Intense Ion Research Articles

Characteristic structures of liquid crystal monomers in EI-MS analysis and the potential application in suspect screening

Liquid crystal monomers (LCMs) are of emerging concern due to their ubiquitous presence in indoor and outdoor environments and their potential negative impacts on human health and ecosystems. Suspect screening approaches have been developed to monitor thousands of LCMs that could enter the environment, but an updated suspect list of LCMs is difficult to maintain given the rapid development of material innovations. To facilitate suspect screening for LCMs, in-silico mass fragmentation model and quantitative structure-activity relationship (QSPR) models were applied to predict electron ionization (EI) mass spectra of LCMs. The in-silico model showed limited predictive power for EI mass spectra, while the QSPR models trained with 437 published mass spectra of LCMs achieved an acceptable absolute error of 12 percentage points in predicting the relative intensity of the molecular ion, but failed to predict the mass-to-charge ratio of the base peak. A total of 41 characteristic structures were identified from an updated suspect list of 1606 LCMs. Multi-phenyl groups form the rigid cores of 85% of LCMs and produce 154 characteristic peaks in EI mass spectra. Monitoring the characteristic structures and fragments of LCMs may help identify new LCMs with the same rigid cores as those in the suspect list.

Identification of horn-derived animal medicines based on detection of keratin-derived characteristic peptides

Due to the highly stable structure of keratin, the extraction and dissolution steps of animal medicines rich in keratin are complex, which seriously restricts the detection efficiency and flux. Therefore, this study simplified the pre-treatment steps of horn samples and optimized the detection methods of characteristic peptides to improve the efficiency of identifying the specificity of horn-derived animal medicines. For detection of the characteristic peptides in horn-derived animal medicines treated with/without iodoace-tamide(IAA), the ion pair conditions of the characteristic peptides were optimized, and the retention time, intensity and other data of the specific peptides were compared between the samples treated with/without IAA. Two pre-treatment methods, direct enzymatic hydrolysis and total protein extraction followed by enzymatic hydrolysis, were used to prepare horn-derived animal medicine samples. The effects of different methods on the detection of specific peptides in the samples of Saiga antelope horn, water buffalo horn, goat horn, and yak horn were compared regarding the retention time of specific peptides and ion intensity. The results indicated that after direct enzymatic hydrolysis, the specific peptides in the samples without IAA treatment can be detected. Compared with the characteristic peptides in the samples treated with IAA, their retention time shifted back and the mass spectrometry response slightly decreased. The specific peptides of the samples without IAA treatment had good specificity and did not affect the specificity identification of horn-derived animal medicines. Overall, the process of direct enzymatic hydrolysis can be used to treat horn samples, omitting the steps of protein extraction and dithiothreitol and IAA treatment, significantly improving the pre-treatment efficiency without affecting the specificity identification of horn-derived animal medicines. This study provides ideas for quality research and standard improvement of horn-derived animal medicines.

Research and development activities to increase the performance of the CAPRICE ECRIS at GSI

At GSI the CAPRICE ECRIS is in operation to deliver high charge state ion beams from gaseous and metallic elements to the accelerator facility. A test campaign has been carried out at the ECR test bench to fulfill the demand for higher intensity and stability of high charge state ions and for mixed ion beams. The ion beam stability has been monitored by an Optical Emission Spectrometer (OES), which has been already used to check the plasma and the temperature of the resistively heated oven during metal ion beam operation, particularly for Ca ion beams. During the test campaign, it was investigated that the OES can be used for monitoring the stability of ion beams from gaseous elements and mixed ion beams, and the main achieved results are reported. The ion beams extracted from the ECRIS have been simulated with a particle tracking code in order to study and improve the beam matching into the RFQ. The preliminary results of the study together with possible modifications of the extraction column are presented.

Influence of synchronized pulse bias on the Microstructure and Properties of CrSiN nano-composite ceramic films deposited by MIS-HiPIMS

