High-sensitivity measurement of metastable ion abundances

Measurement of metastable ion abundances over a dynamic range of 10⁵ is possible with a specially designed mass spectrometer.     

Uranium and thorium abundances in chondritic meteorites

Neutron-activation analyses for uranium and thorium are reported for 42 chondrite meteorite "falls" and 1 "find" covering 15 of the 20 Van Schmus-Wood chondrite types. The mean uranium and thorium abundances of the 5 chemical groups show a trend with C group (U = 0.012(0) atoms/10(6) Si atoms, Th = 0.045(4) atoms/10(6) Si atoms, Th U = 3.7(8)) > H, L and LL groups (U = 0.008(3), Th = 0.028(0), Th U = 3.4(5)) > E group (U = 0.005(9), Th = 0.021(8), Th U = 3.6(9)). With the possible exception of the C3 chondrites, the mean abundances for each petrologic type within a given chemical group are identical.     

Bodily variability of zinc natural isotope abundances in sheep

Evidence is growing that the range of zinc stable isotope compositions, represented by the deviation of ⁶⁶Zn in permil units relative to a standard and expressed as δ⁶⁶Zn, is larger in organic matter than in inorganic material. This study reports the variations of δ⁶⁶Zn in various organs of sheep raised on a controlled diet. Zinc was purified by anion‐exchange chromatography. The Zn concentrations and Zn stable isotope compositions were determined by quadrupole inductively coupled plasma mass spectrometry and multi‐collector inductively coupled plasma mass spectrometry, respectively. The data show that δ⁶⁶Zn variability exceeds 1‰, with bone, muscle, serum and urine enriched in the heavy isotopes, and feces, red blood cells, kidney and liver enriched in light isotopes, all relative to the diet value. The ⁶⁶Zn enrichment of the circulating serum reservoir is likely to take place in the digestive tract, probably through the preferential binding of lighter isotopes with phytic acid, which is known to control the uptake of metallic elements. Mass balance calculations suggest that the ⁶⁶Zn depletion between diet and feces, which is not balanced by any other outward flux, leads to a secular isotopic drift in serum. A simple time‐dependent two‐box model, involving the gastro‐intestinal tract on the one hand and the muscle and bone on the other, predicts that the maximum ⁶⁶Zn enrichment, which equals the difference in δ⁶⁶Zn between diet and bulk (～0.25‰), is reached after about ten years. Therefore, a better understanding of the variations of natural abundance of Zn isotopes in animals and humans will probably bring new perspectives for the assessment of their Zn status. Copyright © 2010 John Wiley & Sons, Ltd.     

Elemental abundances of lunar soils by neutron activation analysis

Résumé Pour déterminer 44 éléments dans des échantillons lunaires on a fait appel à l'analyse instrumentale par activation neutronique et à l'analyse par activation neutronique utilisant des séparations chimiques et la spectrométrie gamma à haute résolution. Si on utilise ces méthodes conjointement à la spectrométrie de masse à étincelle, on détermine plus de 56 éléments avec une certitude moyenne de 10%. On compare les résultats de l'analyse de sols lunaires rapportés par Apollo 11, 12, 14, 15 et 16 et par Luna 16.      

The half-life and abundances of the gamma-rays of bismuth-207

The half-life of²⁰⁷Bi has been redetermined as 32.7±0.8 years. A new set of gamma-ray abundances are aslo calculated.     

Factors determining relative ionic abundances in competing fragmentation reactions

For the competing fragmentation reactions [la] and [Ib], it is shown that the relative abundances of [R₁]⁺ and [R₁]⁺ are determined by the relative values of the ionization potentials of the corresponding free radicals R₁^. and R₂^. In most cases the appearance potentials of [R]⁺ from RH follow the trends shown by the radical ionization potentials with the result that the appearance potentials can be used to correlate relative ionic abundances. The potential usefulness of relative abundances to estimate radical ionization potentials is illustrated.     

Precise determination of low isotopic nitrogen-15 abundances by emission spectrometry

Improvements in the determination of low nitrogen-15 abundances by emission spectrometry are described. Stronger emission is observed if a capillary constriction is formed at the centre of the discharge tube, and the background under the ¹⁴N¹⁵N peak is greatly reduced. The relative error normally caused by problems in estimating the background is thus decreased. The overall precision is better than 1% in the range from natural abundance to 1.0 atom-% nitrogen-15.     

