Relative Isotopic Abundances Research Articles

Protein Degradation Rate in Arabidopsis thaliana Leaf Growth and Development.

We applied 15N labeling approaches to leaves of the Arabidopsis thaliana rosette to characterize their protein degradation rate and understand its determinants. The progressive labeling of new peptides with 15N and measuring the decrease in the abundance of >60,000 existing peptides over time allowed us to define the degradation rate of 1228 proteins in vivo. We show that Arabidopsis protein half-lives vary from several hours to several months based on the exponential constant of the decay rate for each protein. This rate was calculated from the relative isotope abundance of each peptide and the fold change in protein abundance during growth. Protein complex membership and specific protein domains were found to be strong predictors of degradation rate, while N-end amino acid, hydrophobicity, or aggregation propensity of proteins were not. We discovered rapidly degrading subunits in a variety of protein complexes in plastids and identified the set of plant proteins whose degradation rate changed in different leaves of the rosette and correlated with leaf growth rate. From this information, we have calculated the protein turnover energy costs in different leaves and their key determinants within the proteome.

Using Radiogenic Noble Gases to Trace the Conditions of Crustal Fluid Migration

The radiogenic noble gas isotope composition (e.g., 4He*, 21Ne*, 40Ar*, where * denotes the radiogenic component) of crustal mineral grains was investigated to evaluate their utility as a geochemical tracer for characterizing subsurface processes and conditions of crustal fluid migration, specifically within black shales. Because the production of radiogenic noble gases can be predicted by measuring the relative abundance of parent isotopes (e.g., U, Th, K), the distribution of radiogenic noble gases that are retained in crustal minerals can provide important insight into the behavior of fluids in the crust. We hypothesized that the 4He/21Ne* may be particularly useful for these purposes because the production of each isotope is fixed at a nearly constant rate of 4He/21Ne*=22x106 in the crust. Nonetheless, following radiogenic/nucleogenic production, the rate of diffusional release of each radiogenic isotope (e.g., 4He*, 21Ne*) from mineral grains in the rock matrix can vary as a function of temperature, mineral phase, and potentially the rate and extent of fluid migration. As a result, measuring the 4He/21Ne* in fluids or rocks provides information on effective rock porosity, temperature, rate, and volume of fluid flow. Here, we examine the 4He and 21Ne* concentrations, and their isotopic ratio, in quartz grains from the Marcellus Shale (Appalachian Basin, USA). Samples include outcrop samples, sub-crop samples collected at differing deformation regimes (e.g., along faults), and from samples collected from the lateral legs of producing wells. Each sample type experienced differing rates and maximum thermal maturities associated with their geological burial histories. Our results reflect fractionation of 4He and 21Ne* according to the thermal maturity of each sample set as well as with respect to the proximity of deformational features.

Determining Carbon Kinetic Isotope Effects Using Headspace Analysis of Evolved CO2.

Isotope ratio mass spectrometry (IRMS) provides accurate measurements of relative abundance of isotopes of heavy atoms for reactions that are subject to kinetic isotope effects (KIEs). The recent development of compound-specific isotope analysis (CSIA) allows the use of multiple time points that provide data for a rate plot as well as isotope ratios. Utilizing CSIA in enzymology presents opportunities for obtaining heavy atom KIEs in diverse areas.

Measurement of uranium-236 in particles by secondary ion mass spectrometry.

The determination of the relative isotopic abundance by secondary ion mass spectrometry of 236U in uranium-containing material is complicated by the presence of 235U1H+ ions at the same nominal mass as the uranium isotopic peak. The net intensity of the 236U signal is usually determined by a peak-stripping procedure, whereby the 235U1H+ contribution is obtained by applying the 238U1H+/238U+ ratio to the 235U+ signal. The subtraction of one signal from another has consequences for the uncertainty of the final 236U abundance determination that may be especially significant when the amount of sample is limited, as is the case with small uranium particles that are of great interest for nuclear safeguards. We have developed a model based on Poisson counting statistics to determine the effects of various parameters on the uncertainty of the 236U abundance, including uranium enrichment level, hydride-to-parent ratio, uranium mass consumed during analysis, single versus multichannel counting, and sample substrate composition. The model predictions have been successfully tested against experimental measurements of uranium oxide particles of both 3% and 90% enrichment in 235U.