In this study, CrSiN nano-composite ceramic films with optimized structure were prepared at low temperature using MIS-HiPIMS technique, owing to improved utilization of the high ionization characteristic of HiPIMS under specially designed synchronized pulsed-bias working mode. The correlations of the synchronized pulsed-bias width, the chemical composition, microstructure evolution, mechanical properties and tribological behaviors were studied systematically. According to the results, the waveforms of the pulsed bias experienced obvious fluctuating periods, indicating fluctuating intensities of positive ions arrived at the substrates. Meanwhile, the fluctuating duration increased with increasing synchronized pulse-width, providing an effective way of adjusting the energetic-ion flux for improved bombardment of the growing film. Therefore, obvious microstructure refinement of the as-deposited CrSiN films had been achieved. Due to optimized ion bombardment, the CrSiN films evolved from a coarse and transgranular columnar structure to a more densified columnar structure with the mixture phases of hcp-Cr2N, fcc-CrN as well as a-Si3N4. Moreover, the hardness and elastic modulus of the CrSiN films were also elevated significantly, to the maximum values of 20.2 GPa and 348.3 GPa, respectively. Furthermore, with the best mechanical properties as well as the highest density, the optimized CrSiN film deposited at 400 μs also displayed the most excellent wear resistance, with the wear rate as low as 9.1 × 10−16 m3/N.m. This study not only proposes a method of optimizing the structure and tribological properties of CrSiN nano-composite ceramic films at relatively low temperature, and also enriches the property database of CrSiN films which could expand their application in fields involving thermal-sensitivity materials.

Evolution of ALISES 3 Light Ion Source at CEA Saclay

Since 1995, the Laboratory for Accelerator Studies and Development at CEA Saclay specializes in producing ECR intense Light Ion Sources, for high intensity proton or deuteron. The initial source SILHI (Source d’Ions Légers Haute Intensité) designed for IPHI accelerator in 1995 was the root of sources provided to laboratories worldwide, such as IFMIF, FAIR or SPIRAL2. In parallel, the Ion Source team started a new R&D program on high intensity ECR compact ion sources with the ALISES source family (Advanced Light Ion Source Extraction System). The years spent testing and improving ALISES v1&2 led us to design a new source, named ALISES v3. The development of this source gathers the advantages of each improvement tested on ALISES v1&2, to achieve an even smaller and pragmatic configuration. The manufacturing of ALISES v3 took place during the improvement of the BETSI test bench in 2018, from 50 kV to 100 kV. The goal of this source is to obtain the same characteristics as the original SILHI, with fewer parts and easier maintenance. This article describes the evolution of ALISES v3 and the beam characteristics at every stage. BETSI test bench is equipped with an Allison Scanner and a Faraday cup to analyse the emittance and the beam current.

Study on ion current density of different species in laser produced plasma in a solenoid magnet

A solenoid magnetic field along the expanding laser-produced plasma is an essential technique of the laser ion source. The solenoid field can increase ion beam current at beam extraction point by a factor of 2 to over 100 by confining moving laser produced plasma in transverse direction. This technique is used everywhere from development lab to operational machine for user operation. However, the motion of ions in laser produced plasma is not fully understood. In this study, we experimentally investigated the motion of ions in a solenoid magnet (inner diameter 102 mm, coil length 1980 mm) for Al, Fe, and Ta targets. Using the following three conditions: full solenoid bore, a φ51 mm collimator on the solenoid axis, and a thin-wall φ51 mm tube at the bottom of the solenoid, we found that extracting ions at off-axis position (20∼30 mm from the solenoid axis in this study) can enhance ion intensity by a factor of three or more. We continue to investigate ion motion in a solenoid field to develop better laser ion source design.

Detection of KPC directly from positive blood cultures by MALDI-TOF: From research to the clinical microbiology laboratory routine

Bloodstream infections (BSI) caused by carbapenem-resistant Gram-negative bacilli (CR-GNB) are a subject of major clinical concern, mainly those associated with carbapenemase-producing isolates. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been proposed to detect specific β-lactamases, including KPC. We aimed to detect KPC enzyme directly from positive blood cultures using MALDI-TOF MS. Overall, 146 clinical Gram-negative bacilli (46 CR-GNB) recovered from consecutive blood cultures were evaluated. Proteins were extracted using formic acid, isopropyl alcohol, and water and spotted onto a steel target plate using the double-layer sinapinic acid method. The relative ions intensity ≥120 arbitrary units (a.u.) of a peak close to 28,700 m/z indicated the presence of KPC. The results were compared to HRM-qPCR methodology. This specific peak was observed in 11/14 blood bottles with blaKPC positive isolates (78.6% sensitivity), with 3 false-positive results (97.7% specificity). Analysis from colonies reached identical sensitivity (78.6%), but higher specificity (100%). The detection of KPC peaks directly from positive blood cultures using MALDI-TOF MS is feasible and rapid. It's excellent specificity indicates that positive results are consistently associated with the presence of a KPC producer in positive blood culture.