Rare earth element abundances and distribution patterns in plant materials

Eight out of the fourteen rare earth elements were estimated from the leaves ofPelthophorum pterocarpum, the leaves and roots ofImpatiens balsamina, and the soils from four sampling sites by instrumental neutron activation analysis. The chondrite normalized rare earth element abundances and distribution patterns in the plant materials were found to be significantly correlated to the abundances of the rare earth elements occurring in the soils. The extent of accumulation of the rare earth elements in some plant materials was also govemed by the age of the plants and the plant organs.     

Substituent effects on ion abundances and energetics in substituted acetophenones

Based on the quasi-equilibrium theory of mass spectra it is shown that the intensity ratio [A]⁺/[M]⁺, where [A]⁺ is a fragment ion and [M]⁺ is the molecular ion, is given by [A]⁺/[M]⁺ = f′ (k₁/k_t) ((1/f) ? 1), where f is the fraction of molecular ions with insufficient energy to fragment, f′ is the fraction of [A]⁺ ions with insufficient energy to fragment, and k₁/k_t is the fraction of fragmenting molecular ions which form [A]⁺. For substituted acetophenones it is shown that f depends on the substituent present and that f′ k₁/k_t is also substituent dependent for formation of both [CH₃CO]⁺ and [YC₆H₄CO]⁺. It is also shown that no direct information concerning the effect of a substituent on the rate of a particular fragmentation reaction can be obtained from intensity studies. The ionization potentials of the parent molecules and the appearance potentials of the [YC₆H₄CO]⁺ fragment ions have been measured for fifteen substituted acetophenones and the correlations with substituent constants are discussed.     

Backscattering techniques for the measurement of stable isotope abundances and tracers

Prompt ion beam analysis methods can be used to measure the isotopic composition of materials. When applied using microbeams of charged particles they have the potential to measure the spatial distribution of isotopes. The value of Rutherford backscattering for isotope measurement is examined both from the point of view of the measurement of stable isotope abundances and the spatial distribution of stable isotope tracers. Parametes which affect the mass resolution and sensitivity are examined including incident particle energy and mass, scattering angle, energy spread of the incident beam, detector resolution and solid angle effects. Experimental measurement of the isotopic abundances of several elements are presented including magnesium, nickel and silver. A variety of incident ions and energies and different detection systems are used. The limitations of the method are discussed and its extension to nuclear microprobe application, with its spatial tracer determination capabilities, is appraised.     

Characterization of uranium isotopic abundances in depleted uranium metal assay standard 115

Certified reference material (CRM) 115, Uranium (Depleted) Metal (Uranium Assay Standard), was analyzed using a TRITON Thermal Ionization Mass Spectrometer to characterize the uranium isotope-amount ratios. The certified ²³⁵U/²³⁸U “major” isotope-amount ratio of 0.0020337 (12) in CRM 115 was determined using the total evaporation (TE) and the modified total evaporation (MTE) analytical techniques. In the MTE method, the total evaporation process is interrupted on a regular basis to allow correction of background from peak tailing, internal calibration of the secondary electron multiplier detector versus the Faraday cups, peak-centering, and ion source re-focusing. For the “minor” ²³⁴U/²³⁸U and ²³⁶U/²³⁸U isotope-amount ratio measurements using MTE, precision and accuracy comparable to conventional analyses are achieved, without compromising the quality of the ²³⁵U/²³⁸U isotope-amount ratios. Characterized values of the ²³⁴U/²³⁸U and ²³⁶U/²³⁸U isotope-amount ratios in CRM 115 are 0.000007545 (10) and 0.000032213 (84), respectively. The ²³³U/²³⁸U isotope-amount ratio in CRM 115 is estimated to be <5 × 10^?9. The homogeneity of the CRM 115 materials is established through the absence of any statistically significant unit-to-unit variation in the uranium isotope-amount ratios. The measurements leading to the certification of uranium isotope-amount ratios are discussed.     