Mid-IR enhanced laser ablation molecular isotopic spectrometry

A double-pulsed laser-induced breakdown spectroscopy (DP-LIBS) technique utilizing wavelengths in the mid-infrared (MIR) for the second pulse, referred to as double-pulse LAMIS (DP-LAMIS), was examined for its effect on detection limits compared to single-pulse laser ablation molecular isotopic spectrometry (LAMIS). A MIR carbon dioxide (CO2) laser pulse at 10.6μm was employed to enhance spectral emissions from nanosecond-laser-induced plasma via mid-IR reheating and in turn, improve the determination of the relative abundance of isotopes in a sample. This technique was demonstrated on a collection of 10BO and 11BO molecular spectra created from enriched boric acid (H3BO3) isotopologues in varying concentrations. Effects on the overall ability of both LAMIS and DP-LAMIS to detect the relative abundance of boron isotopes in a starting sample were considered. Least-squares fitting to theoretical models was used to deduce plasma parameters and understand reproducibility of results. Furthermore, some optimization for conditions of the enhanced emission was achieved, along with a comparison of the overall emission intensity, plasma density, and plasma temperature generated by the two techniques.

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.

Recent (2000-2015) developments in the analysis of minor unknown natural products based on characteristic fragment information using LC-MS.

Liquid chromatography-Mass Spectrometry (LC-MS) has been widely used in natural product analysis. Global detection and identification of nontargeted components are desirable in natural product research, for example, in quality control of Chinese herbal medicine. Nontargeted components analysis continues to expand to exciting life science application domains such as metabonomics. With this background, the present review summarizes recent developments in the analysis of minor unknown natural products using LC-MS and mainly focuses on the determination of the molecular formulae, selection of precursor ions, and characteristic fragmentation patterns of the known compounds. This review consists of three parts. Firstly, the methods used to determine unique molecular formula of unknown compounds such as accurate mass measurements, MSn spectra, or relative isotopic abundance information, are introduced. Secondly, the methods improving signal-to-noise ratio of MS/MS spectra by manual-MS/MS or workflow targeting-only signals were elucidated; pure precursor ions can be selected by changing the precursor ion isolated window. Lastly, characteristic fragmentation patterns such as Retro-Diels-Alder (RDA), McLafferty rearrangements, "internal residue loss," and so on, occurring in the molecular ions of natural products are summarized. Classical application of characteristic fragmentation patterns in identifying unknown compounds in extracts and relevant fragmentation mechanisms are presented (RDA reactions occurring readily in the molecular ions of flavanones or isoflavanones, McLafferty-type fragmentation reactions of some natural products such as epipolythiodioxopiperazines; fragmentation by "internal residue loss" possibly involving ion-neutral complex intermediates). © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:202-216, 2018.

Freezing and fractionation: effects of preservation on carbon and nitrogen stable isotope ratios of some limnetic organisms.

