Determination Of Isotopic Abundances Research Articles

Nondestructive determination of isotopic abundance using multi-energy nuclear resonance fluorescence driven by laser Compton scattering source

We report on the quantitative nondestructive analysis of the natural isotopic abundances of hafnium and tungsten elements using nuclear resonance fluorescence. Metallic samples of hafnium and tungsten were irradiated to six quasi-monochromatic γ-ray beams generated by laser Compton scattering in the energy range of 2.4–3.2 MeV. Multiple nuclei were simultaneously excited at each of the six γ-ray beam energies. A high-purity germanium detector array detected deexcitations of the nuclei. In total, 51 transitions were unprecedentedly employed to estimate the isotopic abundances of heavy elements nondestructively. The estimated abundances of three hafnium isotopes and three tungsten isotopes are consistent with standard known natural abundances within the experimental uncertainties. The deviation from the standard values ranges from 0.18% to 1.36%.

A study on the simultaneous determination of nitrogen content and 15N isotope abundance in plants using peak height intensities at m/z 28 and 29

A method for simultaneous determination of nitrogen content and 15N isotope abundance in plants was established by Elemental analysis-gas isotope ratio mass spectrometry. Taking poplar leaves and l-glutamic acid as standards, nitrogen content was determined using the standard curve established by weighted least squares regression between the mass of nitrogen element and the total peak height intensity at m/z 28 and 29. Then the 15N isotope abundance was calculated with the peak height intensity at m/z 28 and 29. Through the comparison of several sets of experiments, the impact of mass discrimination effect, tin capsule consumables, isotope memory effect, and the quality of nitrogen on the results were assessed. The results showed that with a weight of 1/x2, the standard curve has a coefficient of determination (R2) of 0.9996. Compared to the traditional Kjeldahl method, the measured nitrogen content deviated less than 0.2 %, and the standard deviation (SD) was less than 0.2 %. Compared to the sodium hypobromite method, the 15N isotopic abundances differed less than 0.2 atom%15N, and the SD was less than 0.2 atom% 15N. The established method offers the advantages of being fast, simple, accurate, and high throughput, providing a novel approach for the simultaneous determination of nitrogen content and 15N isotope abundance in plant samples.

Lithium Self-Diffusion in a Polymer Electrolyte for Solid-State Batteries: ToF-SIMS/ssNMR Correlative Characterization and Modeling Based on Lithium Isotopic Labeling.

Manufacturers aim to commercialize efficient and safe batteries by finding new strategies. Solid-state electrolytes can be seen as an opportunity to develop batteries with a high energy density. They allow the use of lithium foil as the anode, increasing the energy density. Also, they are composed of nonflammable materials making them safer than liquid electrolytes. However, to enhance the electrochemical performances of forthcoming solid-state lithium metal batteries, phenomena governing ionic conductivity have yet to be mastered in such devices. Lithium isotopic tracing was successfully used in previous works to further understand lithium ion transport mechanisms in batteries. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and 6/7Li high-resolution solid-state nuclear magnetic resonance (ssNMR) spectroscopy are two complementary techniques probing local and global scale, respectively. Both techniques can distinguish lithium isotopes. Here, four polymer membranes were elaborated with the same lithium concentration, but with various isotopic enrichments from 7.6 to 95.4% of 6Li. The selected material was a poly(ethylene oxide) (PEO) membrane containing lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) as lithium salt. They are widely studied in the lithium battery field. First, reliable ToF-SIMS and ssNMR methodologies were validated in light of the converging results. They led to accurate determination of lithium isotopic abundance of polymer membranes with a 1 or a 2% uncertainty, respectively. Then, the developed methodologies were applied to characterize lithium self-diffusion in a polymer membrane. Furthermore, numerical simulations based on a two-dimensional diffusion model compared with ToF-SIMS analyses allowed us to extract a lithium self-diffusion coefficient of 1.6 × 10-12 m2·s-1 at 60 °C, which complements other published values. The robust methodologies described in this work can be extended to various applications and materials. They stand as powerful strategies to better understand lithium ionic transport, especially in multiphase materials, for example, in hybrid solid-state electrolytes.