Quantitation of ion abundances in fourier transform ion cyclotron resonance mass spectrometry

To improve the analytical usefulness of Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), an extensive survey of various methods for quantitation of peak magnitudes has been undertaken using a series of simulated transient response signals with varying signal-to-noise ratio. Both peak height (five methods) and peak area (four methods) were explored for a range of conditions to determine the optimum methodology for quantitation. Variables included dataset size, apodization function, damping constant, and zero filling. Based on the results obtained, recommended procedures for optimal quantitation include: apodization using a function appropriate for the peak height ratios observed in the spectrum (i.e., Hanning for ratios of about 1:10, three-term Blackman-Harris for ratios of ～1:100, or Kaiser-Bessel for ratios of ～1:1000); zero filling until the peaks of interest are represented by 10–15 points (generally obtained with one order of zero filling); and use of the polynomial y=(ax ²+bx+c) ⁿ and the three data points of highest intensity of the peak to locate the peak maximum, Y _max=(?b ²/4a+c) ⁿ . In this peak fitting procedure, which we have termed the “Comisarow method,” n is 5.5, 9.5, and 12.5 for the Hanning, three-term Blackman-Harris, and Kaiser-Bessel apodization functions, respectively. Accuracy of quantitation using an optimal peak height determination is about equal to that for peak area measurements. These recommendations were found to be valid when tested with real FTICR-MS spectra of xenon isotopes.     

Two-photon resonant three-photon ionization of Be applied to the determination of isotopic abundances

We show that when more than one photons are involved in bound-bound transitions by a broad-band laser for the determination of isotopic abundances, the ac Stark shift may cause the discrimination on ionization between different isotopes for a given atomic species. As an example, we present specific numerical calculations with Be atom in terms of the determination of isotopic abundances.     

Variations of natural 15N abundances in the tissues and digesta of domestic animals

The natural abundance of 15N (expressed as delta 15N per mil relative to air N2) in the tissues and the change of 15N abundance during the digestion processess in cattle, pig, and goat were investigated. The 15N abundances of cattle tissues differed by about 3.5% with high values in heart, urinary bladder and diaphragm. The ages of cattle did not affect on the 15N abundances of liver and kidney in cattle. The 15N abundances of urine were lower, and those of feces were a little higher than the values of diets in cattle and pigs. The delta 15N values of milk and blood were higher than the value of diets. Two peaks of 15N abundances at forestomach and caecum were observed during the digestion processes of diet in goats. The mechanisms of the variation of 15N abundances in animal bodies were briefly discussed.     

Elemental abundances in nature — Fortuity or conformity to natural laws?

Nuclear analytical methods during the last decades have given a lot of new data on elemental composition of various natural materials. These data allow a return to the question of the regularities of elements abundance. This question seems to be important from the point of view of basic science as well as analytical chemistry (analytical procedure planning, expected element concentrations, choice of sufficient sensitivity and reproducibility, etc.). The most fruitful approach in this connection is the comparison of the elemental composition of some generalized systems with an element's fundamental characteristics and/or its position in the Periodical System. Stronger correlations can be found when the elemental characteristic (its position in the Periodic Table) versus abundance is considered within separate groups of elements. This idea is illustrated by considering elements' abundance in the Universe, Solar System, Earth crust, sea water, soils, plants, etc. Simple equations describe these functions with acceptable agreement of tabular and calculated data. The coefficients of these equations in many cases were also connected with some fundamental characteristics such as ionization potential, ion potential, melting and boiling point, etc.     

High precision elemental abundances for tektites and crater glasses-thorium,uranium and potassium

Thorium, uranium and potassium mean abundances for 15 Ivory Coast tektites, 23 Australites, 10 Philippinites, 25 Thailandites, 16 Bediasites and 12 Moldavites are reported. Abundances are also reported for Muong Nong type tektites, Nordlinger Ries crater glass, Bosumtwi crater glass and Darwin crater glass. Previous measurements are reviewed. The value of the present work lies in the fact that high precision instrumental neutron activation analysis was employed to measure a large number of tektites encompassing the major strewn fields. Four independent measurements of thorium were made for each specimen with two Ge(Li) gamma spectrometers. Two of the measurements were based on the 312 keV gamma of²³³Pa, while the other two measurements were based on the uranium and X-rays which accompany the decay of²³³Pa. Internal consistency among the four thorium measurements is high. The uranium measurements were based on the 106 keV gamma of²³⁹Np, while potassium was measured from the 1524 keV gamma of⁴²K.     

The use of lead isotopic abundances in trace uranium samples for nuclear forensics analysis

Secondary ion mass spectrometry (SIMS), secondary electron microscopy (SEM) and X-ray analysis have been applied to the measurement of U-bearing particles with the intent of gleaning information concerning their history and/or origin. The lead isotopic abundances are definitive indicators that U-bearing particles have come from an ore-body, even if they have undergone chemical processing. SEM images and X-ray analysis can add further information to the study that may allude to the extent of chemical processing. The presence of “common” lead that does not exhibit a radiogenic signature is clear evidence of anthropogenic origin.