We report the mass spectra and anion photoelectron spectra of both uranium and thorium cluster anions generated using a laser-vaporization source (LVS). Our mass spectra demonstrate the LVS source’s propensity to generate primarily uranium oxide cluster anions. An examination of the anion photoelectron spectra (aPES) for both systems shows that the thorium species exhibit more spectral structure than do the uranium species. This is an electronic structure difference that may reflect the absence of 5f electrons in thorium versus their presence in uranium. We also report the vertical detachment energies (VDEs) for each measured system, with an uncertainty of ±50 meV. These experimental benchmarks may be valuable for future challenging theoretical work on these species.
We report an experimental investigation into the influence of plasma conditions on uranium (U) isotope ratios measured by multi collector (MC) – inductively coupled plasma (ICP) – mass spectrometry (MS). We examine a total of five plasma conditions: three wet plasma states at different temperatures and one dry plasma state on the Neoma MC-ICP-MS, in addition to one wet plasma state on a NeptunePlus MC-ICP-MS. U isotope standards in their pure form (e.g. only diluted with 2% HNO3), as well as doped with progressively increasing quantities of the nuclear fuel cycle relevant elements lead (Pb) and platinum (Pt), were examined across all of the plasma conditions and instruments. Data from the IRMM-2025 U isotope standard analyzed in its pure form indicate that hotter plasma conditions partially mitigate, but do not eliminate, space-charge induced instrumental mass fractionation. Data from Pt and Pb doping experiments of the IRMM-2020 standard yield similar results regarding the minimal influence of plasma temperature. However, the perturbations induced by the dopants themselves are major, with Pt and Pb showing fundamentally different effects. The Pt doping experiments perform as expected in that the polyatomic Pt-based interferences result in isotope-specific augmentation of the U signal whereas the addition of Pb results in substantial attenuation of the 234U and 236U signal. This behavior cannot be explained solely on the basis of the ‘space-charge’ effect, but rather suggests that the introduction of Pb may result in a reduction of the plasma's ability to effectively ionize U within the interface regions of the Neoma and Neptune MC-ICP-MS instruments.
Nanospray desorption electrospray ionization mass spectrometry (nano-DESI MS) uses specially designed probes to achieve a stable liquid bridge on the sample surface, ensuring consistent analyte extraction. Here, we present a mold-based fabrication protocol for cyclic olefin copolymer (COC) microfluidic probes (MFPs). We describe mold design, probe fabrication, and probe setup for nano-DESI MS. Four mold fabrication methods, including computer numerical control (CNC) machining, metal 3D printing, photolithography, and selective laser-assisted etching (SLE), were evaluated, with SLE providing the highest structural precision and enabling reproducible channel fabrication. Performance evaluation using lysophosphatidylethanolamine (LPE) 17:1 standard demonstrated stable liquid bridge formation, clear spatial separation, reproducible signal response, and low background interference. This mold-based fabrication strategy produces reproducible, low-cost probes and offers an accessible approach for nano-DESI MS.
This manuscript presents a unified treatment of cylindrical electrode architectures for quadrupole and higher-order multipole operation, formulated throughout in the real Clifford algebra Cl(1,3). The central practical question is whether cylindrical arrangement of electrodes can serve as a credible alternative to the conventional precision rod assembly. Two closely related geometries are studied. The first is the axial strip-electrode cylinder, intended primarily for transverse quadrupole mass filtering but also reconfigurable into higher-order multipole modes for accumulation, cooling, and transport. The second is the generalized axisymmetric segmented three-dimensional trap, constructed from cylindrical wall bands and concentric endcap rings, and analyzed as the three-dimensional analogue of the same boundary-synthesis philosophy.Conventional rod quadrupoles are themselves approximate realizations of the ideal hyperbolic field. The question is whether the electrode geometry produces a field that is sufficiently quadrupolar in the dynamically useful region that the intended ion-optical function is preserved. In the two-dimensional strip geometry, the quadrupole field is synthesized explicitly as the n=2 boundary harmonic, and the first parasitic aliases are pushed to high order when the number of strips is large. In the three-dimensional axisymmetric geometry, the same logic appears as the cancellation of the lowest even solid harmonics H4,H6,… by suitable choice of segment weights. In both cases, additional segmentation improves harmonic purity, but only subject to the practical constraints imposed by electrical loading, inter-electrode capacitance, gap-edge fields, conditioning of the harmonic coefficient matrix, and manufacturability.The resulting conclusion is that neither the strip-electrode quadrupole nor the segmented three-dimensional trap is claimed a priori to outperform conventional rod or hyperbolic geometries. However, both are sufficiently well-founded theoretically, and sufficiently attractive from the standpoint of manufacture and reproducibility, to justify full numerical and engineering evaluation.
