Ion Trap Research Articles

Applying Spatial Metabolomics To Investigate Age- and Drug-Induced Neurochemical Changes.

In an era when population aging is increasing the burden of neurodegenerative conditions, deciphering the mechanisms underlying brain senescence is more important than ever. Here, we present a spatial metabolomics analysis of age-induced neurochemical alterations in the mouse brain using negative ionization mode mass spectrometry imaging. The age-dependent effects of the acetylcholinesterase inhibitor tacrine were simultaneously examined. For ultrahigh mass resolution analysis, we utilized a Fourier-transform ion cyclotron resonance spectrometer. To complement this, a trapped ion mobility spectrometry time-of-flight analyzer provided high speed and lateral resolution. The chosen approach facilitated the detection and identification of a wide range of metabolites, from amino acids to sphingolipids. We reported significant, age-dependent alterations in brain lipids which were most evident for sulfatides and lysophosphatidic acids. Sulfatide species, which are mainly localized to white matter, either increased or decreased with age, depending on the carbon chain length and hydroxylation stage. Lysophosphatidic acids were found to decrease with age in the detailed cortical and hippocampal subregions. An age-dependent increase in the glutamine/glutamate ratio, an indicator of glia-neuron interconnection and neurotoxicity, was detected after tacrine administration. The presented metabolic mapping approach was able to provide visualizations of the lipid signaling and neurotransmission alterations induced by early aging and can thus be beneficial to further elucidating age-related neurochemical pathways.

Quantitative Analysis of Glutathione and Carnosine Adducts with 4-Hydroxy-2-nonenal in Muscle in a hSOD1G93A ALS Rat Model.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the dysfunction and death of motor neurons through multifactorial mechanisms that remain unclear. ALS has been recognized as a multisystemic disease, and the potential role of skeletal muscle in disease progression has been investigated. Reactive aldehydes formed as secondary lipid peroxidation products in the redox processes react with biomolecules, such as DNA, proteins, and amino acids, resulting in cytotoxic effects. 4-Hydroxy-2-nonenal (HNE) levels are elevated in the spinal cord motor neurons of ALS patients, and HNE-modified proteins have been identified in the spinal cord tissue of an ALS transgenic mice model, suggesting that reactive aldehydes can contribute to motor neuron degeneration in ALS. One biological pathway of aldehyde detoxification involves conjugation with glutathione (GSH) or carnosine (Car). Here, the detection and quantification of Car, GSH, GSSG (glutathione disulfide), and the corresponding adducts with HNE, Car-HNE, and GS-HNE, were performed in muscle and liver tissues of a hSOD1G93A ALS rat model by reverse-phase high-performance liquid chromatography coupled to electrospray ion trap tandem mass spectrometry in the selected reaction monitoring mode. A significant increase in the levels of GS-HNE and Car-HNE was observed in the muscle tissue of the end-stage ALS animals. Therefore, analyzing variations in the levels of these adducts in ALS animal tissue is crucial from a toxicological perspective and can contribute to the development of new therapeutic strategies.

Secondary metabolites of soybean seeds variety locus and their spatial arrangement, represented by laser microscopy

The purpose of this study is a detailed metabolomic analysis using tandem mass spectrometry of the soybean variety Locus, selected from the collection of the Federal Scientific Center for Agrobiotechnologies of the Far East named after A. K. Chaika», to identify both the polyphenolic composition of seeds and the determination of other chemical groups in the composition of the seed. Tandem mass spectrometry studies were further supported by visual data obtained for the first time using laser microscopy. The object of the study is the seeds of the soybean variety Locus, grown in 2022 at the field site of the soybean breeding laboratory of the Federal Scientific Center for Agrobiotechnologies of the Far East named after A. K. Chaika», located in the village of Timiryazevsky (near the city of Ussuriysk). Experiments were carried out on a CLSM-800 laser confocal microscope and mass spectrometry of biologically active substances on an amaZon SL ion trap. Laser microscopy made it possible to clarify in detail the spatial distribution of the content of phenolic acids, flavonols and anthocyanins in soybean seeds. The studies were able to convincingly show that soybean polyphenolic substances and, in particular, anthocyanins are spatially localized mainly in the soybean seed coat. High-performance liquid chromatography coupled with ion trap (tandem mass spectrometry) was used to identify target analytes in soybean seed extracts. Using tandem mass spectrometry, the presence of 59 compounds was identified, of which 35 compounds represent the group of polyphenolic compounds. 15 compounds were identified for the first time in soybean extracts of the Locus variety. These are flavones: apigenin, acacetin, cirsimaritin; tetrahydroxyflavone aromadendrin 7-O-rhamnoside; lignan medioresinol; coumarin tomentin and other polyphenolic compounds. The data obtained will help intensify future research on the development and production of new drugs, dietary supplements, food additives and various functional and specialized products containing targeted soybean extracts.

