Ion Mobility Research Articles

Structural complexity of glyphosate and aminomethylphosphonate metal complexes.

Small differences in the structure and subsequent reactivity of glyphosate complexes can have a highly consequential impact due to the enormous quantities of glyphosate used globally. The gas phase metal speciation of glyphosate and its abundant metabolite, aminomethylphosphonic acid (AMPA), were determined using cross-platform electrospray ionisation ion mobility mass spectrometry. Monomeric [M + L - H]+ complexes, and both larger, and/or higher order clusters formed with divalent metals (M = Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Cu2+, and Zn2+; and L = glyphosate and AMPA). Complexation occurred at more than one ligand donor site for [M + L - H]+, resulting in multidentate complexes. The type of complex depended on M, with central positions maximizing the interactions of the M with donor sites of the L preferred. The isomers were separated by ion mobility and experimental collisional cross sections (N2CCSexp) were derived for all isolated species. An energy threshold DFT approach located the structural families and potential lowest energy forms; these were found to be consistent with confirmed condensed phase (reported crystal structures) and gas phase structures (via infrared multiple photon dissociation, IRMPD). Theoretical nitrogen collisional cross sections (N2CCScalc) of these confirmed structures tended to underestimate the N2CCSexp for both [M + glyphosate - H]+ and [M + AMPA - H]+ complexes. Underestimation ranged between 1-20%, and was not uniform between species. By comparison, helium collisional cross sections (HeCCSexp and HeCCScalc) were in better agreement (within 1-3%). These findings suggest further refinements are needed to collisional cross section modelling for metal containing species, in particular for nitrogen drift gas.

Effect of Fluorine Segments in Fluoropolymer Matrix on the Properties of Gel Polymer Electrolytes

AbstractPolymer quasi‐solid electrolytes have been paid widely attention in account of their outstanding advantages in safety, flexibility, viscoelasticity and film formation. Fluoropolymer is used as matrix of gel electrolytes not only has high electrochemical stability, but also facilitates the dissociation of lithium salts owning to the strong electron‐absorbing C−F groups, which makes it a very promising choice for the further development of gel electrolytes. Due to the different sites of C−F bonds, their activity is also diverse, which results in the difference of the mobility of lithium ions and the LiF composition of SEI film on the surface of lithium metal anode. As a result, distinct fluorine‐containing gel polymer electrolytes are prepared by in‐situ polymerization of two different monomers, HFMA and TFMA. Compared with −CF3 on terminal group in TFMA, the gel electrolyte polymerized with HFMA whose C−F group with stronger electronegativity is at the intermediate carbon site, as polymer matrix has better performance. The ionic conductivity achieves 7.02×10−3 S cm−1 at room temperature, and the assembled batteries have a capacity retention rate of 91 % after 200 cycles of 1 C. Our research has laid a solid theoretical foundation for the further development of quasi‐solid electrolyte.

Sn-Position-Resolved Quantification of Aminophospholipids by Isotopic N,N-Dimethyl Leucine Labeling and High-Resolution Ion Mobility Mass Spectrometry.

Aminophospholipids (APLs), composed of phosphatidylethanolamines (PEs) and phosphatidylserines (PSs), are vital components of mammalian cell membranes and lipoproteins, participating in both homeostasis and cellular signaling. Their structural changes, including the permutation of fatty acid connectivity (sn-positions), due to dysfunctional metabolic processes have been linked to many diseases. However, the accurate quantification of APLs with unambiguous fatty acyl assignment through routine label-free LC-MS/MS lipidomic analysis remains a major challenge. In this study, we explore the functionalization of the free primary amine groups of APLs using amine-reactive isotopic N,N-dimethyl leucine (iDiLeu) and employ high-resolution ion mobility MS (IM-MS) to develop a novel method for sensitive discernment and accurate quantification of APL sn-isomers. With high-resolution demultiplexing (HRdm) providing IM resolving power >200, labeled sn-isomeric pairs of APLs (ΔCCS ≈ 1%) demonstrate excellent, near baseline separation. In addition to greatly enhanced sensitivity, 5-plex iDiLeu labeling enables the construction of an internal 4-point calibration curve and therefore absolute quantification of APL sn-isomers in a single run. This strategy enabled precise annotation and quantification of 239 APLs including 60 pairs of sn-isomers in the mouse cortex. Additionally, we were able to find ratio changes in multiple APL sn-isomer pairs between wild type and APP/PS1 Alzheimer's disease (AD) model mice at different ages, indicating their strong correlation to AD progression. This strategy could provide universal utility in unraveling the alteration of APL sn-isomers, which have long been considered as the "dark matter" of traditional lipidomic analyses, leading to more precise elucidation of molecular mechanisms of various diseases.