Stable isotopes of carbon and nitrogen have become important natural tracers for studying food-web structure and function. Considerable research has demonstrated that chemical preservatives and fixatives shift the isotopic ratios of aquatic organisms. Much less is known about the effects of freezing as a preservation method although this technique is commonly used. We conducted a controlled experiment to test the effects of freezing (-10 °C) and flash freezing (–79 °C) on the carbon and nitrogen isotope ratios of zooplankton (Cladocera), Mysis diluviana and Rainbow Trout (Oncorhynchus mykiss). Subsamples (~0.5 mg) of dried material were analyzed for percentage carbon, percentage nitrogen, and the relative abundance of stable carbon and nitrogen isotopes (δ13C and δ15N values) using a Carlo Erba NC2500 elemental analyzer interfaced to a ThermoFinnigan MAT Delta Plus isotope ratio mass spectrometer. The effects of freezing were taxon-dependent. Freezing had no effect on the isotopic or elemental values of Rainbow Trout muscle. Effects on the δ13C and δ15N values of zooplankton and Mysis were statistically significant but small relative to typical values of trophic fractionation. The treatment-control offsets had larger absolute values for Mysis (δ13C: ≤0.76 ± 0.41‰, δ15N: ≤0.37 ± 0.16‰) than for zooplankton (δ13C: ≤0.12 ± 0.06‰, δ15N: ≤0.30 ± 0.27‰). The effects of freezing were more variable for the δ13C values of Mysis, and more variable for the δ15N values of zooplankton. Generally, both freezing methods reduced the carbon content of zooplankton and Mysis, but freezing had a negative effect on the %N of zooplankton and a positive effect on the %N of Mysis. The species-dependencies and variability of freezing effects on aquatic organisms suggest that more research is needed to understand the mechanisms responsible for freezing-related fractionation before standardized protocols for freezing as a preservation method can be adopted.

Characterization of the designer drug deschloroketamine (2‐methylamino‐2‐phenylcyclohexanone) by gas chromatography/mass spectrometry, liquid chromatography/high‐resolution mass spectrometry, multistage mass spectrometry, and nuclear magnetic resonance

Clinical and forensic toxicology laboratories are challenged every day by the analytical aspects of the new psychoactive substances phenomenon. In this study we describe the analytical characterization of a new ketamine derivative, deschloroketamine (2-methylamino-2-phenylcyclohexanone), contained in seized powders. The analytical techniques employed include gas chromatography/mass spectrometry (GC/MS), liquid chromatography/electrospray ionization coupled with Orbitrap high-resolution/MS (LC/ESI-HRMS), multistage MS (ESI-MS(n)), and NMR. The LC/ESI-HRMS analyses consisted of accurate mass measurements of MH(+) ions in full-scan mode; comparison of experimental and calculated MH(+) isotopic patterns; and examination of the isotopic fine structure (IFS) of the M + 1, M + 2, M + 3 isotopic peaks relative to the monoisotopic M + 0 peak. The collision-induced product ions of the MH(+) ions were studied by both HRMS and MS(n). (1)H and (13)C NMR measurements were carried out to confirm the chemical structure of the analyte. The EI mass spectra obtained by GC/MS analysis showed the presence of molecular ions at m/z 203, and main fragment ions at m/z 175, 174, 160, 147, 146, and 132. The application of LC/ESI-HRMS allowed us to obtain: the accurate mass of deschloroketamine MH(+) ions with a mass accuracy of 1.47 ppm; fully superimposable experimental and calculated MH(+) isotopic patterns, with a relative isotopic abundance value of 3.69 %; and the IFS of the M + 1, M + 2, M + 3 isotopic peaks completely in accordance with theoretical values. Examination of the product ions of MH(+), as well as the study of both (1)H and (13)C NMR spectra, enabled the full characterization of the molecular structure of deschloroketamine. The combination of the employed analytical techniques allowed the characterization of the seized psychoactive substance, in spite of the lack of a reference standard. Deschloroketamine is a ketamine analogue considered to be more potent and longer lasting than ketamine, and this paper is probably the first to report on its analytical characterization.

The cephalopod prey of the Weddell seal, Leptonychotes weddellii, a biological sampler of the Antarctic marine ecosystem

