) spectrometer and a multichannel analyzer were used to determine V, Fe, Ni, Zn and Mo impurities. Interfering reactions are discussed in detail.     

Neutron activation analysis of noble metals in vegetation

Detection limits are presented for the platinum metals in vegetation for different neutron activation analysis conditions, namely, short irradiation, cyclic and long irradiations both thermally and epithermally. These detection limits for instrumental neutron activation analysis are compared with those using preconcentration technique—dry ashing and fire assay and post irradiation separation of the platinum metals using Srafion NMRR in exchange resin. The results are evaluated for plant material and it is concluded that dry ashing followed by cyclic, epithermal irradiation for rhodium and palladium and long, thermal irradiations for osmium, platinum, iridium and ruthenium enable these elements to be detected in plants at background levels.