The production of biofuels such as ethanol has increased not only due to environmental concerns, but also because blending ethanol with gasoline improves fuel physicochemical properties. However, excessive ethanol content in ethanol-gasoline mixtures may compromise fuel quality, raising concerns for both consumers and regulatory agencies. This scenario highlights the need for analytical methodologies capable of quantifying ethanol in gasoline with high speed, selectivity, sensitivity, and cost-effectiveness. High-throughput mass spectrometry (HTMS), widely used in drug discovery and bioassays, has recently gained attention in other industrial applications, including fuel quality control. In this work, an HTMS method based on Venturi easy ambient sonic-spray ionization (V-EASI) was developed for the quantification of ethanol in gasoline, employing nicotinoyl chloride as an online derivatization reagent. The proposed approach enables rapid analysis, achieving a throughput of one sample per minute, while maintaining analytical performance in accordance with ICH Q2 validation guidelines.
Ion mobility spectrometry-mass spectrometry (IMS-MS) has emerged as a mainstream analytical technique for rapidly separating challenging molecular species as well as being complementary to existing omics-based workflows. With new technological advancements and commercial instrumentation, the ability to perform high-resolution measurements has become more available to users. This has opened the door for tackling previously intractable isomeric species as well as newer avenues of research focusing on fundamental ion structure. In this young investigator perspective, I will highlight the area of research known as isotopic shifts, or rather the separations of isotopologues and isotopomers with IMS-MS, and its applications and fundamental studies.
In addition to the interest in actinides because of their use in nuclear fuel cycles and remediation, the ThF+ molecule has been proposed as an ideal system to measure the nuclear Schiff moment. Here, we investigate the formation and reactivity of the ThF+ molecule associated with the fluorine donor, CF4. The kinetic energy dependences of the reactions of atomic thorium and uranium, thorium monofluoride, and thorium difluoride cations with CF4 were studied using guided ion beam tandem mass spectrometry. The products observed include AnFx+ (An = Th or U, x = 1-3). According to literature thermochemistry, these reactions should all be exothermic, but all cross sections display strong endothermic features with thresholds just below or near 2 eV. In contrast to a previous study that reported inefficient formation of AnF+ + CF3 at low energies for both actinides, we find this reactivity was associated with a AnO+ contaminant, and none of the AnF+ + CF3 product channel is actually formed at thermal energies. Overall, these results indicate that the reactions of Th+ and U+ and the thorium fluoride cations with CF4 are not thermodynamically driven.
A kinematically complete characterization of the fragmentation dynamics of the deuterium molecule induced by 20 keV He2+ ion impact was conducted through both theoretical and experimental approaches. The observed dynamics are predominantly governed by the Coulomb Explosion (CE) model. Angular distributions of the resulting fragments exhibit a pronounced back-to-back emission pattern, consistent with the axial recoil approximation. Multiple ionization and fragmentation channels were identified. This study focuses exclusively on the fragmentation of the doubly ionized D2 molecule (D2 (X1 Sigma g+) + He2+-* D22+-* D+ + D+). A distinct peak centered at 9.75 eV is observed in the kinetic energy release (KER) spectrum corresponding to this process. The experimentally measured KER distribution shows good agreement with Classical Trajectory Monte Carlo (CTMC) calculations. The influence of molecular orientation on the KER spectrum was examined, revealing that the KER of both fragments is higher when the molecular axis is aligned parallel to the incident beam compared to a perpendicular orientation. The KER distribution also demonstrates a clear correlation with the impact parameter: as the impact parameter decreases, the KER increases significantly. The momentum vectors of both D+ fragments in the scattering plane reveal a ring-like structure characteristic of the Coulomb explosion process. Furthermore, the impact parameter dependence of the D+ fragment momenta was investigated, showing a strong correlation.