Narrowband 10-ps-class mode-locked erbium-doped fiber laser oscillator

We demonstrate a narrowband erbium-doped fiber (EDF) laser oscillator having a linear cavity based on the design of bulk laser oscillators mode-locked by a semiconductor saturable absorber mirror (SESAM) and out coupled by a fiber Bragg grating. The EDF laser oscillator has an average power of 7.06 ± 0.04 mW with a 3 dB bandwidth of 0.37 nm and a pulse duration of ∼12 ps at a repetition rate of 50.47 MHz. A pulse energy of ∼140 pJ is the highest ever reported in SESAM mode-locked EDF laser oscillators with a nearly Fourier-limited pulse duration demonstrating power scalability of a bulk laser and compactness of a nearly all-fiber laser. The repetition rate has a free-running fluctuation of only 312 Hz over 7 h of operation making it a promising light source for application to laser spectroscopy. The long pulse duration makes this EDF laser oscillator a suitable source for seeding a high-average-power amplifier using a large mode-area photonic crystal or tapered gain fiber without the need of pulse stretching. Moreover, this laser oscillator could be an alternative solution to the development of complicated bulk narrowband laser sources suitable for building an ion trap for application to quantum computing.

Tandem Mass Spectrometry Approaches for Differentiation and Quantification Pidotimod and Its Three Isomers in the Gas Phase.

Pidotimod is a chiral drug that possesses two chiral centers, resulting in three isomeric impurities (analytes, A). This study employs electrospray ionization ion trap mass spectrometry (ESI-MS) through collision-induced dissociation (CID) to investigate the chiral recognition of pidotimod and its three isomers to eliminate chromatographic separation. Three approaches were explored: (1) Protonated molecules in CID exhibited discriminative potential for diastereomers, with the ability to distinguish between S,S and R,R configurations, albeit with an Rchiral value of ~1.8. However, differentiation between R,S and S,R configurations was not achievable. (2) Alkali adductions (lithium and sodium) only discerned diastereomers. The Rchiral values of the diastereomers obtained from alkali adduct ions were significantly lower than those obtained from protonated ions. (3) Therefore, a third approach was used to address the challenge of distinguishing between R,S and S,R configurations, including the introduction of chiral references (ref) and transition metals (MII) to form metal-bound complexes [MII(A)(ref)-H]+. Additionally, we synthesized a novel ligand, 4-(N-tert-butoxycarbonyl [Boc]-L-prolinamido)phenol (denoted as ligand A), by modifying N-t-Boc-L-Pro with 2-aminophenol, which, in combination with CuII and NiII, enabled simultaneous differentiation of all four isomers. CuII complexes exhibited significant chiral selectivity between R,S and S,R configurations. Density functional theory calculations were performed to further elucidate the stereodynamic behavior and stoichiometry of these ions in the gas phase. These calculations revealed the interaction energy and coordination sites of the precursor ions in the gas phase, correlating well with MS/MS experiment results. Additionally, the logarithm of the CuII complexes' characteristic fragment ion abundance ratio demonstrated a strong linear relationship with enantiomeric excess (ee). This study presents a novel strategy for chiral drug quality control that eliminates chromatographic separation.

