Search

Rationale: The Δ36S standard deviation measured in a conventional isotope ratio mass spectrometer such as MAT 253 is ca 0.1‰ to 0.3‰. At this precision, it is difficult to resolve the origin of non‐mass‐dependent sulfur isotope fractionation in tropospheric sulfate aerosol and in Martian meteorites or small deviations from the canonical mass‐dependent fractionation laws. Interfering ions with m/z at 131 of 36SF5+ are suggested by the community as the cause of the poor precision, but the exact ion species has not been identified or confirmed. Methods: Here we examined the potential interfering ions by using a Thermo Scientific ultrahigh‐resolution isotope ratio mass spectrometer to measure SF6 working gas and SF6 gases converted from IAEA‐S1/2/3 Ag2S reference materials. Results: We found that there are two resolvable peaks to the right of the 36SF5+ peak when a new filament was installed, which are 186WF42+ followed by 12C3F5+. However, only the 12C3F5+ interference peak was observed after more than three days of filament use. 12C3F5+ is generated inside the instrument during the ionization process. Avoiding the interfering signals, we were able to achieve a Δ36S standard deviation of 0.046‰ (n = 8) for SF6 zero‐enrichment and 0.069‰ (n = 8) for overall measurement start from silver sulfide IAEA‐S1. Conclusions: Aging the filament with SF6 gas can avoid the interference of 186WF42+. Minimizing the presence of carbon‐bearing compounds and avoiding the interfering signals of 12C3F5+ from 36SF5+, we can improve Δ36S measurement accuracy and precision, which helps to open new territories for research using quadruple sulfur isotope composition. [ABSTRACT FROM AUTHOR]

Low temperature superconducting vacuum tube maglev is one of the ultra-high-speed transportation methods that a lot of countries are competing to develop. At present, the research is in its infancy, and it is necessary to evaluate the dynamic performance of its route lines. In this paper, taking the maglev test line from Changsha to Hengyang as an example, a vehicle-route coupling model of the low-temperature superconducting electric levitation system was established, the dynamic performances of the maglev vehicle were determined. Firstly, the vertical and lateral acceleration of the carbody, levitation and guidance force were calculated. Secondly, the frequency histograms of the dynamic performance indicators were drawn, and the distributions of these indicators in different intervals was analyzed. Thirdly, the influence of the different curve radius on the dynamic performance index was obtained. The research shows that when the maglev vehicle travels across the Changsha-Hengyang line, the calculated vertical and lateral accelerations of the carbody are lower than the comfort threshold, and the dynamic performance meets the requirements. From the perspective of vehicle dynamic performance, the transition curve length of 1 400 m is reasonable. When the curve radius is 20 000 m, the vehicle speed 1 000 km/h and the cross slope of 16° match the best dynamic performances. The results in the article can provide references for the design of ultra high speed maglev lines. [ABSTRACT FROM AUTHOR]

Rationale: The Δ 36 S standard deviation measured in a conventional isotope ratio mass spectrometer such as MAT 253 is ca 0.1‰ to 0.3‰. At this precision, it is difficult to resolve the origin of non-mass-dependent sulfur isotope fractionation in tropospheric sulfate aerosol and in Martian meteorites or small deviations from the canonical mass-dependent fractionation laws. Interfering ions with m/z at 131 of 36 SF 5 + are suggested by the community as the cause of the poor precision, but the exact ion species has not been identified or confirmed., Methods: Here we examined the potential interfering ions by using a Thermo Scientific ultrahigh-resolution isotope ratio mass spectrometer to measure SF 6 working gas and SF 6 gases converted from IAEA-S1/2/3 Ag 2 S reference materials., Results: We found that there are two resolvable peaks to the right of the 36 SF 5 + peak when a new filament was installed, which are 186 WF 4 2+ followed by 12 C 3 F 5 + . However, only the 12 C 3 F 5 + interference peak was observed after more than three days of filament use. 12 C 3 F 5 + is generated inside the instrument during the ionization process. Avoiding the interfering signals, we were able to achieve a Δ 36 S standard deviation of 0.046‰ (n = 8) for SF 6 zero-enrichment and 0.069‰ (n = 8) for overall measurement start from silver sulfide IAEA-S1., Conclusions: Aging the filament with SF 6 gas can avoid the interference of 186 WF 4 2+ . Minimizing the presence of carbon-bearing compounds and avoiding the interfering signals of 12 C 3 F 5 + from 36 SF 5 + , we can improve Δ 36 S measurement accuracy and precision, which helps to open new territories for research using quadruple sulfur isotope composition., (© 2024 John Wiley & Sons Ltd.)

The oxygen isotope composition of phosphate is a useful tool for studying biogeochemical phosphorus cycling. However, the current Ag 3 PO 4 method is not only tedious in PO 4 3- extraction and purification but also requires a large-sized sample at the micromole level, thereby limiting its application. Here, we present an approach to measuring the oxygen isotope composition, δ 18 O, of dissolved phosphate at the nanomole level using electrospray ionization Orbitrap mass spectrometry (ESI-Orbitrap-MS). We compared the reproducibility of δ 18 O measurements using the H 2 PO 4 - ions ( m / z = 97 and 99 for H 2 P 16 O 4 - and H 2 P 18 O 16 O 3 - , respectively) and using the PO 3 - fragment ions ( m / z = 79 and 81 for P 16 O 3 - and P 18 O 16 O 2 - , respectively) generated by source fragmentation and by higher-energy collisional dissociation, respectively. The results demonstrate that phosphate δ 18 O can be more reliably measured by the PO 3 - ions than by the H 2 PO 4 - ions. PO 3 - generated by source fragmentation at 40 V achieved the highest reproducibility for δ 18 O based on precision tests. Furthermore, the mass spectrum for a 50:50 μM mixed solution of phosphate and sulfate revealed that PO 3 - ions resulting from source fragmentation at 40 V are the predominant species in the Orbitrap analyzer. Notably, P 16 O 3 - ions ( m / z : 79) are not interfered with by 32 S 16 O 3 - ( m / z : 80) ions. This is in contrast to the case for 1 H 2 P 16 O 4 - ions, which share the same m / z value with 1 H 32 S 16 O 4 - ions and exhibit much lower signal intensity than HSO 4 - ions. Using the PO 3 - fragment method and six phosphate standards with a wide range of δ 18 O values, we obtained a calibration line with a slope of 0.94 ( R 2 = 0.98). The overall uncertainty for ESI-Orbitrap-MS phosphate δ 18 O measurement was 0.8‰ ( n = 30; 1 SD). With much room for improvement, the PO 3 - fragment method presents a better approach to measuring the phosphate oxygen isotope composition, applicable to nanomole sample sizes in a liquid phase.