Studying the dissociation of triphenylmethanes, provides critical insights into their structural and bonding characteristics. Here, the dissociation mechanism of cationic and anionic forms of Bromophenol blue (BPB) [C19H10Br4O5S] was examined by subjecting it to in-source and collision-induced dissociation (CID) using an electrospray ionization quadrupole time-of-flight mass spectrometer and compared with the fragments simulated by QCxMS simulation software employing the semiempirical tight-binding method GFN2-xTB. BPB cations dissociate via two parallel pathways, involving C-C and C-S, C-Br bond cleavages, generating primary product ions [C13H7Br2O4S]& sdot;& sdot;+ and [C19H9Br3O2]& sdot;+. Simulations may suggest a fluorene-like structure. The subsequent dissociation was identified as the sequential dissociation of Br radicals. BPB anions exhibit competing C-C and C-Br cleavages, forming major product ions [C6H3Br2O]- and [C19H9Br3O5S]& sdot;-.Breakdown curve experiments of BPB reveal distinct fragmentation kinetics and the experimental results are substantiated by molecular dynamics simulations, showing a significant correlation between the experiment and simulation. Altogether this study shows that the internal energy of protonated BPB is perhaps greater than the internal energy of deprotonated BPB. Photo dissociation of BPB in condensed phase under UV irradiation (lambda max = 254 nm) further confirmed Br and SO3 cleavages, complementing the CID observations. The proposed mechanisms and this integrated experimental-simulation approach may aid in analyzing the spectra of similar triaryl methane analogs.
During the last two decades, a change in the consumption of illicit drugs became evident. So called New Psychoactive Substances (NPS) entered the drug market in addition to known drugs, such as cocaine and amphetamine. Intention was to circumvent law and to generate new compounds with similar chemical structures to mimic classic drugs. Since there is neither quality control nor clinical investigation, these completely new compounds represent a hazard. By the end of 2023 the European Union Drugs Agency (EUDA) monitored more than 1000 different NPS. To get more insight about these compounds, an EU project namely NextGenPS was launched with the goal to choose and investigate eight different substances out of three different compound classes: Two phenylethylamines (25B-NBF and 25I-NBF), three tryptamines (5-MeO-MALT, 5-MeO-pyrT and 5-Cl-DMT) and three cathinones (4F-3Me-alpha-PVP, alpha-D2PV and 3F-NBF). These NPS were chosen, since they are expected to enter the global drug market. After synthesis of these compounds by a partner group, characterisation was conducted via highperformance liquid chromatography using UV detection and gas chromatography with mass selective detection. Furthermore, these compounds were analysed in serum and synthetic urine with concentrations between 5 and 100 ng/mL. In this case, a solid-phase extraction method served for sample preparation prior to quantification by liquid chromatography with electron spray ionization tandem MS. Methods were subject to validation and recovery rates were determined.
Fourier transform mass spectrometry enables molecular measurements for the most complex scenarios. This achievement is based on the acquisition of time domain signals that, once transformed into frequency space and subsequently mass spectra, provide spectra with the highest levels of mass resolving power. Due to technical and large-scale funding limitations, the current state of the art is largely hindered by the availability of superconducting magnets that provide a maximum of 21 T. To enable next-generation measurements of elevated mass resolving power and throughput, FTMS experimentalists must continually consider novel mass analyzer cell designs and ion detection schemes. Here, an initial demonstration of hexapolar frequency multiple detection (3 Omega) is provided in the context of MALDI mass spectrometry imaging. This experiment provides a substantial challenge to emerging MS technologies where samples lack the simplification afforded by the coupling of separations and molecular targets can vary substantially in spectral intensity within and between scans. Experiments conducted at 14.5 T have provided the means to baseline resolve standard lipid isotopologues and mass interferences in model organism tissues down to 2.4 mDa with provided mass resolving powers of 1.275 million at m/z 400 and mass accuracies below 200 ppb. These measurement capabilities extend towards m/z 900, at the high end commonly observed for most lipid MALDI experiments, even though mass resolving powers are reduced to 550,000. Concurrently, the ability to add confidence for MS1-only molecular assignments is extended by more routine observations of isotopic fine structure to complement the provision of high mass accuracy.