Preface

Proceedings of the 20th International Conference on Ion Sources, Victoria, BC, Canada, 2023ICIS’23 was the 20th event in a biennial series of conferences that are dedicated to Ion Sources and their applications, and the first in-person conference of this series after the COVID 19 pandemic. The conference was hosted by TRIUMF (www.triumf.ca), Canada’s Particle Accelerator Centre in Victoria, BC, Canada, September 17 to September 22, 2023. The ICIS series covers the physics and technology of ion sources for scientific research and applications. With the conference being the main event within the ion sources community it offers a forum for exchanging of new ideas and establishing of collaborations.The conference was held at the Victoria Conference Centre in Victoria BC, Canada, with support from the adjacent Fairmont Empress hotel. The venue is located on the traditional, ancestral, and unceded territory of the Lkwungen People, also known as the Songhees and Esquimalt First Nations communities.The biennial conference series covers the physics and technology of ion sources for scientific research and applications. New developments and advancements have been presented and discussed. As in previous conferences of this series, all aspects of ion sources have been covered in the categories:• Fundamental processes in ion sources and plasmas• Production of high intensity ion beams• Production of highly charged ion beams• Negative ion sources• Ion sources for fusion• Radioactive ion sources, charge breeders and polarized beams• Beam formation, extraction, transport, and diagnostics• Applications of ion sources• Key technologies for ion sourcesThe conference was organized in a hybrid mode and a zoom link was made available to participants, who could not attend in person. A total of 178 participants have registered for the conference, of whom 20 were students and 23 attended from remote. Fifty contributions have been presented in plenary sessions of which 20 were invited by the international advisory committee. The remaining 30 have been selected by the Scientific advisory committee. 123 contributions have been presented at 2 poster sessions. The high level and interesting contributions triggered lively discussions during all sessions. Thank you to all who contributed to this.Additional events included a tour of the TRIUMF Laboratory on September 17 just before the conference, and a reception on the same evening. In the afternoon of Wednesday, September 20 delegates were able to enjoy the beautiful surrounding Vancouver Island by either participating in a whale watching tour or a nature hike along the shoreline. In the evening of this day the conference banquet was held in the Fairmont Empress hotel.Fifteen students participated in the student poster competition. Members of both the international advisory committee and the scientific program committee acted as judges. Thank you to all the students who have contributed and the judges. Three winners have been awarded.List of International advisory committee, Scientific program committee, Local organizing committee are available in this pdf.

A One‐Dimensional Model of Atmospheric Sputtering at Io Driven by S++ and O+

AbstractIo, the closest of Jupiter's four Galilean moons, suffers from intense ion bombardment from Jupiter's magnetosphere. The constant atmospheric erosion by energetic ion precipitation, referred to atmospheric sputtering, serves as an important mechanism of Io's atmospheric escape. This study is devoted to a state‐of‐the‐art study of atmospheric sputtering at Io, with the aid of constantly accumulated understandings of Io's space environment and atmospheric photochemistry, as well as the updated laboratory measurements. A Monte Carlo model is constructed to track the energy degradation of incident S++ and O+ and atmospheric recoils from which the sputtering yields of different atmospheric species are determined. Our calculations suggest a total escape rate of 3 × 1029 atom s−1 on Io, and SO2 is the dominant sputtered species. Further investigations reveal that S++ is the most efficient species for atmospheric sputtering on Io, and sputtering yields increase substantially with increasing incident ion mass, energy, and incidence angle. The model sensitivity to different influence factors is also discussed, including scattering angle distribution, atmospheric column density, proton precipitation, inelastic process, and surface sputtering, of which the former two dominate.

Application of Optical Emission Spectroscopy to Electron Cyclotron Resonance Ion Sources

Electron Cyclotron Resonance Ion Sources (ECRIS) are widely used for production of highly charged high intensity ion beams for research, medical and industrial applications.ECRIS performances, especially the charge state distribution and beam intensity, depend significantly on the electron energy distribution function that ranges from a few eV to hundreds of keV. Further improvements of ECRIS performances require a deeper and deeper understanding of the plasma heating mechanisms and ion generation by means of opportune plasma diagnostics. Amongst others, optical emission spectroscopy (OES) is the most remarkable for application in ECRIS: it is a non-invasive diagnostics able to operate also in high-voltage conditions and it requires small room for operation. OES has been already tested for plasma diagnostics in proton sources.This work presents the experimental set-up developed for the plasma diagnostics of the Advanced Ion Source for Hadrontherapy (AISHa), an ECRIS for medical applications, together with the strategy applied to relate plasma emission lines in the visible and near-infrared domain to plasma parameters for some ions of interest. Preliminary results and perspectives will be also discussed.