External Data Systems Enable Enhanced (and Sustainable) Fourier Transform Mass Spectrometry Imaging for Legacy Hybrid Linear Ion Trap-Orbitrap Platforms.

Legacy Fourier transform (FT) mass spectrometers provide robust platforms for bioanalytical mass spectrometry (MS) yet lack the most modern performance capabilities. For many laboratories, the routine investment in next generation instrumentation is cost prohibitive. Field-based upgrades provide a direct path to extend the usable lifespan of MS platforms which may be considered antiquated based on performance specifications at the time of manufacture. Here we demonstrate and evaluate the performance of a hybrid linear ion trap (LTQ)-Orbitrap mass spectrometer that has been enhanced via an external high-performance data acquisition and processing system to provide true absorption mode FT processing during an experimental acquisition. For the application to mass spectrometry imaging, several performance metrics have been improved including mass resolving power, mass accuracy, and dynamic range to provide an FTMS system comparable to current platforms. We also demonstrate, perhaps, the unexpected ability of these legacy platforms to detect usable time-domain signals up to 5 s in duration to achieve a mass resolving power 8× higher than the original platform specification.

Improved Measurement of the Differential Polarizability Using Co-Trapped Ions.

We present a novel approach for measuring the differential static scalar polarizability of a target ion utilizing a "polarizability scale" scheme with a reference ion co-trapped in a linear Paul trap. The differential static scalar polarizability of the target ion can be precisely extracted by measuring the ratio of the ac Stark shifts induced by an add-on infrared laser shed on both ions. This method circumvents the need for the calibration of the intensity of the add-on laser, which is usually the bottleneck for measurements of the polarizability of trapped ions. As a demonstration, ^{27}Al^{+} (the target ion) and ^{40}Ca^{+} (the reference ion) are used in this work, with an add-on laser at 1068nm injected into the ion trap along the trap axis. The differential static scalar polarizability of ^{27}Al^{+} is extracted to be 0.416(14)a.u. by measuring the ratio of the ac Stark shifts of both ions. Compared to the most recent result [Phys. Rev. Lett. 123, 033201 (2019)PRLTAO0031-900710.1103/PhysRevLett.123.033201], the relative uncertainty of the differential static scalar polarizability of ^{27}Al^{+} is reduced by approximately a factor of 4, to 3.4%. This improvement is expected to be further enhanced by using an add-on laser with a longer wavelength.

Ultra-narrow-linewidth hybrid-integrated self-injection locked laser at 780 nm

Narrow-linewidth lasers are essential across a wide range of applications, including classical and quantum sensing, trapped ion systems, position/navigation/timing systems, optical clocks, and microwave frequency synthesizers. In the visible and near-visible spectrum, low-noise lasers are particularly important for laser trapping and cooling techniques, which are vital for trapped ion quantum computing, sensing, and atomic clocks. In this context, our work showcases a hybrid-integrated narrow-linewidth laser that operates at 780 nm, achieving a self-heterodyne linewidth of 105 Hz. To validate the experimental results, we performed a numerical analysis that combines insights from a many-body theory applied to the gain region with a travelling-wave model to capture the laser dynamics. Our investigation further delves into how the linewidth of the self-injection locked lasers is influenced by the parameters of micro-ring resonators, aiming to assess the potential for achieving Hz-level integrated laser linewidths at 780 nm. This work not only demonstrates the technical feasibility of Hz-level narrow-linewidth lasers but also lays the groundwork for future explorations in the field.

Energy-Resolved In-Source Collison-Induced Dissociation for Isomer Discrimination.

