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Natural processes, from cosmochemistry to human homeostasis, can be traced by means of the mass-dependent fractionation of K isotopes because the 39K/41K ratio is characterized by a wide range of variations (ca. 3‰). The measurement of the 39K/41K ratio is traditionally achieved by multi-collector inductively coupled plasma mass spectrometers (MC-ICPMS), but is significantly impeded by large isobaric argide interferences on K isotopes. A new generation of MC-ICPMS equipped with a collision/reaction cell allows the quantitative elimination of argide interferences using H2 as a reaction gas. We report on a set of high-precision K isotopic data obtained with the recently released ThermoScientific Neoma MC-ICPMS/MS equipped with a prefiltering system consisting of a double-Wien filter and a collision/reaction cell. In the low-resolution mode, the mass resolving power is ca. 2200, resulting in a K sensitivity of ca. 1000 V ppm-1 for 39K in dry mode with an Apex Omega desolvator. This large mass revolving power allows the observation of yet undetected interferences on the high-mass shoulders of 39K and 41K. The interference is ca. 25 mV on 39K and 1 mV on 41K in the low-resolution mode, similar in K and blank HNO3 (0.05 M) solutions, increases when N2 is added in the desolvator and decreases when He is added as a collision gas. The presence of these interferences, which contribute modestly < 0.02% of the K signal, is probably the result of the formation of complex organic compounds in the collision/reaction cell. However, blank subtraction is a critical step to achieve steady and accurate analysis of the 39K/41K ratio. The overall stability of the analysis of the 39K/41K ratio is greatly improved by using a continuous-flow microFAST Isotope autosampler. A survey on the potential effects of sample-standard mismatches reveals significant offsets for matrix elements (Ca, Mg and Na), no offset for acid molarity. Regarding the effect of sample-standard concentration mismatch, we show that the amplitude of the offset is session-dependent, such that no general correction could be applied. We use the autosampler adjustable injection flow rate to correct for a concentration mismatch up to ± 30% to recover expected K isotope composition within the ± 0.05‰ uncertainty. In these conditions, short-term external precision and long-term reproducibility are 0.07‰ (2SD, n = 500) and 0.08‰ (2SD, n = 66), respectively. For validation of the overall method, we finally purified K using a single step chemical separation by ion exchange chromatography, and measured the K isotope composition of geological and biological reference materials, for which we found values similar to the literature. Our study shows that the Neoma MC-ICPMS/MS with continuous flow injection is a robust instrumentation that will contribute to expediting high-precision K isotopic measurements for various applications. [ABSTRACT FROM AUTHOR]

A prefiltering system made up of a double-Wien filter and a collision/reaction cell is included with the new Neoma MC-ICPMS/MS to reduce spectral interferences and allow high-precision isotope analyses. In the present study, we challenge these capabilities for measuring Sr isotopes. We first test the effect of different combinations of magnetic and electrostatic field values in the double-Wien filter on the transmission of a bandpass window that includes Sr isotopes and their reaction products. We next scrutinize the spectrum of ion products resulting from the introduction of N2O or SF6 to remove on-line Rb which interferes with Sr on the 87-mass unit. While N2O is the preferred reaction gas when using ICPMS/MS, we found that it reacts with Sr to create expected Sr16O products, but also 14N- and, most probably, 18O-based interfering products. By contrast, the introduction of SF6 generates a more resolved spectrum of F-based products, notably because F is mono-isotopic, but leads to a 50% reduction in signal intensity. Care must, however, be taken to measure 88SrF+ in a mass range free of the 32S19F316O+ interference. We then measure the 87SrF/86SrF ratio first in raw solutions of a suite of geological reference materials without prior Sr extraction and second in sintered in-house materials and natural solid samples using laser ablation. In the solution mode, no RbF+ is detectable and the sensitivity is ∼50 V ppm−1 for 88SrF+. The accurate measurements of the 87SrF/86SrF ratio of the geological reference materials are achieved with an uncertainty of 70 ppm (±2 SD), which is comparable with that typically obtained using MC-ICPMS with prior Sr extraction. In the laser ablation mode, the performance without SF6 of the Neoma for measuring Sr isotopes in homogeneous materials is roughly equivalent to that of the Neptune MC-ICPMS. With SF6, the Neoma MS/MS exhibits a sensitivity of ∼8 mV ppm−1 (based on 88SrF) and the measurement of the 87SrF/86SrF ratio has a short-term external precision of ∼0.0015 (±2 SD). Finally, an analysis of a heterogeneous material (a fossil tooth) reveals more well-resolved spatial variations of the 87SrF/86SrF ratio than of the 87Sr/86Sr ratio, likely thanks to the absence of 87RbF+. [ABSTRACT FROM AUTHOR]