Influence of the Capillary Design and Conditions upon the Transmission Efficiency of a Portable Ion Trap Mass Spectrometer

The capillary is a widely used atmospheric pressure interface in mass spectrometers that may be heated to enhance the desolvation of ions. In this study, the ion transmission efficiency of a portable ion trap mass spectrometer was investigated using capillaries with different inner diameters and temperatures, different vacuum pressures, and different ion optics designs. Due to the incomplete desolvation and the space charge effect inside the miniature ion funnel, the increase of ion intensities with the inner diameter of the capillary leveled off when the inner diameter of the capillary was larger than 0.37 mm. With the increase of capillary temperature, the ion intensities first increase due to better desolvation and then decrease due to greater diffusion loss. The optimal temperature of the capillary increases with the inner diameter of the capillary and the mass-to-charge ratio of ion. In addition, the pressures of different vacuum stages also exerted remarkable effects on the sensitivity of the portable mass spectrometer. From the perspective of instrument miniaturization, optimal transmission efficiency can be obtained when the first-stage vacuum pressure is maintained from 4 to 6 mbar. For a capillary with an inner diameter of 0.37 mm, the background of mass spectrum can be significantly reduced by replacing the pinhole behind the ion funnel with an off-axis skimmer.

Mass Spectrometry-Imaging Analysis of Active Ingredients in the Leaves of Taxus cuspidata.

Taxus cuspidata is an endangered evergreen conifer mainly found in Northeast Asia. In addition to the well-known taxanes, several active ingredients were detected in the leaves of T. cuspidata. However, the precise spatial distribution of active ingredients in the leaves of T. cuspidata is largely unknown. in the present study, timsTOF flex MALDI-2 analysis was used to uncover the accumulation pattern of active ingredients in T. cuspidata leaves. In total, 3084 ion features were obtained, of which 944 were annotated according to the mass spectrometry database. The principal component analysis separated all of the detected metabolites into four typical leaf tissues: mesophyll cells, upper epidermis, lower epidermis, and vascular bundle cells. Imaging analysis identified several leaf tissues that specifically accumulated active ingredients, providing theoretical support for studying the regulation mechanism of compound biosynthesis. Furthermore, the relative accumulation levels of each identified compound were analyzed. Two flavonoid compounds, ligustroflavone and Morin, were identified with high content through quantitative analysis of the ion intensity. our data provides fundamental information for the protective utilization of T. cuspidata.

Stability of titanium deuteride films irradiated with pulsed ion beams

Titanium deuteride films are widely used as target materials for neutron generators. Intense pulsed ion beams irradiated titanium deuteride films, and their structure stabilities were investigated by combination with scanning electron microscopy, transmission electron microscopy, grazing incidence angle X-ray diffraction, slow positron beam, scratch test and finite element analysis. The beam energy density was 0.3 J/cm2. Five different irradiation fluences of 3 × 1014, 1 × 1015, 3 × 1015, 1 × 1016, 3 × 1016 cm−2 were performed at room temperature. The adhesion strength between the film and Mo substrate decreased with increasing fluence. Moreover, surface melting and grain growth occurred after the beam irradiation with fluences over 3 × 1015 cm−2. The morphology of scratch tracks shows that the titanium deuteride film suffers a transition from ductile fracture to brittle fracture with increasing fluence. The reason for the decreasing adhesion strength was discussed via the introduction of thermal stress and lattice structure recovery. The research result is critical for evaluating the lifetime of titanium deuteride films based on failures in structures and a decrease in concentration of the inner deuterium.

A blood test to monitor bee health across a European network of agricultural sites of different land-use by MALDI BeeTyping mass spectrometry

There are substantial concerns about impaired honey bee health and colony losses due to several poorly understood factors. We used MALDI profiling (MALDI BeeTyping®) analysis to investigate how some environmental and management factors under field conditions across Europe affected the honey bee haemolymph peptidome (all peptides in the circulatory fluid), as a profile of molecular markers representing the immune status of Apis mellifera. Honey bees were exposed to a range of environmental stressors in 128 agricultural sites across eight European countries in four biogeographic zones, with each country contributing eight sites each for two different cropping systems: oilseed rape (OSR) and apple (APP). The full haemolymph peptide profiles, including the presence and levels of three key immunity markers, namely the antimicrobial peptides (AMPs) Apidaecin, Abaecin and Defensin-1, allowed the honey bee responses to environmental variables to be discriminated by country, crop type and site. When considering just the AMPs, it was not possible to distinguish between countries by the prevalence of each AMP in the samples. However, it was possible to discriminate between countries on the amounts of the AMPs, with the Swedish samples in particular expressing high amounts of all AMPs. A machine learning model was developed to discriminate the haemolymphs of bees from APP and OSR sites. The model was 90.6 % accurate in identifying the crop type from the samples used to build the model. Overall, MALDI BeeTyping® of bee haemolymph represents a promising and cost-effective “blood test” for simultaneously monitoring dozens of peptide markers affected by environmental stressors at the landscape scale, thus providing policymakers with new diagnostic and regulatory tools for monitoring bee health.