While mass spectrometry remains a gold-standard tool for analyte detection, characterization, and quantitation, isomer differentiation is often a challenge. Tandem mass spectrometry is a common approach to increase the selectivity of mass spectrometry and energy-resolved measurements can provide further improvements. However, not all mass spectrometers, especially those that are very compact and affordable, are amenable to such experiments. For instance, single-stage mass spectrometers with soft ionization provide no dissociation information and quadrupole ion trap instruments with resonant excitation do not necessarily provide as informative of energy-resolved curves, for instance when extensive sequential dissociation is responsible for much of the "fingerprint". In-source collision-induced dissociation (IS-CID) is one approach to overcoming these barriers to exploit the analytical selectivity of energy-resolved CID without the need for additional instrumentation; this approach could broaden the reach of these selectivity gains to additional user bases (e.g., educational settings, field portable devices). Here, we specifically investigate energy-resolved IS-CID with the goal of (1) comparing between energy-resolved appearance curves measured with true tandem mass spectrometry on a quadrupole time-of-flight instrument and those obtained using IS-CID, (2) evaluating the approach as a means of differentiating isomers/isobar sets, especially those with similar dissociation patterns, and (3) exploring additional analytical considerations relevant to method development and implementation. This proof-of-concept work establishes the analytical potential of this approach, opening doors for future method development for specific applications.

Square Parametric Excitation: A Digital Resonant Method for the Quadrupole Ion Trap.

Digital ion trap technology is an alternate method for driving quadrupole ion traps and mass filters using variable frequency, fixed amplitude RF square waves in place of variable amplitude, fixed frequency RF sine waves. This technique offers some advantages such as an increase in the high mass analysis range by varying frequency and lower overall voltage requirements. Here, we present a complex square waveform developed for resonant parametric excitation in a quadrupole linear ion trap. Unlike traditional resonance methods, the driving RF square wave and auxiliary square wave are coupled using the same digital circuitry without the need for transformer coupling. In this work, we use this complex waveform to selectively excite the first order parametric resonances of ion motion. The square parametric excitation method presented here employs a simple and repetitive circuit design consisting of a low-voltage waveform generator followed by a series of high-voltage MOSFET switches. This design allows for resonance methods to be easily implemented in the all-digital quadrupole. The complex square waveform can perform the same useful functions as sine wave auxiliary signals, such as selective mass elimination and mass isolation. We also demonstrate that the mass resolution performance and S/N of our digital mass spectrometer is improved by applying the complex square waveform during ion ejection.

Reducing oxygen vacancies of MoO3 by polyaniline functionalization for stable and efficient inorganic tri-brominated perovskite solar cells

The photovoltaic performance of perovskite solar cells (PSCs) is closely dependent on the efficient carrier extraction and transport at the interface. Here, a polyaniline (PANI) functionalized MoO3 (PANI/MoO3) hole transport material (HTM) is exploited to perfect the interface between the perovskite layer and carbon electrode in all-inorganic CsPbBr3 PSCs. After functionalization with PANI, the p-type behavior and the hole mobility and conductivity of MoO3 are improved by reducing the oxygen vacancies, which boosts the hole extraction and transport, energy level arrangement at the interface of CsPbBr3 perovskite/(PANI/MoO3) HTM. Meanwhile, the PANI/MoO3 with rich C–N and N–H groups introduced by PANI passivates the ions trap states of perovskite films by the C–N⋯Pb2+ (Cs+) Lewis acid-base coordination and the N–H⋯Br− hydrogen bonding, leading to an effective suppression of non-radiative recombination for improved carrier extraction. As a result, the PANI/MoO3 HTMs-based CsPbBr3 PSCs obtain a remarkably increased power conversion efficiency of 10.41 %, in comparison with the efficiency of the original device (6.55 %). In addition, the unencapsulated device with PANI/MoO3 HTMs shows excellent long-term stability with 93.9 % maintenance of the initial efficiency after storing in air with 85 % relative humidity and at 85 °C for 30 days.

Conformation-Selective Ultraviolet-Ultraviolet Hole Burning Spectra of Ubiquitin Ions in a Cryogenic Ion Trap.