Determination of isotope abundance for deuterium-labeled compounds by quantitative 1 H NMR + 2 H NMR.

Deuterated reagents have been used in many research fields. Isotope abundance, as the feature parameter of deuterated reagents, the precise quantification, is of great importance. Based on quantitative nuclear magnetic resonance technology, a novel method that combines 1 H NMR + 2 H NMR was systematically established to determine the isotopic abundance of deuterated reagents. The results showed that the isotopic abundance of partially labeled and fully labeled compounds calculated by this new method was even more accurate than that calculated by classical 1 H NMR and mass spectrometry (MS) methods. In brief, this new method is a robust strategy for the determination of isotope abundance in large-scale deuterated reagents.

Soil carbon dynamics of no-till silage maize in ley systems

Converting grassland to arable cropping leads to reduced soil organic carbon (SOC) stocks and thereby affects soil and climate protection goals. However, in forage production systems, silage maize produces considerable amounts of herbage and metabolizable energy yields for ruminants. To answer the question whether using direct drilling, as a minimal soil invasive technique, is able to prevent SOC stock degradation without loss of herbage yield in ley-arable systems, a two-year field experiment was set up on a sandy loam soil in northern Germany. In pre-management, a 10-year-old grassland sward was eradicated with a glyphosate and then sown with silage maize with (i) direct drilling (no-till, NT); and (ii) by conventional mouldboard ploughing (conventional tillage, CT). Each treatment included a non-N-fertilized (N0) and a 90 kg N ha−1 year−1 fertilized (N1) treatment. All silage maize treatments were analyzed in terms of above- (ANPP) and belowground net primary production (BNPP) and potential C input in comparison with the grassland control (GC) during the two years after conversion to arable silage maize. Quantification of SOC stocks and origin of C derived from residual plant material was estimated by the determination of natural 13C isotope abundance. Long-term impacts on SOC of a proposed ley-arable system (three years of grassland followed by three years of silage maize) using NT and CT practices were predicted using a soil C model. Results showed that ANPP and BNPP did not differ (p > 0.05) between tillage treatments and the two experimental years. Fertilization increased ANPP only in the second year with a lower fraction of roots belowground in comparison with N0 (p < 0.05). According to the 13C signature the total of silage maize-derived C after two years was up to 2.5–3.2 t C ha−1 in both tillage treatments, of which ∼76% can be explained by the measured C inputs from plant residues. The NT treatment showed lower amounts of decay of previously sequestered C in the upper 10 cm during the two-year period after land use change to silage maize. However, long-term predictions revealed ongoing breakdown of soil C regardless of tillage management used for continuous silage maize after conversion from grassland. The insertion of a three-years grass phase followed by three years of silage maize established with NT techniques was able to maintain SOC stocks in the long-term.

Rapid Determination of Uranium Isotopic Abundance from Cotton Swipes: Direct Extraction via a Planar Surface Reader and Coupling to a Microplasma Ionization Source.

The collection of solid particulates and liquids from surfaces by the use of cloth swipes is fairly ubiquitous. In such methods, there is a continuous concern regarding the ability to locate and quantitatively sample the analyte species from the material. In this effort, we demonstrate the initial coupling of an Advion Plate Express plate reader to a liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma ionization source with an Orbitrap mass spectrometer to perform uranium isotopic analyses of solution residues on cotton swipes. The Plate Express employs a sampling probe head to engage and seal against the swipe surface. Subsequentially, the analyte residues are desorbed and transported within a 2% HNO3 electrolyte flow to the ionization source. Quantitative recoveries were observed following a single 30 s extraction step, with the absolute mass sampled per extraction being ∼100 ng. While the intrasample variability in the analytical responses for triplicate sampling of the same swipe yield ∼30% RSD, this lack of precision is offset by the ability to determine isotope ratios for enriched uranium specimens with a precision of better than 10% RSD. Pooled, intersample precision (n = 9) was found to be <5%RSD across the various sample compositions. Finally, 235U/238U determinations (ranging from 0.053 to 1.806) were accurate with errors of <10%, absolute. The 234U- and 236U-inclusive ratios were determined with similar accuracy in enriched samples. While the driving force for the effort is in the realm of nuclear nonproliferation efforts, the ubiquitous use of cloth swipes across many application areas could benefit from this convenient approach, including the use of versatile, reduced-format mass spectrometer systems.