Rationale: Understanding the interactions between marine mammals and their environment is critical for ecological and conservation purposes. Odontocetes offer a continuous record of their life history from birth as recorded in annual increments of their tooth dentine. Because dentine is not remodeled and contains collagen, nitrogen stable isotope compositions (δ15N) reflect nursing and weaning events, life history traits that would otherwise be impossible to retrieve in such elusive marine animals. Yet, capturing the magnitude and temporal changes in these events is constrained by tooth size and sampling resolution. Moreover, historical and fossil specimens undergo collagen decay, hence the need to develop the measurements of other proxies. Methods: Here, we present a multiproxy approach to investigate the use of Ca isotope compositions (δ44/42Ca) in relation to δ15N and laser ablation profiles for different trace metal (Ba, Mg, Sr, Zn) concentrations across the dentine of a single individual of the common bottlenose dolphin Tursiops truncatus. Results: To help interpret the dentine data, we provide milk elemental compositions and δ44/42Ca values for two odontocete individuals. We discuss the observed changes in δ44/42Ca across the dentine as potential markers of birth, weaning interval, incidental ingestion of seawater, trophic level and physiology. Incidental ingestion of seawater during nursing induces a positive offset in δ44/42Ca values recorded in the early formed dentine. Conclusions: Life history parameters of individual marine mammals are extremely difficult to retrieve due to limitations in observing specimens in the wild and the methodology presented here offers new ecological and paleoecological perspectives. [ABSTRACT FROM AUTHOR]

The new Neoma MC-ICPMS/MS is equipped with a prefiltering system consisting of a double-Wien filter and a collision/reaction cell whose performances are challenged using different combinations of magnetic and electrostatic field values and adjustable slit apertures. The results show an asymmetrical attenuation of transmission relative to the chosen axial mass-to-charge value, with higher efficiency at removing low masses than high masses, even when magnetic induction is minimal. The resulting asymmetry of the bandpass window is fully predictable by theoretical calculations of ion trajectories in a Wien filter, either as a function of the magnetic field value or that of the aperture of the adjustable slit. With an axial mass-to-charge value set at 120Sn, the vertical deviation for a magnetic field value at 100% will be approximately 3 mm and 4 mm for a variation of mass-to-charge of ±20%, respectively. In these conditions, Ar was already barely detectable with the lowest magnetic field value (10%) and a fully open adjustable slit, while Pb is quantitatively transmitted. We then use the prefiltering system to remove on-line the 40Ar23Na+ compound that produces an isobaric interference with 63Cu, hampering high-precision measurement of Cu stable isotope composition (65Cu/63Cu). While Na is not transmitted thanks to the double-Wien filter, 40Ar23Na+ still interferes with 63Cu, demonstrating that this argide is produced in the plasma source but not in the reaction cell. Helium in the collision/reaction cell is necessary to remove the 40Ar23Na+ interference. The MS/MS technology of the Neoma allows for the correction of the 40Ar23Na+ interference up to a Na/Cu ratio of 10, where other classic MC-ICPMS already show an offset of the Cu stable isotope composition for a Na/Cu ratio of 1. The inability to correct the Cu stable isotope composition with a Na/Cu ratio higher than 10 suggests that the Na-based interference is no longer spectral and becomes linked to the matrix. We next measure the Cu stable isotope composition in eight certified reference materials prepared with a simple automated single step ion-chromatography procedure to purify Cu. The results show a very good agreement with previously reported values. The overall results suggest that the MS/MS technology of the Neoma MC-ICPMS allows efficient on-line isolation of analytes, therefore reducing potential spectral and matrix interferences to permit much better resolved and controlled subsequent effects in the collision/reaction cell. [ABSTRACT FROM AUTHOR]