We describe a new setup aimed at generating neutral atom beams within the low-energy ion beam facility at IUAC. The arrangement consists of a new chamber designed for neutral beam production using gas or thin carbon foils. An electrostatic separator is employed to eliminate the residual ions that may accompany the neutrals along the original trajectory. A channeltron is aligned with the beam trajectory to measure the flux of neutral particles. Additionally, the setup integrates a pre-existing Time of Flight measurement system, an electrostatic analyzer for the post interaction projectile beam, complemented by a position-sensitive detector positioned off-center. A concise overview of the distinct components of the setup is outlined in this paper. Neutral hydrogen and argon beams have been successfully generated using the present setup in an energy range of 25-150 keV and the energy range can be extended up to 400 keV in future.The relative yield of multi-ionization events induced by hydrogen atom (H0) collision with atomic targets, namely argon (Ar) and helium (He), as well as the molecular target nitrogen (N2), is measured across an energy range from 25 to 150 keV. To interpret the role of electron in H-atom collisions, analogous measurements were conducted for proton impact under identical experimental conditions.
The advent of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) instruments equipped with collision reaction cells (CRCs) facilitates interference removal/mitigation via online gas phase separations. This approach has proven effective for high intensity ion beams measured on Faraday collectors; however, it has been observed that introduction of gas in the CRC can result in significant background signals relative to the more sensitive ion counters. These backgrounds hinder use of these instruments for low level concentration and isotopic ratio measurements when employing a reaction gas. This work directly evaluates the effect of gas purity on backgrounds of CRC-MC-ICP-MS instruments. Introducing high-purity research grade O2 (99.999%) into the CRC produces complex background spectra with intensities >104 cps observed at most masses across the measured mass range (7-300 m/z). Some features of the observed spectra (i.e., positive mass defects) can be attributed to molecular compounds comprised of significant hydrogen. Additionally, some specific molecular species can be identified (i.e., MoOxHy+) and appear to be derived from molybdenum rods comprising the CRC. Further purifying the gas reduces the intensity of these backgrounds by several orders of magnitude, to <102 cps in many cases, and reduces complexity of the resulting spectra. This reduction in background appears to be in part driven by removal of impurities (i.e., H2O) from the gas. This work demonstrates that additional purification of reaction gases prior to introduction into the CRC significantly reduces backgrounds detected, potentially expanding the utility of CRC-MC-ICP-MS for making low level measurements using inline gas phase ion separations.
Single-quadrupole mass spectrometry remains an underexploited yet highly accessible option for neurochemical analysis. In this study, an analytical workflow was optimized to enhance the sensitivity of a single-quadrupole instrument operated in Selected Ion Monitoring (SIM) mode for the targeted detection of 17 neurotransmitters and related metabolites. Systematic optimization of in-source dissociation, ionization mode, and source parameters enabled substantial signal gains, particularly under HILIC conditions, where intensity increases reached up to 40-fold for highly polar analytes. The optimized method yielded sub-nanomolar detection limits for most compounds, with limits of detection in the picogram range for several neuroactive molecules, for instance 40 pg and 1 pg/injection for dopamine and octopamine respectively. Fragment-ion-based discrimination allowed reliable differentiation of structural isomers, such as dopamine and octopamine, despite their identical precursor m/z. A proof-of-concept application was conducted on dissected ant brains, demonstrating that extremely small tissue samples can be quantitatively profiled for multiple biogenic amines using only a single-quadrupole detector. Although this instrumentation does not permit global metabolite coverage, the results show that, when properly optimized, it provides sufficient sensitivity and selectivity for targeted neurochemical analysis and approaches toward neurometabolomics. The approach thus offers a cost-effective alternative for laboratories lacking tandem MS systems and can be readily adapted to other species or biological matrices.