Approach to quantitative spectroscopy of atomic vapor in optical nanocells.

We present a method for recovery of narrow homogeneous spectral features out of a broad inhomogeneous overlapped profile based on second-derivative processing of the absorption spectra of alkali metal atomic vapor nanocells. The method is shown to preserve the frequency positions and amplitudes of spectral transitions, thus being applicable for quantitative spectroscopy. The proposed technique was successfully applied and tested for measurements of hyperfine splitting and atomic transition probabilities, development of an atomic frequency reference, determination of isotopic abundance, study of atom-surface interaction, and determination of magnetic-field-induced modification of atomic transition frequency and probability. The obtained experimental results are fully consistent with theoretical modeling.

Spatially resolved carbon and oxygen isotopic ratios in NGC 253 using optically thin tracers

Context. One of the most important aspects of modern astrophysics is related to our understanding of the origin of elements and chemical evolution in the large variety of astronomical sources. Nuclear regions of galaxies undergo heavy processing of matter, and are therefore ideal targets to investigate matter cycles via determination of elemental and isotopic abundances. Aims. To trace chemical evolution in a prototypical starburst environment, we spatially resolve carbon and oxygen isotope ratios across the central molecular zone (CMZ; full size ∼600 pc) in the nearby starburst galaxy NGC 253. Methods. We imaged the emission of the optically thin isotopologues 13CO, C18O, C17O, 13C18O at a spatial resolution ∼50 pc, comparable to the typical size of giant molecular associations. Optical depth effects and contamination of 13C18O by C4H are discussed and accounted for to derive column densities. Results. This is the first extragalactic detection of the double isotopologue 13C18O. Derived isotopic ratios 12C/13C ∼ 21 ± 6, 16O/18O ∼ 130 ± 40, and 18O/17O ∼ 4.5 ± 0.8 differ from the generally adopted values in the nuclei of galaxies. Conclusions. The molecular clouds in the central region of NGC 253 show similar rare isotope enrichment to those within the CMZ of the Milky way. This enrichment is attributed to stellar nucleosynthesis. Measured isotopic ratios suggest an enhancement of 18O as compared to our Galactic centre, which we attribute to an extra 18O injection from massive stars. Our observations show evidence for mixing of distinct gas components with different degrees of processing. We observe an extra molecular component of highly processed gas on top of the already proposed less processed gas being transported to the central region of NGC 253. Such a multicomponent nature and optical depth effects may hinder the use of isotopic ratios based on a spatially unresolved line to infer the star formation history and/or initial stellar mass function properties galaxy nuclei.

Accurate Determination of Isotopic Abundance of Intracellular Metabolites of Saccharopolysporaerythraea Based on Ultra Performance Liquid Chromatography-Triple Quadrupole Mass Spectrometry

Abstract A method was established for measuring 13C isotopic abundance of intracellular metabolites of Saccharopolysporaerythraea by ultra-high performance liquid chromatography (UPLC)-triple quadrupole mass spectrometry. Under the optimized chromatographic conditions of UPLC, and the appropriate and unique tube lens voltage, collision energy and ion pair, one-to-one method, one-to-many method and SIM method were established for measuring 13C isotopic abundance based on the length of the parent and daughter ions carbon chains and whether the daughter ions contain 13C atoms. The three methods were then applied to measure naturally labeled intracellular metabolite standards and 13C labeled samples. According to the gap between the experimental value and the theoretical value, the best method was found for each metabolite of different characteristics. The results showed that one-to-one method was the most effective for measuring the metabolites of daughter ions not containing 13C atoms represented by sugar phosphates, one-to-many method was the best for measuring the metabolites of both parent and daughter ions containing 13C short carbon chains represented by carboxylic acids, SIM method could played a role in measuring the metabolites of both parent and daughter ions containing 13C long carbon chains represented by coenzyme A. These methods had a good measurement precision and could be applied to the measurement of Saccharopolysporaerythraea intracellular metabolites, which would contribute to consequent study of the metabolic mechanism and the efficient expression of erythromycin.