Understanding the structural variations of conformational isomers in proteins is crucial for elucidating protein folding mechanisms. Here, we present a novel method for obtaining conformation-selective ultraviolet (UV)-UV hole burning (HB) spectra of ubiquitin ions ((Ubi+zH)+z, z = 7-10) produced via electrospray ionization. Our approach involves binding multiple N2 molecules to ubiquitin ions ((Ubi+zH)+z(N2)m, m = 1-55) within a cryogenic ion trap. Upon exposure to UV irradiation, efficient fragmentation of (Ubi+zH)+z(N2)m occurs, primarily yielding bare (Ubi+zH)+z ions as fragments. The significant mass difference between the parent and fragment ions facilitates the acquisition of UV-UV HB spectra, which reveal the presence of at least two distinct conformers. Molecular dynamics simulations suggest that these conformers correspond to A-state structures, differing only in the interactions of a tyrosine residue with neighboring residues. Our findings underscore UV-UV HB spectroscopy of protein ions as a powerful tool for exploring diverse protein isomers.

Observation of the Infrared-Induced Structural Change in the Microscopic Hydrogen Bond Network of Phenol-Methanol Cluster Cations in a Cold-Ion Trap.

To gain insight into microscopic hydrogen bond networks, we measured ultraviolet photodissociation (UVPD) spectra of the phenol-methanol 1:3 cluster cation, [PhOH(MeOH)3]+ trapped in a variable temperature ion trap. At low temperatures, an isomer with a ring-type hydrogen bond structure dominates, whereas at higher temperatures the chain-type isomers become dominant due to the flexibility of their hydrogen bond structures. We also found a clear temperature dependence of the spectral features, such as band position and width. In addition to the above measurement, we observed the infrared (IR) induced isomerization of [PhOH(MeOH)3]+ to study the dynamical aspects of hydrogen bond networks. We succeeded in observing IR-induced isomerization from the ring to chain forms of [PhOH(MeOH)3]+ at low temperature. The isomerization was clearly identified as a change in the UVPD spectra. The time evolution of the UVPD spectra after IR excitation indicated that the IR-induced isomerization occurs within a nanosecond. The chain-type isomers produced by the IR-induced isomerization are then converted back to the ring-type form by collisions with cold He buffer gas in the trap. This backward isomerization proceeds with a time constant of 100 μs under our experimental conditions. In this study, we evaluated the temperatures of the chain isomers during the backward isomerization on the basis of the spectral features.

Sensitive and isotopic interference-free analysis of Sb using hydride generation-microwave plasma torch-mass spectrometry under ambient condition

A sensitive and isotopic interference-free analysis method for Sb was developed based on hydride generation-microwave plasma torch-mass spectrometry (HG-MPT-MS). Compared to the conventional ICP-MS, MPT coupled to an ion trap mass spectrometer enabled much “softer” ionization of Sb under ambient condition, which provided multi-detection modes and various ion forms, such as Sb+, SbO+, SbO2−, SbO++H2O and so on. These ion formations can be easily regulated by tuning capillary voltage and tube lens voltage, which facilitated elimination of isotopic interference during analysis, for instance the interference of 123Te on 123Sb could be effectively excluded by optimizing parameters of capillary voltage and tube lens voltage. The potential application of HG-MPT-MS for Sb isotope ratio analysis was also demonstrated, which could be determined in different forms, e.g., 123Sb/121Sb or 123Sb16O/121Sb16O. The value of 123Sb/121Sb was determined to be 0.75110 ± 0.00038 (2σ, n > 50). In addition, the detection limit, linearity and spike recovery were also studied. Overall, HG-MPT-MS performed equally well on detection limit (0.05 μg/L) with ICP-MS or HG-AFS. The linearity (R2 = 0.998) was checked in the concentration range of 10–500 μg/L. Spike recovery were evaluated with two soil samples, and the obtained spike recovery ranged 90–100 %. In general, HG-MPT-MS was expected to be a versatile tool for study the biochemical or geochemical behaviors of Sb and other hydride forming elements under ambient condition in a much simpler and more efficient way.