Modeling Ion Conic Formation in Io's Auroral Footprint

AbstractEnergetic ions outflowing from Jupiter's atmosphere was observed during Juno's 12th perijove crossing (PJ12) in the vicinity of Io's auroral footprint and reported by prior studies. It was hypothesized that Wave‐Particle Interactions (WPI) with ion cyclotron waves observed coincident with the ion outflow may be responsible for the heating and subsequent outflow. This study uses numerical simulation and data model comparison to test whether ion cyclotron resonant heating is indeed a plausible mechanism to explain the intense ion outflow observed. Our simulations assume that the wave heating is of limited duration due to Io's footprint motion. The simulations are moreover compared to the previously published Jupiter Energetic Particle Detector Instruments (JEDI) observations at high energies, and the lower energy Jovian Auroral Distributions Experiment (JADE) observations that were not previously reported. We find that the ion cyclotron resonant heating mechanism can indeed lead to ion conic formation and strong vertical transport under certain assumptions about the distribution of wave power with altitude. We also find that the ion outflow is energized quickly with very rapid formation of the ion conic distribution. The implications of the intense ion outflow are also examined and it is found that such strong wave heating can lead to a depletion of the topside ionosphere.

Numerical study of the plasma meniscus shape and beam optics in RF negative ion sources

In order to extract intense ion beams with good beam optics from hydrogen negative ion sources, it is important to control the shape of the plasma meniscus (i.e. beam emission surface). Recently, it is suggested experimentally that the degradation of beam optics in the RF negative ion sources may be due to the fluctuation of the distance d eff between the meniscus and the extraction grid caused by the fluctuation of the plasma density np . The purpose of this study is to make clear the dependence of d eff on np in the presence of a large amount of surface produced H- ions in order to understand such fluctuation of beam optics in RF sources For the purpose, 3D electrostatic PIC simulation was conducted taking the bulk plasma density as a parameter, investigating the extraction region of a H- ion source. A large amount of the surface H- production on the PG has been taken into account under the assumption that the H- production rate is proportional to the bulk plasma density. The result shows that the effective distance d eff is proportional to np -1/2 even for a large amount of surface H- production. This dependence suggests that the bulk plasma density np is the key parameters to control d eff and the resultant beam optics extracted from the negative ion source.

Development of a Modular, Open-Source, Reduced-Pressure, Drift Tube Ion Mobility Spectrometer.

Toward the goal of minimizing construction costs while maintaining high performance, a new, reduced-pressure, drift tube ion mobility system is coupled with an ion trap mass analyzer through a custom ion shuttle. The availability of reduced-pressure ion mobility systems remains limited due to comparatively expensive commercial options and limited shared design features in the open literature. This report details the complete design and benchmarking characteristics of a reduced-pressure ion mobility system. The system is constructed from FR4 PCB electrodes and encased in a PTFE vacuum enclosure with custom torque-tightened couplers to utilize standard KF40 bulkheads. The PTFE enclosure directly minimizes the overall system expenses, and the implementation of threaded brass inserts allows for facile attachments to the vacuum enclosure without damaging the thermoplastic housing. Front and rear ion funnels maximize ion transmission and help mitigate the effects of radial ion diffusion. A custom planar ion shuttle transports ions from the exit of the rear ion funnel into the ion optics of an ion trap mass analyzer. The planar ion shuttle can couple the IM system to any contemporary Thermo Scientific ion trap mass analyzer. Signal stability and ion intensity remain unchanging following the implementation of the planar ion shuttle when compared to the original stacked ring ion guide. The constructed IM system showed resolving powers up to 85 for various small molecules and proteins using the Fourier transform from a ∼1 m drift tube. Recorded mobilities derived from first principles agree with published literature results with an average error of 1.1% and an average error toward literature values using single field calibration of <1.3%.