Determination of Isotopic Abundance of 13C/12C or 2H/1H and 18O/16O in Biofield Energy Treated 1-Chloro-3-Nitrobenzene (3-CNB) Using Gas Chromatography-Mass Spectrometry

Determination of Isotopic Abundance of 13C/12C or 2H/1H and 18O/16O in Biofield Energy Treated 1-Chloro-3-Nitrobenzene (3-CNB) Using Gas Chromatography-Mass Spectrometry

Orbitrap mass analyser for in situ characterisation of planetary environments: Performance evaluation of a laboratory prototype

For decades of space exploration, mass spectrometry has proven to be a reliable instrumentation for the characterisation of the nature and energy of ionic and neutral, atomic and molecular species in the interplanetary medium and upper planetary atmospheres. It has been used as well to analyse the chemical composition of planetary and small bodies environments. The chemical complexity of these environments calls for the need to develop a new generation of mass spectrometers with significantly increased mass resolving power. The recently developed OrbitrapTM mass analyser at ultra-high resolution shows promising adaptability to space instrumentation, offering improved performances for in situ measurements. In this article, we report on our project named “Cosmorbitrap” aiming at demonstrating the adaptability of the Orbitrap technology for in situ space exploration. We present the prototype that was developed in the laboratory for demonstration of both technical feasibility and analytical capabilities. A set of samples containing elements with masses ranging from 9 to 208u has been used to evaluate the performance of the analyser, in terms of mass resolving power (reaching 474,000 at m/z 9) and ability to discriminate between isobaric interferences, accuracy of mass measurement (below 15ppm) and determination of relative isotopic abundances (below 5%) of various samples. We observe a good agreement between the results obtained with the prototype and those of a commercial instrument. As the background pressure is a key parameter for in situ exploration of atmosphere planetary bodies, we study the effect of background gas on the performances of the Cosmorbitrap prototype, showing an upper limit for N2 in our set-up at 10−8mbar. The results demonstrate the strong potential to adapt this technology to space exploration.

Determining the isotopic abundance of a labeled compound by mass spectrometry and how correcting for natural abundance distribution using analogous data from the unlabeled compound leads to a systematic error.

When the isotopic abundance or specific activity of a labeled compound is determined by mass spectrometry (MS), it is necessary to correct the raw MS data to eliminate ion intensity contributions, which arise from the presence of heavy isotopes at natural abundance (e.g., a typical carbon compound contains ~1.1% (13) C per carbon atom). The most common approach is to employ a correction in which the mass-to-charge distribution of the corresponding unlabeled compound is used to subtract the natural abundance contributions from the raw mass-to-charge distribution pattern of the labeled compound. Following this correction, the residual intensities should be due to the presence of the newly introduced labeled atoms only. However, this will only be the case when the natural abundance mass isotopomer distribution of the unlabeled compound is the same as that of the labeled species. Although this may be a good approximation, it cannot be accurate in all cases. The implications of this approximation for the determination of isotopic abundance and specific activity have been examined in practice. Isotopically mixed stable-atom labeled valine batches were produced, and both these and [(14) C6 ]carbamazepine were analyzed by MS to determine the extent of the error introduced by the approach. Our studies revealed that significant errors are possible for small highly-labeled compounds, such as valine, under some circumstances. In the case with [(14) C6 ]carbamazepine, the errors introduced were minor but could be significant for (14) C-labeled compounds with particular isotopic distributions. This source of systematic error can be minimized, although not eliminated, by the selection of an appropriate isotopic correction pattern or by the use of a program that varies the natural abundance distribution throughout the correction.