Biophysical mechanism of animal magnetoreception, orientation and navigation

We describe a biophysical mechanism for animal magnetoreception, orientation and navigation in the geomagnetic field (GMF), based on the ion forced oscillation (IFO) mechanism in animal cell membrane voltage-gated ion channels (VGICs) (IFO-VGIC mechanism). We review previously suggested hypotheses. We describe the structure and function of VGICs and argue that they are the most sensitive electromagnetic sensors in all animals. We consider the magnetic force exerted by the GMF on a mobile ion within a VGIC of an animal with periodic velocity variation. We apply this force in the IFO equation resulting in solution connecting the GMF intensity with the velocity variation rate. We show that animals with periodic velocity variations, receive oscillating forces on their mobile ions within VGICs, which are forced to oscillate exerting forces on the voltage sensors of the channels, similar or greater to the forces from membrane voltage changes that normally induce gating. Thus, the GMF in combination with the varying animal velocity can gate VGICs and alter cell homeostasis in a degree depending, for a given velocity and velocity variation rate, on GMF intensity (unique in each latitude) and the angle between velocity and GMF axis, which determine animal position and orientation.

Asymmetric Imidazolium-Based Ionic Liquid Crystal with Enhanced Ionic Conductivity in Low-Temperature Smectic Phases

We report the synthesis and characterization of a novel asymmetric imidazolium-based ionic liquid crystal (ILC) dimer exhibiting stable smectic phases over a wide temperature range, including room temperature. This unique molecular structure, combining two distinct mesogenic cores, reduces packing density, which enhances ion mobility and achieves high ionic conductivity in the smectic phase (0.1 mS cm−1 at 40 °C). Electrochemical impedance spectroscopy (EIS) confirmed improved ionic conductivity at lower temperatures, along with a stable electrochemical window of ±3 V. Application as a solid-state electrolyte in an electrochromic device demonstrated effective switching behavior and reversible redox cycles. These findings suggest that this asymmetric imidazolium-based ILC is a viable candidate for advanced electrochemical applications due to its structural stability and anisotropic ionic pathways.

Probing the Intramolecular Folding of Nucleic Acids with Native Ion Mobility Mass Spectrometry: Strategies and Caveats.

The goal of native mass spectrometry is to obtain information on noncovalent interactions in solution through mass spectrometry measurements in the gas phase. Characterizing intramolecular folding requires using structural probing techniques such as ion mobility spectrometry. However, inferring solution structures of nucleic acids is difficult because the low-charge state ions produced from aqueous solutions at physiological ionic strength get compacted during electrospray. Here we explored whether native supercharging could produce higher charge states that would better reflect solution folding, and whether the voltage required for collision-induced unfolding (CIU) could reflect preserved intramolecular hydrogen bonds. We studied pH-responsive i-motif structures with different loops, and unstructured controls. We also implemented a multivariate curve resolution procedure to extract physically meaningful pure components from the CIU data and reconstruct unfolding curves. We found that the relative unfolding voltages reflect to some extent, but not always unambiguously, the number of intramolecular hydrogen bonds that were present in solution. Reaching phosphate charging densities over 0.25 makes it easier to discriminate between structures, and the use of native supercharging agents is thus essential. We also uncovered several caveats in data interpretation: (1) when different structures (for example the i-motif with and without hairpin) unfold via different pathways, the unfolding voltages do not necessarily reflect the number of hydrogen bonds, (2) unstructured controls also undergo unfolding, and the base composition influences the unfolding voltage, (3) changing the solution pH also unexpectedly changed the unfolding voltage, and (4) the ion mobility patterns become more complicated when two structures are present simultaneously, such as an i-motif and a harpin, because of opposite effects on the collision cross section upon activation.