Study on effect of magnetization on wetting characteristics of water with different ions to coal dust

Coal dust is a significant problem in underground coal mining, and more economical and effective methods are needed to control coal dust. Magnetized water dust removal technology is considered to be an effective method to solve the problem of high concentration dust. In order to further understand the role of ions in magnetic fields in water, the optimal magnetic field parameters for solutions containing various ions were determined by surface tension and contact angle measurements. The wettability experiments have shown that the optimal magnetization effect can be obtained by placing NaCl solution with the concentration of 0.04 mol/L in the 150mT magnetic field for 120 s at room temperature. Subsequently, the influence of various ions in water on the wettability of coal was investigated using a combination of FTIR testing and Zeta potential experiments. The results showed that the order of the influence intensity of different ions on the wettability of water was Na+ > Mg2+ > Ca2+ when the Cl– content was 0.04 mol/l, and Cl– > CO32– > SO42– when the Na+ content was 0.04 mol/L. Furthermore, Lorentz forces can influence various ions, accelerating their migration and enhancing their accessibility to water clusters. Different ions exert force on the dipoles within water molecules, which can promote or suppress hydrogen bond cleavage. When the number of hydrogen bond breaks rises, it leads to an increase in the wetting properties of the solution. The research findings provide a theoretical foundation for the use of magnetization technology in dust suppression with mist spray in underground coal mines.

Isomeric differentiation of bile acids using three‐dimensional MS2 spectrum

AbstractBile acids (BAs) currently occupy the research hotspot because of their unreplaceable physiological functions as well as their unique abilities to reflect the physiopathological status. It is always challenging to characterize BAs‐submetabolome using LC–MS/MS, primarily attributing to the high‐level structural diversity. The key obstructing confirmative identification is isomeric identification because of the inherent “isomer‐blind” disadvantage of MS/MS. The isomerism styles of BAs are broadly divided into: type‐I, 5α‐H and 5β‐H epimers; type‐II, α‐OH and β‐OH epimers; type‐III, C‐OH positional isomers; and type‐IV, hybrid isomers bearing two or more isomerism fashions. Herein, we aim to comprehensively pursue isomer‐selective clues for BAs through constructing three‐dimensional MS2 (3D‐MS2) spectrum that was accomplished by fortifying energy‐resolved MS (ER‐MS) program as the new dimension. The breakdown graphs of primary MS2 spectral signals composed of 3D‐MS2 spectrum namely full collision energy ramp (FCER)‐MS2 spectrum for each BA species after appropriate normalization, and seven isomeric BAs covering all isomerism styles were utilized as representative cases. After recording MS2 spectra with progressive CE levels, differences were observed for their FCER‐MS2 spectra. Diagnostic fragment ions (DFIs) occurred within type‐I, type‐II, type‐III or type‐IV isomers, and noteworthily, 2.02 Da neutral loss discriminated BAs containing cis‐6,7‐diol and trans‐6,7‐diol functional groups. Notably, the features such as the maximal relative ion intensity (RIImax) and optimal CE (OCE) enabled isomeric differentiation for all types, even type‐II and type‐III isomers. Above all, it is feasible to acquire in‐depth isomer‐selective MS/MS clues for BAs using FCER‐MS2 spectrum, regardless of the isomerism manner.

Phosphorothioate RNA Analysis by NETD Tandem Mass Spectrometry

Therapeutic RNAs are routinely modified during their synthesis to ensure proper drug uptake, stability, and efficacy. Phosphorothioate (PS) RNA, molecules in which one or more backbone phosphates are modified with a sulfur atom in place of standard nonbridging oxygen, is one of the most common modifications because of ease of synthesis and pharmacokinetic benefits. Quality assessment of RNA synthesis, including modification incorporation, is essential for drug selectivity and performance, and the synthetic nature of the PS linkage incorporation often reveals impurities. Here, we present a comprehensive analysis of PS RNA via tandem mass spectrometry (MS). We show that activated ion-negative electron transfer dissociation MS/MS is especially useful in diagnosing PS incorporation, producing diagnostic a- and z-type ions at PS linkage sites, beyond the standard d- and w-type ions. Analysis using resonant and beam-type collision-based activation reveals that, overall, more intense sequence ions and base-loss ions result when a PS modification is present. Furthermore, we report increased detection of b- and x-type product ions at sites of PS incorporation, in addition to the standard c- and y-type ions. This work reveals that the gas-phase chemical stability afforded by sulfur alters RNA dissociation and necessitates inclusion of additional product ions for MS/MS of PS RNA.