The performance of a quadrupole mass filter (QMF) is highly sensitive to deviations from ideal electrode geometry. In this work, we investigate the effect of small inward and outward tilting of cylindrical rods on the resolving power and transmission characteristics of a QMF. Such geometric perturbations introduce an axial variation in the radial confinement potential, resulting in Mathieu parameters that vary along the ion trajectory. To examine this effect, the ion stability diagram is computed using a Runge-Kutta (RK45) method with axially-varying Mathieu parameters. The modified stability region exhibits shift and contraction depending on the magnitude and nature of rod inclination. The evolution of higher-order field components, particularly the dodecapole term, is analyzed along the axial direction. Ion trajectory simulations are performed using SIMION to evaluate the corresponding changes in QMF transmission characteristics in the first stability zone of operation. While simulations at fixed operating conditions indicate a transmission-resolution trade-off at small tilting angles leading to an apparent enhancement in resolving power, analysis at constant peak transmission reveals that even slight deviations from the parallel configuration degrade the overall resolving power. These results highlight the critical role of minute geometric imperfections in QMF operation and provide insights into tolerance limits and design optimization for improved mass filter performance.
A procedure for the qualitative analysis of pinacolyl methylphosphonic acid (PMPA), a degradation product from the nerve agent soman (GD), is presented. The protocol involves the derivatization of PMPA with benzyl trichloroacetimidate resulting in its benzylation under neutral conditions, a desirable attribute in the presence of other base-sensitive analytes. The method was found to perform well in the detection of this Schedule 2 chemical, spiked at low concentrations, in three different test matrices, two soils and one liquid, featured in different Organisation for the Prohibition of Chemical Weapons (OPCW) proficiency tests.
The vibrational energy levels of the two isotopomers adopted by the I & oline;center dot HDO ion-molecule complex occur such that the OH(D) stretching fundamentals span its dissociation energy, thus enabling a spectroscopic investigation of the dynamics displayed by a system prepared in the vicinity of the dissociation threshold. This regime is explored using infrared photoexcitation of the mass-selected complexes cooled in a cryogenic radiofrequency (Paul) ion trap. Survey spectra are obtained at modest resolution using two-color, IR-IR photodissociation with nanosecond lasers to establish the level structure and unimolecular decay dynamics of the v = 1 and 2 levels of the bound OH(D) oscillator. The v = 1 levels are prepared by fixed frequency excitation in the trap and the absorption spectra arising from this excited state are probed by photofragmentation of the complex with a second pulsed IR laser after a variable delay time (0 to 20 ms). The transitions to levels above the dissociation threshold for I & oline; + HDO formation are observed to be sharp (similar to 5 cm(-1) FWHM). At low pressure, the bound OD (v = 1) population relaxes very slowly (similar to 3 ms), consistent with resonant fluorescence in the IR. The collisional quenching rate constants of this level by the He buffer gas were estimated to be on the order 3 & times; 10(-12) cm(3)/s based on a crude Stern-Volmer analysis. The rotational fine structure and linewidths (less than or similar to 0.01 cm(-1) FWHM) arising from transitions of the non-bonded OH stretch fundamental of the OD-bound isotopomer that lies just above the dissociation energy are determined using single photon photodissociation by excitation of the 10 K ions with a single-frequency, CW IR laser in the ion trap.
Progress in mass spectrometry is driven not only by incremental improvements in existing spectrometer designs but also by the development of new physical methods of ionization, principles of mass-to-charge separation, and techniques for ion detection. In this work, we investigate the possibility of creating a highly sensitive mass analyzer based on the relatively unexplored principle of isotrajectory optics. Algorithms for the numerical simulation of isotrajectory particle-optical systems are proposed, and the corresponding software has been developed. The developed software was validated using test problems with known analytical solutions, confirming the consistency of the modeling approach with the principles of isotrajectory dynamics. Numerical simulations revealed, for the first time, the presence of second-order angular focusing in an isotrajectory mass analyzer. This focusing property ensures high sensitivity of the device. Finally, the main performance parameters of the proposed analyzer, including its luminosity and mass resolving power, were determined.