Study of three-stage high-resolution ion isolation for portable ion trap mass spectrometer

Portable ion trap mass spectrometers, especially for those with continuous atmospheric pressure interfaces, usually implement vacuum pumps with limited power for miniaturization, which leads to high vacuum pressures and reduced resolutions. In this study, two three-stage high-resolution ion isolation methods of SWIFT - AC frequency sweep - SWIFT and SWIFT - RF voltage ramp - SWIFT were proposed. Compared to the 2.8 m/z isolation resolution of the traditional SWIFT ion isolation method, higher isolation resolutions of 2.2 m/z and 1.5 m/z have been achieved by SWIFT - AC frequency sweep - SWIFT and SWIFT - RF voltage ramp - SWIFT ion isolation methods at an isolation efficiency of 40 %. In addition, our detailed experiments showed that all ion isolation methods can obtain higher isolation resolution under the conditions of lower vacuum pressure, higher isolation q value, and stronger axial confinement potential barrier, like which the mass resolution behaves. In order to inspect the effectiveness of the high-resolution isolation method, the control experiments of hair samples spiked with drugs had been conducted. The signal-to-noise ratio of O6-monoacetylmorphine can be improved by a factor of 2.4 using the SWIFT - RF voltage ramp - SWIFT ion isolation method. Our research results indicate that the performance of ion trap tandem mass spectrometry can be effectively improved by using the three-stage high-resolution ion isolation methods.

Programmable XY-type couplings through parallel spin-dependent forces on the same trapped ion motional modes

We propose and experimentally demonstrate an analog scheme for generating XY-type (Jijxσxiσxj+Jijyσyiσyj) Hamiltonians on trapped ion spins with independent control over the Jijx and Jijy terms. The Ising-type interactions σxiσxj and σyiσyj are simultaneously generated by employing two spin-dependent forces operating in parallel on the same set of normal modes. We analytically calculate the region of validity of this scheme, and provide numerical and experimental validation with Yb+171 ions. This scheme inherits the programmability and scalability of the Ising-type interactions with trapped ions that have been explored in numerous quantum simulation experiments. Our approach extends the capabilities of existing trapped ion quantum simulators to access a large class of spin Hamiltonians relevant for exploring exotic quantum phases such as superfluidity and spin liquids. Published by the American Physical Society 2024

A Gated TIMS FTICR MS Instrument to Decipher Isomeric Content of Complex Organic Mixtures.

Modern research faces increasingly complex materials with a constant need for new analytical strategies that can provide deeper levels of chemical insight. Ultrahigh resolution mass spectrometry (MS), particularly Fourier transform ion cyclotron resonance (FTICR) MS, has provided a robust analytical foundation. However, MS alone offers limited structural information. Here, we present the first implementation and results from an FTICR MS with fully integrated dual accumulation analysis with gated trapped ion mobility spectrometry (gTIMS) capability. The drastically extended charge capacity and parallel accumulation facilitate the analysis of complex mixtures. We achieved a high dynamic range of 4 orders of magnitude within a single FTICR acquisition event. Simultaneously, the valuable linear relationship between the TIMS elution voltage and reduced mobility was retained over a wide mobility range. Benchmarking the instrument performance with Suwannee River fulvic acid (SRFA) by variable ramp gTIMS analysis allowed separation and unambiguous assignment of different charge state distributions. Application to bio-oils has proven the capability to distinguish the isomeric diversity in these ultracomplex samples, while maintaining the expected FTICR MS resolving power and mass accuracy. Valuable information about the molecular distribution, isomeric diversity, and main molecular differences could directly be extracted within the analysis time of a classical "dilute and shoot" direct infusion experiment. The development of this fully integrated and flexible gTIMS with FTICR MS analysis possesses the potential to significantly change the current landscape of high-resolution mass spectrometric analysis of complex mixtures through the added insight of isomeric complexity afforded by TIMS. The exploration of the added IMS dimension promises transformative effects across diverse fields including energy transition, environmental studies, and biological research.