Displacement of extracellular chloride by immobile anionic constituents of the brain's extracellular matrix

AbstractGABA is the primary inhibitory neurotransmitter. Membrane currents evoked by GABAA receptor activation have uniquely small driving forces: their reversal potential (EGABA) is very close to the resting membrane potential. As a consequence, GABAA currents can flow in either direction, depending on both the membrane potential and the local intra and extracellular concentrations of the primary permeant ion, chloride (Cl). Local cytoplasmic Cl concentrations vary widely because of displacement of mobile Cl ions by relatively immobile anions. Here, we use new reporters of extracellular chloride (Cl−o) to demonstrate that Cl is displaced in the extracellular space by high and spatially heterogenous concentrations of immobile anions including sulfated glycosaminoglycans (sGAGs). Cl−o varies widely, and the mean Cl−o is only half the canonical concentration (i.e. the Cl concentration in the cerebrospinal fluid). These unexpectedly low and heterogenous Cl−o domains provide a mechanism to link the varied but highly stable distribution of sGAGs and other immobile anions in the brain's extracellular space to neuronal signal processing via the effects on the amplitude and direction of GABAA transmembrane Cl currents. imageKey points Extracellular chloride concentrations in the brain were measured using a new chloride‐sensitive organic fluorophore and two‐photon fluorescence lifetime imaging. In vivo, the extracellular chloride concentration was spatially heterogenous and only half of the cerebrospinal fluid chloride concentration Stable displacement of extracellular chloride by immobile extracellular anions was responsible for the low extracellular chloride concentration The changes in extracellular chloride were of sufficient magnitude to alter the conductance and reversal potential of GABAA chloride currents The stability of the extracellular matrix, the impact of the component immobile anions, including sulfated glycosaminoglycans on extracellular chloride concentrations, and the consequent effect on GABAA signalling suggests a previously unappreciated mechanism for modulating GABAA signalling.

Synthesis and characterization of a copper-based metal–organic framework and its application in microextraction and determination of chlorpyrifos by ion mobility spectrometry

This study describes an innovative method for the microextraction and determination of chlorpyrifos, utilizing a newly synthesized copper-based metal–organic framework (MOF) with 3,3ʹ-thiodipropionic acid as the ligand. This approach offers a sensitive and reliable solution for the ultra-trace determination of chlorpyrifos in various matrices, highlighting its potential for broader environmental and food safety applications. To minimize environmental impact, a hydrothermal method was chosen for MOF synthesis. The MOF was fully characterized using FT-IR, X-ray diffraction, FESEM-EDX, BET, zeta potential analysis, and XPS; and integrated into a dispersive solid-phase microextraction (DSPME) technique, paired with ion mobility spectrometry (IMS) for chlorpyrifos detection. The DSPME procedure has been optimized for extraction efficiency, minimal solvent use, and low absorbent consumption. A low detection limit of 0.65 ng mL−1 was observed and validated along with a linear detection range of 1.0–400.0 ng mL−1 as the result of this optimization. Experiments with water, pear fruit, and soil samples demonstrated the method’s practicality and superior performance compared to existing techniques, showcasing its potential for real-world applications.

Analytical method for predicting interference in ion mobility spectrometric detection of drug compounds with phthalates

In ion mobility spectrometry (IMS), ions are distinguished by their mobility through a gas, which depends on their size, shape, and charge. Ions with very similar reduced ion mobility (Ko) values are not separated. This technique is widely used for the onsite detection of drug compounds. However, the presence of phthalates can interfere with IMS-based detection of drug compounds because some of them may have Ko values similar to those of drug compounds. In this study, the interference of phthalates in the IMS detection of drug compounds was investigated using drug compounds and phthalates in the molecular weight range of 134–335 g mol−1. The relationships between Ko and the m/z value, collision cross section (CCS), maximum cross section (CSmax), and minimum cross section (CSmin) of the product ions were examined. The CSmax and CSmin values were calculated from the energy-minimized structures of the ions. It was found that the m/z, CCS, and CSmax values were not closely related to the Ko value. However, the CSmin values showed a strong correlation with the Ko values, exhibiting excellent linear relationships with R2 values of 0.997 for the drug compounds and 0.990 for the phthalates. By comparing the CSmin values of drug compounds and phthalates, the probability of their peaks overlapping in the IMS spectra can be determined. For chemicals that are difficult to identify, the overlap of the peaks with the target chemicals can be determined using their CSmin values.