Weddell seals, Leptonychotes weddellii, are important apex predators in the food web of the Antarctic marine ecosystem. However, detailed information on their trophic relationships with cephalopods is scarce. Moreover, cephalopods play a key role in the marine environment, but knowledge of their feeding habits is limited by lack of data. Here, we have combined the use of this seal as a biological sampler together with measurements of the stable isotopic signature of the beaks of their cephalopod prey. Thus, the aims of the present study were: (1) to examine in detail the cephalopod portion of the diet of Weddell seals by means of scat analysis and (2) to assess the habitat use and trophic level of the different cephalopod prey taxa identified. From January to February 2009, a total of 48 faecal droppings were collected at Hope Bay, Antarctic Peninsula. Cephalopods were mainly represented by beaks (n = 83) which were identified to the lowest possible taxonomic level. Furthermore, subsamples of beaks were separated for further isotopic analysis. Relative abundance of stable isotopes of carbon (δ13C) and nitrogen (δ15N) was determined by continuous-flow isotope-ratio mass spectrometry. Cephalopods were represented uniquely by octopods of the subfamily Eledoninae. Pareledone turqueti was the dominant prey species followed by the papillated Pareledone species group and Adelieledone polymorpha. We conclude that Weddell seals preyed primarily on benthic prey resources. Furthermore, the relatively similar δ13C and δ15N values in beaks of the three octopod prey taxa suggest that these share the same type of habitat and occupy similar trophic level positions.

Revised error propagation of 40Ar/39Ar data, including covariances

The main advantage of the 40Ar/39Ar method over conventional K–Ar dating is that it does not depend on any absolute abundance or concentration measurements, but only uses the relative ratios between five isotopes of the same element –argon– which can be measured with great precision on a noble gas mass spectrometer. The relative abundances of the argon isotopes are subject to a constant sum constraint, which imposes a covariant structure on the data: the relative amount of any of the five isotopes can always be obtained from that of the other four. Thus, the 40Ar/39Ar method is a classic example of a ‘compositional data problem’. In addition to the constant sum constraint, covariances are introduced by a host of other processes, including data acquisition, blank correction, detector calibration, mass fractionation, decay correction, interference correction, atmospheric argon correction, interpolation of the irradiation parameter, and age calculation. The myriad of correlated errors arising during the data reduction are best handled by casting the 40Ar/39Ar data reduction protocol in a matrix form. The completely revised workflow presented in this paper is implemented in a new software platform, Ar-Ar_Redux, which takes raw mass spectrometer data as input and generates accurate 40Ar/39Ar ages and their (co-)variances as output. Ar-Ar_Redux accounts for all sources of analytical uncertainty, including those associated with decay constants and the air ratio. Knowing the covariance matrix of the ages removes the need to consider ‘internal’ and ‘external’ uncertainties separately when calculating (weighted) mean ages. Ar-Ar_Redux is built on the same principles as its sibling program in the U–Pb community (U-Pb_Redux), thus improving the intercomparability of the two methods with tangible benefits to the accuracy of the geologic time scale. The program can be downloaded free of charge from http://redux.london-geochron.com.

Isotope Ratio Mass Spectrometry Monitoring of Nitrogen Volatilization from Beef Cattle Feces and 15N-Labeled Synthetic Urine

A 15-day bench-scale manure storage experiment with a slurry mixture comprising beef cattle feces and synthetic urine with 15N-labeled urea was conducted to evaluate the source of volatilized ammonia nitrogen (NH3-N). Beef cattle feces was mixed daily in a 1:2.2 mass ratio with 15N-labeled urine and added for four consecutive days to 2-L storage containers and then left undisturbed for eleven days. Isotope ratio mass spectrometry was used to determine the origin of aerial NH3-N losses from the relative isotopic abundance of N in the 15N-labeled slurry mixture. On average 84% of total NH3-N losses originated from the urine portion and were highest during the first two to four days, when fresh material was added. After fresh material addition ceased, daily NH3-N emission from the urine decreased gradually, whereas emission from the feces remained relatively constant. Calculations showed that over 34% of aerial N was not captured, suggesting that other N gas emission is significant from slurry mixtures. Likely all uncaptured N losses were from urinary urea. The study verified the applicability of 15N-labeled synthetic urine for beef slurry mixtures. However, the results suggest further research to explain and model the NH3 and N release from fecal material is warranted and to determine the identity of the uncaptured N losses.