Synthesis and characterization of SBA-15 silica containing cyclam inside pores for capturing iron chloride: Analysis of interactions between ferrous chloride and cyclam in a system with strongly dispersed functional groups on the SiO2 surface

The use of the spatial structure of mesoporous silica combined with organic molecules opens up a wide range of possibilities in the field of separation of single atoms and the precise creation of their environment. Materials obtained in this way can find applications as single-atom catalysts (SAC) and in environmental applications in ion and molecule trapping processes. An example of such a material is silica of the SBA-15 type functionalized with cyclam (1,4,8,11-tetraazacyclotetradecane) anchored inside the pores with propyl chains. In this work, we present such a material containing 5% functional groups, additionally activated with iron(II) chloride, which was chelated by cyclam anchored inside the pores of silica. The presented nanocomposite has been thoroughly tested for its assumed molecular structure and stability. We compared it to a material containing only cyclam. The obtained results showed the high efficiency of the silica matrix with cyclam in the separation of single FeCl2 molecules and the correct molecular structure of the obtained material. The nanocomposite containing chelated molecules with iron showed good stability, while the structure of the material with cyclam alone collapsed with time.

Addressing a major interference in the quantification of psilocin in mouse plasma: Development of a validated liquid chromatography tandem mass spectrometry method

Psilocybin is a psychedelic compound found in some hallucinogenic “magic mushrooms”. Psilocin is the active metabolite of Psilocybin, and it is the subject of several studies for the treatment of psychological disorders, such as anxiety, depression, and post-traumatic stress disorder. As such, the pharmacokinetic properties of psilocin should be evaluated to ensure its safety and efficacy as part of the drug development process. Based on the previously published studies, reversed-phase liquid chromatography (LC) was tested for psilocin quantification. The analysis, however, showed a major interference in mouse plasma that was not, to the best of our knowledge, reported previously. We, therefore, aimed to identify and separate the interference, using various chromatographic columns, mobile phase conditions, and mass spectrometers (MS) instruments. Chromatographic separation was achieved on an ultra high performance liquid chromatography (UHPLC) system, and a quadrupole-linear ion trap equipped with an electrospray ionization (ESI) source was used in positive ion mode with multiple reaction monitoring (MRM). Several chromatographic conditions and column chemistries, including C-18 and Phenyl-hexyl were initially tested, and failed to separate the interference. Exact mass measurement and MS/MS analysis were used to determine the structure of the interfering compound, which was confirmed to be tryptophan. Using the identified structure of the interfering compound, a fast and reliable hydrophilic interaction liquid chromatography (HILIC)-MS/MS method was developed and validated, that was capable of separating psilocin from the interference while achieving a 0.5 ng/ml lower limit of quantification (LLOQ). The validated method was successfully applied to a pharmacokinetic study where psilocin was orally administered to C57BL/6 mouse subjects. Psilocin concentration in all the analyzed mouse plasma samples was successfully determined.

A simple numerical simulation model can elucidate the key factors for designing a miniaturized ion trap mass spectrometer

BackgroundMiniature ion trap mass spectrometer enables mass-to-charge ratio analysis of ions via quadrupole field in a low vacuum environment. It plays an important role in on-site detection due to its portability and specificity. In order to gain a deeper understanding of the analysis mechanism of miniature ion trap mass spectrometers, a quadrupole MS ion trajectory numerical simulation model (QITNS) is established in this paper for ions trajectory calculation under the action of quadrupole field, exciting field and neutral gas molecule collision. Compared with the existing methods, the model in this paper is simpler and more direct, which effectively explored the effects of dipole excitation and quadrupole excitation on ion manipulation under high background pressure. ResultsThe simulation results demonstrate that high RF amplitude, low auxiliary AC amplitude and quadrupole excitation can effectively improve the isolation resolution. Besides, it clarified the difference between the analysis mechanism of ion trap mass spectrometers under high background pressure (above 13.332 Pa) and absolute vacuum conditions. The relevant results are consistent with the conclusions of previous experiments and other theories, proving the applicability and accuracy of the proposed calculation model and solution method. SignificanceThis research bears the guiding significance for further understanding the mechanism of quadrupole mass spectrometry as well as designing and developing miniature mass spectrometers.