Continuous fiber printing of a modular heater for ion mobility spectrometry

Ion mobility spectrometry (IMS) is a powerful analytical method for separating and detecting gaseous substances like volatile organic compounds (VOCs). It is highly versatile, used both as a standalone technique and in combination with chromatographic methods for pre-separation or mass spectrometry for complex matrix analysis. This study explores the use of an advanced 3D printing technology to print a heater for an IMS-device.A continuous fiber printer, commonly used to enhance the mechanical properties of printed objects, was used to create a customized heating element by embedding a copper wire within the polymer matrix during the printing process. Cyclic olefin copolymer (COC) was chosen as the matrix material due to its analytical properties, such as low off-gassing and higher thermal stability, compared to the more commonly used polylactic acid (PLA).The 3D printed heater was incorporated into a drift tube ion mobility spectrometer, and its performance was evaluated by analyzing the separation of various ketones. The results show that the 3D printed heater effectively controlled the temperature within the drift tube, improving the resolving power of overlapping peaks.This study shows the potential of 3D printing technology to improve fabrication and functionality of IMS devices. The flexibility in design and material selection afforded by 3D printing not only enhances the analytical performance of IMS but also allows for customization and rapid prototyping of other analytical instruments or laboratory devices.

Novel selective ionic liquid membrane-coupled microfluidic chip for heavy metal separation and analytical strategies

The development of new low-cost, highly selective and efficient methods for the separation and detection of heavy metal ions in aqueous environments is of great importance for water safety and biological health. In this study, a novel ion separation membrane was prepared for the separation of copper ions in cadmium ion detection solution. Compared with the commercial membrane, the ion mobility was increased by 64.02 %, and further separated by selective complexation of thiacalix[4]arene-p-tetrasulfonate (TCAS), and the separation factor for Cu/Cd reached 34.66. This allowed Cd to be detected preferentially, and reduced the interference of other ions in the detection. The joint electric field environment was regulated to separate the organics and reduce the interference to the detection. The sensing performance was enhanced by modifying the screen-printed electrodes. The proposed sensing platform allows for simultaneous pre-processing and detection and has a detection limit of 0.19 μg-L−1 (S/N = 3) for Cd2+.

New NASICON-type phosphates, KNbM(PO4)3 (M = Ti, V), exhibiting a reversible alkali metal intercalation

The NASICON framework is an attractive object for designing polyanion electrode materials for metal-ion batteries. Two new NASICON-structured (S.G. R-3c) niobium phosphates KNbTi(PO4)3 (a = 8.4307(1) Å, c = 23.3955(4) Å, V = 1440.11(5) Å3) and KNbV(PO4)3 (a = 8.4892(1) Å, c = 23.3042(4) Å, V = 1454.45(3) Å3) were synthesized by the Pechini sol–gel method. Rietveld refinement revealed the potassium atoms occupy only the A(1) 6-fold antiprismatic site in both structures. Nb K-edge XANES measurements confirmed the presence of Nb5+ in KNbV(PO4)3 and the mixed-valent Nb5+/4+ in KNbTi(PO4)3 phosphates. Electrochemical measurements showed that both compounds deliver the initial discharge capacity of 110–120 mAh g−1 at a C/10 rate in the Na-half cell. KNbV(PO4)3 also maintains a reversible K+ intercalation at about 1.5 V vs. K+/K with a significant hysteresis (∼0.35 V at a C/10 rate) indicating a sluggish K+ diffusion. The mobility of alkali metal ions within the framework of new phosphates is discussed in terms of bond valence site energy calculations.