Accurate Mass Determination of Platycosides Prepared by Macroporous Resins Using High-Resolution Mass Spectroscopy and Optimization Methods

The method using macroporous resin for isolation of platycosides from Platycodi radix extract was developed. The platycosides were detected and analyzed using quadrupole time-of-flight mass spectroscopy in negative ion mode. The employment of chemometric methods effectively reduced the influence of signal intensity or noise on the mass accuracy. Finally, the monoisotopic masses were accurately measured, and relative isotopic abundances of the ions were further investigated. The compound match was obtained by comparison with a specific monomer’s database, and the optimal results allow researchers to narrow their database search window. In addition, the approximate elution order of some isomers was determined via comparison with mass spectrum and chemical structure analysis.

Silicon isotopes: from cosmos to benthos

Silicon is the second most abundant element on the Earth and one of the more abundant elements in our Solar System. Variations in the relative abundance of the stable isotopes of Si (Si isotope fractionation) in different natural reservoirs, both terrestrial (surface and deep Earth) as well as extra-terrestrial (e.g. meteorites, lunar samples), are a powerful tracer of present and past processes involving abiotic as well as biotic systems. The versatility of the Si isotope tracer is reflected in its wide-ranging applications from understanding the origin of early Solar System objects, planetary differentiation, Moon formation, mantle melting and magma differentiation on the Earth, ancient sea-water composition, to modern-day weathering, clay formation and biological fractionation on land as well as in the oceans. The application of Si isotopes as tracers of natural processes started over six decades ago and its usage has seen a sudden increase over the last decade due to improvements in mass spectrometry, particularly the advent of multi-collector inductively coupled plasma mass spectrometers, which has made Si isotope measurements safe and relatively easy while simultaneously improving the accuracy and precision of measurements.

Accurate mass determination of melamine–formaldehyde synthetic polymers after separation on preparative HPLC

Abstract Separation of 57 species from solutions of commercial melamines and analysis by high resolution mass spectrometry using electrospray ionisation and atmospheric pressure chemical ionisation is reported. Structures for melamine-based crosslinked polymers were also confirmed with two orthogonal techniques for characterisation of polymers: Fourier Transform Infrared Spectrometry (FTIR) and Nuclear Magnetic Resonance spectroscopy (NMR), respectively. Accurate mass measurements of melamine–formaldehyde resin structures were achieved in the ppm range, using an internal calibration standard reserpine. Results were within 5 ppm of calculated formulae. Relative isotopic abundances of [M+H] + ions were evaluated for different fractions. Results were independent of the mobile phase used. NMR studies also confirmed structures of fractions and their thermal stability up to 70 °C. Differences in NMR spectra were explained by change of conformation and it was confirmed that this is a reversible process by reheating samples. Stability at 70 °C was confirmed by MS, since when the temperature of the ion transfer capillary in MS was set above this temperature decomposition occurred.

Investigation of the reaction90Zr(p,γ) with in-beamγ-ray spectroscopy

The p nucleus 92 Mo is believed to be mainly produced through photodisintegration reactions in type II supernovae. However, this production scenario cannot solely account for the observed solar relative isotopic abundance of 92 Mo. Additional production scenarios have been suggested to explain this discrepancy. One of these scenarios could be the production of 92 Mo in type Ia supernovae via a chain of proton-capture reactions. To verify this scenario, an accurate knowledge of the involved reaction rates is important. We measured the cross section of 90 Zr(p, γ ) reaction using an enriched 90 Zr target by means of in-beam γ -ray spectroscopy in the energy range between 3.6MeV and 5.1MeV. Since the reactions 90 Zr(p, γ ) and 91 Zr(p,n) produce the same nucleus, the contributions of both reactions have to be disentangled. This procedure is explained in this contribution in detail.

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.

A framework for estimating radiation-related cancer risks in Japan from the 2011 Fukushima nuclear accident.