Atomic weights of the elements 2013 (IUPAC Technical Report)

Abstract The biennial review of atomic-weight determinations and other cognate data has resulted in changes for the standard atomic weights of 19 elements. The standard atomic weights of four elements have been revised based on recent determinations of isotopic abundances in natural terrestrial materials: cadmium to 112.414(4) from 112.411(8), molybdenum to 95.95(1) from 95.96(2), selenium to 78.971(8) from 78.96(3), and thorium to 232.0377(4) from 232.038 06(2). The Commission on Isotopic Abundances and Atomic Weights (ciaaw.org) also revised the standard atomic weights of fifteen elements based on the 2012 Atomic Mass Evaluation: aluminium (aluminum) to 26.981 5385(7) from 26.981 5386(8), arsenic to 74.921 595(6) from 74.921 60(2), beryllium to 9.012 1831(5) from 9.012 182(3), caesium (cesium) to 132.905 451 96(6) from 132.905 4519(2), cobalt to 58.933 194(4) from 58.933 195(5), fluorine to 18.998 403 163(6) from 18.998 4032(5), gold to 196.966 569(5) from 196.966 569(4), holmium to 164.930 33(2) from 164.930 32(2), manganese to 54.938 044(3) from 54.938 045(5), niobium to 92.906 37(2) from 92.906 38(2), phosphorus to 30.973 761 998(5) from 30.973 762(2), praseodymium to 140.907 66(2) from 140.907 65(2), scandium to 44.955 908(5) from 44.955 912(6), thulium to 168.934 22(2) from 168.934 21(2), and yttrium to 88.905 84(2) from 88.905 85(2). The Commission also recommends the standard value for the natural terrestrial uranium isotope ratio, N(238U)/N(235U)=137.8(1).

Determination of Isotopic Abundance of 2H, 13C, 18O, and 37Cl in Biofield Energy Treated Dichlorophenol Isomers

Determination of Isotopic Abundance of 2H, 13C, 18O, and 37Cl in Biofield Energy Treated Dichlorophenol Isomers

Determination of germanium isotope abundances and specific activity in accelerator produced germanium-68

Germanium-68 was produced by irradiation of a gallium target at a linear accelerator and purified by a two-step process involving leaching followed by chromatography. Germanium isotope abundances and specific activities of purified 68Ge were determined by inductively coupled plasma mass spectrometry (Perkin Elmer ICP-MS ELAN DRC) and gamma spectroscopy. The germanium abundances were: 68Ge (29.7–60.9 %) 69Ge (<1 %), 70Ge (37.7–64 %), 72Ge (<10 %), 73Ge (0 %), 74Ge (<5 %), 76Ge (0 %) and the specific activities were 53.8–155.9 GBq/mg. The low quantification limits of ICP-MS allow the analysis of diluted gamma counting samples so a separate ICP sample does not have to be prepared.

A non-LTE spectral analysis of the3He and4He isotopes in the HgMn starκCancri

We present a pilot study on non-local thermodynamic equilibrium (NLTE) line-formation computations for the isotopes 3He and 4He in the mercury-manganese star kappa Cancri. The impact of NLTE effects on the determination of isotopic abundances and the vertical stratification of helium in the atmosphere is investigated. Modern NLTE line-formation computations were employed to analyse a high-resolution and high signal-to-noise ratio ESO-VLT/UVES spectrum of kap Cnc. The atmospheric parameters were determined from fitting the hydrogen Balmer lines and the spectral energy distribution. Multiple HeI lines were investigated, including HeI 4921A and 6678A, which show the widest isotopic splits. Half of the observed HeI lines in the spectrum of kap Cnc show significant NLTE strengthening, the effects are strongest in the red lines HeI 5875A and HeI 6678A. NLTE abundances from individual HeI lines are up to a factor of about 3 lower than LTE values. Helium is found to be stratified in the atmosphere of kap Cnc. While the LTE analysis indicates a step-like profile of the helium abundance, a gradual decrease with height is indicated by the NLTE analysis. A 3He/4He ratio of about 0.25-0.30 is found. With the available data it cannot be decided whether the two isotopes follow the same stratification profile, or not. This work implies that NLTE effects may be ubiquitous in the atmospheres of HgMn stars and may have a significant impact on abundance determinations and the interpretation of the vertical abundance stratification of elements.

MetaProSIP: automated inference of stable isotope incorporation rates in proteins for functional metaproteomics.