The effect of energy modality on tissue identification from surgical smoke by differential ion mobility spectrometry

Surgical smoke analysis offers a way to provide assisting information to the surgeon intraoperatively, which can be potentially used to assess cancer tumor margins in surgical oncology and alert the operator of accidental organ injuries caused by electrosurgical (ES) instruments. Surgical smoke content is affected by the energy instrument it is produced by. Classification of surgical smoke by differential ion mobility spectrometry (DMS) was evaluated with 6 porcine tissue types and 5 energy instruments. Instruments consisted of mono- and bipolar instruments, ultrasonic shears and a –blade. Machine learning was used to classify tissues by training binary classifier linear discriminant analysis (LDA) to distinguish a marked tissue class from the rest. The greatest binary classification accuracies were obtained with the monopolar instruments and the lowest with the bipolar instrument, 93.5 % and 77.5 % respectively. The analysis of surgical smoke with DMS is possible with a variety of energy instruments, however with varying performance. This implies that DMS based tissue identification is generalizable across different surgical instruments and surgical specialties.

Quasi-longitudinal whistler propagation in presence of finite ion response

In recent studies, quasi-longitudinal whistlers propagating along the resonance cone were identified to develop a steep density structure as a result of longitudinal resonant excitations in the upper-hybrid regime that are nonlinearly modified. The question of whether the ion response to these resonant whistlers in the lower hybrid regime, shared by them with ion excitations, leads to a stronger resonant coupling of quasi-longitudinal whistlers to electrostatic fluctuations remains unexplored and addressed by incorporating finite ion mobility (i.e., departure from mi→∞ limit) in present coherent quasi-longitudinal whistler simulations. At moderate angles, the ion response shows modification of lower hybrid ion excitations at the stage of evolution where the longitudinal electrostatic field of both modes grows comparable. The ratio of electron density fluctuation associated with whistler and plasma density fluctuation associated with ion response is, however, recovered to be small and confirmed analytically. In propagation along the resonance cone at high density, the ion fluctuations approach lower hybrid resonance without density steepening. Excited at equal wave numbers, they complement the longitudinal electrostatic field of the quasi-longitudinal whistlers. At higher densities, steep sharp electron density fluctuations are found recurrent and in equilibrium with the coherent lower-hybrid ion density structures.

Study on the change of the oil-paper insulation’s AC conductivity characteristics based on dielectric response in frequency domain

Oil-immersed power equipment (transformers and high voltage bushings) are key components of power systems. Oil-paper insulation has endured complex and harsh operating conditions when used as a primary insulation system, so it is essential to determine the insulation state of oil-paper insulation system to ensure a stable operation for the power grid. The oil-paper insulation’s conductivity behavior can effectively characterize the degree of insulation deterioration. However, the relationship between the alternating current (AC) and direct current (DC) conductivity behavior for oil-paper insulation systems is still unclear in current research, resulting in limitations in the traditional evaluation model’s application. Therefore, this paper uses oil-paper insulation materials under different aging to carry out relevant research about the changing features of the complex AC conductivity under different test temperature environments. The influence of oil-paper insulation aging, test temperature, and excitation frequency on the complex AC conductivity is verified. Considering the correlation between low-frequency AC conductivity and DC conductivity, the frequency range of AC conductivity is extended by means of frequency temperature and conductance double translation. The temperature dependence of the AC conductivity behavior is defined over a wide frequency test range. The relaxation polarization process dominated the AC conductivity variation law is obtained. The impact of experimental temperature and insulation aging on the cumulative characteristic parameters of AC ionic mobility is clarified. This study theoretically corrects the traditional calculation model for AC conductivity of oil-paper insulation. The bias in conductivity calculations caused by only considering a single relaxation polarization process is eliminated. The conductivity model that can characterize multiple relaxation polarization processes in the dielectric is established. This model provides theoretical support for the later assessment of oil-paper insulation state depending on conductance behavior.