We present here a methodology for health risk assessment adopted by the World Health Organization that provides a framework for estimating risks from the Fukushima nuclear accident after the March 11, 2011 Japanese major earthquake and tsunami. Substantial attention has been given to the possible health risks associated with human exposure to radiation from damaged reactors at the Fukushima Daiichi nuclear power station. Cumulative doses were estimated and applied for each post-accident year of life, based on a reference level of exposure during the first year after the earthquake. A lifetime cumulative dose of twice the first year dose was estimated for the primary radionuclide contaminants ((134)Cs and (137)Cs) and are based on Chernobyl data, relative abundances of cesium isotopes, and cleanup efforts. Risks for particularly radiosensitive cancer sites (leukemia, thyroid and breast cancer), as well as the combined risk for all solid cancers were considered. The male and female cumulative risks of cancer incidence attributed to radiation doses from the accident, for those exposed at various ages, were estimated in terms of the lifetime attributable risk (LAR). Calculations of LAR were based on recent Japanese population statistics for cancer incidence and current radiation risk models from the Life Span Study of Japanese A-bomb survivors. Cancer risks over an initial period of 15 years after first exposure were also considered. LAR results were also given as a percentage of the lifetime baseline risk (i.e., the cancer risk in the absence of radiation exposure from the accident). The LAR results were based on either a reference first year dose (10 mGy) or a reference lifetime dose (20 mGy) so that risk assessment may be applied for relocated and non-relocated members of the public, as well as for adult male emergency workers. The results show that the major contribution to LAR from the reference lifetime dose comes from the first year dose. For a dose of 10 mGy in the first year and continuing exposure, the lifetime radiation-related cancer risks based on lifetime dose (which are highest for children under 5 years of age at initial exposure), are small, and much smaller than the lifetime baseline cancer risks. For example, after initial exposure at age 1 year, the lifetime excess radiation risk and baseline risk of all solid cancers in females were estimated to be 0.7 · 10(-2) and 29.0 · 10(-2), respectively. The 15 year risks based on the lifetime reference dose are very small. However, for initial exposure in childhood, the 15 year risks based on the lifetime reference dose are up to 33 and 88% as large as the 15 year baseline risks for leukemia and thyroid cancer, respectively. The results may be scaled to particular dose estimates after consideration of caveats. One caveat is related to the lack of epidemiological evidence defining risks at low doses, because the predicted risks come from cancer risk models fitted to a wide dose range (0-4 Gy), which assume that the solid cancer and leukemia lifetime risks for doses less than about 0.5 Gy and 0.2 Gy, respectively, are proportional to organ/tissue doses: this is unlikely to seriously underestimate risks, but may overestimate risks. This WHO-HRA framework may be used to update the risk estimates, when new population health statistics data, dosimetry information and radiation risk models become available.

Accurate Xe isotope measurement using JPL ion trap.

We report an approach for the reproducible and accurate compositional analysis of different mixtures of Xe isotopes using miniature Jet Propulsion Laboratory Quadrupole Ion Trap (JPL-QIT). A major study objective was to validate the recent instrumental improvements to the long-term operational stability under different pressures, temperatures, and trapping conditions. We propose that the present device can be used in certification of trace amounts of isotopes in mixtures dominated by one or more isotopes. Measured isotopic compositions are verified against commercially available standards with accuracy better than 0.07%. To aid the analysis of experimental data, we developed a scalable replica fitting method and use peak areas as descriptors of relative isotopic abundances. This low-power and low-mass device is ideally suited for planetary explorations aimed to enhance quantitative analysis for major isotopes present in small amounts of atmospheric samples.

Matrix effects in laser ablation molecular isotopic spectrometry

Recently, it has been shown that laser-induced breakdown spectroscopy (LIBS) can be used for the detection of isotopes of elements via isotopic shifts in diatomic species in a technique known as laser ablation molecular isotopic spectrometry (LAMIS). While LAMIS works quite well for isotopic analysis of pure compounds under optimal conditions, it is desirable for it to be applicable for a variety of compounds and matrices. However, the LIBS plasma emission associated with LAMIS depends on several parameters, including the applied electric field of the laser pulse, the physical properties of the material being investigated, and the presence of additional elements other than the element of interest. In this paper, we address some of the pitfalls arising from these dependencies when using LAMIS for the determination of the relative isotopic abundance of boron-containing materials with varying chemical matrices.