We propose a joint experimental and theoretical approach to the automated reconstruction of elemental fluxes in microbial communities. While stable isotope probing of proteins (protein-SIP) has been successfully applied to study interactions and elemental carbon and nitrogen fluxes, the volume and complexity of mass spectrometric data in protein-SIP experiments pose new challenges for data analysis. Together with a flexible experimental setup, the novel bioinformatics tool MetaProSIP offers an automated high-throughput solution for a wide range of (13)C or (15)N protein-SIP experiments with special emphasis on the analysis of metaproteomic experiments where differential labeling of organisms can occur. The information calculated in MetaProSIP includes the determination of multiple relative isotopic abundances, the labeling ratio between old and new synthesized proteins, and the shape of the isotopic distribution. These parameters define the metabolic capacities and dynamics within the investigated microbial culture. MetaProSIP features a high degree of reproducibility, reliability, and quality control reporting. The ability to embed into the OpenMS framework allows for flexible construction of custom-tailored workflows. Software and documentation are available under an open-source license at www.openms.de/MetaProSIP.

Accurate Determination of 13C Isotopic Abundance of Free Intracellular Amino acids with Low Concentration by GC-MS-Selective Ion Monitoring Method

Abstract 13 C isotopic abundance of intracellular free amino acid with a characteristic of fast-turnover can quickly reflect the changes in intracellular metabolic state. However, the concentration of intracellular free amino acid was low and the existed 13 C isotope detection method based on GC-MS could not satisfy the requirement with full scan mode. In this study, selected ion monitoring method with theoretically higher detection accuracy was used for the analysis of 13 C isotopic abundance of free intracellular amino acid. The fracture law of different amino acids was investigated by full scan mode, and also a characteristic fragment library for the 16 kinds of free intracellular amino acids was established. According to this characteristic fragment library, only the specific m / z signal was detected in the sample analysis, which realized the selected ion monitoring and improved the quality of signal. The results of amino acid standards indicated that, in comparison with the full scan mode, the signal-to-noise ratio ( S / N ), measurement precision and accuracy were improved by 17, 2 and 3.8 times, respectively. In the analysis of coenzyme Q 10 producing strains of samples, 13 C isotopic abundance of 8 kinds of free intracellular amino acids were successfully detected. This method was quite feasible for the detection of 13 C isotopic abundance of the intracellular free amino acids in cell metabolism research.

Determination of 235U isotopic abundance by fission-yield difference method

Based on neutron activation analysis, a new method was presented for the determination of uranium isotopic abundance, in which fast neutrons generated by T (d, n) 4He were used to induce fission in uranium samples. The exponential relation between different abundances of 235U and the average fission-yield ratios of specific fission products was employed in this method. Taking the fission-yield ratios of specific fission products, such as Y¯88Rb/Y¯107Rh, Y¯88Rb/Y¯135I, Y¯88Rb/Y¯104Tc and Y¯92Sr/Y¯104Tc as the subjects of research, the relation curves between the average yield ratios and the 235U isotopic abundance as well as the expressions (Y¯i/Y¯j=f(H0)) for the average yield ratio (Y¯i/Y¯j) as a function of the 235U isotopic abundance (H0) were obtained. To verify the precision and accuracy of this method, 5 tests using each working curve were conducted for simulated samples with a 235U abundance of 72.2%, and the relative standard deviation (RSD) of all tests was less than 2%. Compared to the γ energy spectrum method, the relative error of each measurement result was between 1.11% and 1.66%.

Nuclear uncertainties in the s-process simulation

The heavy elements in the Universe are formed during the s- and r-processes mainly in AGB stars and supernovae, respectively. Simulation of s- and r-nucleosynthesis critically depends on the neutron capture and weak decay rates for all the nuclei on the reaction chain. The present work analyzes systematically the neutron capture rates (cross sections) for the s-process nuclei, including ∼3000 rates on ∼200 nuclei. The network calculations for the constant temperature s-process have been performed using the different data sets selected as the nuclear inputs to investigate the uncertainties in the predicted s-abundances. We show that the available cross sections of neutron capture on many s-process nuclei still carry large uncertainties, which lead to low accuracy in the determination of s-process isotope abundances. We analyze the neutron capture cross section data for the same unique isobar nucleus accorded by year from previous work. Such an analysis indicates that the s-process has been studied for more than fifty years and there exist two research stages around 1976 and 2002, respectively. The needs and opportunities for future experiments and theoretical tools are highlighted to remove the existing shortcomings in the neutron capture rates.