Unveiling exceptional conduction mechanism and high proton conductivity in amorphous electrolyte for advanced ceramic fuel cells

The requirement of high ion conductive material working at low temperatures is highly demanding in fuel cells. This study explains a groundbreaking advancement in ceramic fuel cells by exploring the potential of amorphous Sm0.3Al0.7-oxide and the proton conduction mechanism of amorphous oxides. Opposite to conventional crystalline electrolytes, amorphous electrolytes showed superior ion conduction. To study the detailed mechanism of ion conduction, amorphous Sm0.3Al0.7-oxide was selected which exhibited an exceptional proton conductivity of 0.17 S/cm and a power density of 1100 mW/cm2 at 550 °C, significantly surpassing traditional electrolyte materials. Using advance characterization techniques, a new approach has been proposed to provide the reasons for the high conductivity of amorphous materials, which entails a complete mechanism that describes how disordered structure and disoriented grain boundaries facilitate efficient proton conduction by reducing energy barriers and enhancing ionic mobility. Also, it has been described how the high enthalpy and the high energy state of amorphous materials are suitable for enhancing proton conduction. This study aims to clarify why amorphous materials are promising candidates for future fuel cell applications, facilitating significant advancements in SOFC and PCFC technologies and paving the way for more efficient and sustainable energy solutions.

Li<sub>3-2x</sub>Nb<sub>x</sub>Cr<sub>2-x</sub>(PO<sub>4</sub>)<sub>3</sub> Complex Phosphates with the Nasicon Structure: Synthesis and lon Conductivity

One of the main trends in the development of metal-ion batteries is the transition to lithium anodes, the safe use of which is impossible without replacing liquid membranes with solid membranes, primarily inorganic ones. Lithium-niobium-chromium phosphates with calculated compositions Li3–2xNbxCr2–x(PO4)3 (x = 0.95, 1.00, 1.05) were obtained by solid-state synthesis and characterized by XRD analysis and impedance spectroscopy. The obtained complex lithium-niobium-chromium phosphates with the NASICON structure crystallize in hexagonal modification. The lattice parameters of the synthesized materials decrease with increasing chromium content. The material of composition Li1.1Nb0.95Cr1.05(PO4)3 (3.10–5 S/cm at 25 °C) possesses the highest ionic conductivity and the lowest activation energy, which indicates a greater mobility of lithium ions by the interstitial mechanism even in the region of its own disorderliness.

Influence of ion mobility and electrode structure effects on supercapacitors with CaO, MgO, and SiO2

Influence of ion mobility and electrode structure effects on supercapacitors with CaO, MgO, and SiO2

Effect of ionic wind on the sample distribution in corona discharge ion mobility spectrometry

Ionic wind generated during corona discharge (CD) can significantly influence the airflow field within Ion Mobility Spectrometry (IMS), yet its impact is often overlooked. This study delves into the impact of ionic wind on sample distribution, emphasizing the need to balance reactant ion density and ionic wind intensity, which leads to sample dilution. To mitigate this issue, an axial injection mode employing a hollow needle was proposed, thereby improving the sensitivity and recovery performance of CD-IMS. As a result, the limit of detection of dimethyl methylphosphonate (DMMP) monomer is lowered from 15 ppbv to 5 ppbv. Furthermore, this technique was successfully applied to the detection of lithium battery electrolyte leaks, with carbonate concentrations as low as 10 mg/L or 1 nL being detected within 5 s. Such findings underscore the technique's applicability for swift and sensitive monitoring of battery safety.

Studying Structural Details in Complex Samples: II. High Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) Coupled to High Resolution Tandem Mass Spectrometry (MS/MS).

The elucidation of structural motifs in extremely complex mixtures is very difficult since the standard methods for structural elucidation are not capable to provide significant information on a single molecule. The best method for the analysis of complex mixtures is ultrahigh resolution mass spectrometry, but the utilization of this method alone does not provide significant information about structural details. Here, a combination with a separation method is necessary. While chromatography is a well-established technique, it has some disadvantages in regard to the separation of complex mixtures, as often no separation of individual isomers is possible. Therefore, here the combination of an ion mobility separation with ultrahigh resolution mass spectrometry is evaluated. As a sample matrix, crude oil is used because it is an excellent matrix to develop new analytical techniques on complex samples. Crude oil is the most complex natural sample known, but only little information is available on the structural identity or functionalities due to a high number of structural isomers or isobars. A lab-built APPI/APLI-FAIMS source was revised to optimize ion transmission and used to follow up on the ion mobility of crude oil constituents after photoionization. An MS/MS approach using collision-induced dissociation (CID) was used to elucidate structural motifs of the transmitted isomers.