International Journal of Mass Spectrometry最新文献

In this study, a new method has been developed and, the method has been validated to analyze dimethyl sulfate (DMS) which known as a genotoxic impurity. DMS has been detected in trace levels within the drug substance pantoprazole sodium sesquihydrate using the derivatization method. Triethylamine has been used as derivatization reagent. Due to the highly polar nature of the derivatization product, which is a quaternary ammonium ion, a polar retention Hilic column has been used for chromatographic separation. The Waters QDA detector has been used in the single ion recording (SIR) mode at m/z 116 for the detection of the quaternary ammonium ion. In this study, the recovery rates have been achieved within the range of 96.46–105.98%. The LOD has been determined as 1.94E-07 mg/mL, and the LOQ has been determined as 6.46E-07 mg/mL. From the results, it can be said that the improved method in this study, would enables fast and reliable solutions for routine quality control analyses for DMS in API companies that especially is producing PSS.

In preparation of space-change studies a MagneTOF detector is evaluated for bunches with a wide range of ion numbers. The detector is calibrated based on the comparison between single-ion counting and ion-bunch-signal integration. This allows to determine up to several ten thousands of ions in a bunch with a FWHM of about $700\mathrm{ns}$, the integrated signal of which increases linearly with the ion number. Furthermore, this detector limit can be circumvented using transmission-limiting elements in front of the detector. Based on this, ion bunches are investigated up to several million ions, which are prepared with a linear Paul trap. Thus, in addition to the MagneTOF detector this trap is characterized with respect to its space-charge limits at low potential-well depth.

Multi-reflection time-of-flight (MR-ToF) analyzers must control the transversal ion dispersion, orthogonal to the axis of reflection, conventionally via periodic refocusing, or more recently the shaped electrode structure adopted by the Astral analyzer. In principle, the complexity of the dispersion control on every oscillation may be avoided at a cost of a smaller number of oscillations, during which the dispersion doesn't exceed the limit of unrecoverable overlap. A method of dispersion control has been demonstrated experimentally and in simulation, whereby the ion beam is configured by a long focus trans-axial lens made of a pair of quasi-elliptical plates mounted above and below the ion beam, in order to optimize the spatial spread of the ions at a distant detector. The collimation concept was shown to effectively control beam expansion. For experimental confirmation, a prototype Astral analyzer was modified, and resolving power above 70k demonstrated.

Recent advancements in high-resolution ion mobility spectrometry-mass spectrometry (IMS-MS) have enabled the separation of isotopologues and isotopomers based on their mass distribution-based isotopic shifts (i.e., changes in center of mass and moments of inertia). To better understand the fundamental nature of these isotopic shifts, we investigated whether they were additive in nature by introducing varying isotopic substitutions (e.g., ¹³C, ²H/D, and ⁸¹Br) through either hydrogen deuterium exchange or permethylation. From there, we measured the relative arrival times between light and heavy isotopologues with high-resolution cyclic ion mobility separations. Globally, we observed that the isotopic shifts were approximately additive in nature regardless of the molecule system or specific isomer studied. Furthermore, we discovered that additivity occurs in the isotopic shifts irrespective of the absolute shift, potentially indicating this observation may be more global in nature. We believe that our findings will serve to better understand the fundamental nature of mass distribution-based isotopic shifts and will inform theoretical ion mobility calculations in the future.

We report the installation of a new infrared ion spectroscopy platform at the free-electron laser facility FELIX, based on a Bruker SolariX Fourier Transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with a trapped ion mobility spectrometry (TIMS) stage. The instrument allows one to record infrared multiple-photon dissociation (IRMPD) spectra for mass and mobility selected ions, produced by a range of ion sources. We describe two strategies to achieve consistent overlap between the laser beam and the ion packet. Removing the original ECD cathode significantly enhanced the IR transmission and the overlap with the ion cloud, resulting in improved IRMPD yield per pulse. Enhancement of the photodissociation yield is observed when multiple pulses are used, as there is negligible collisional deactivation in the ultra-high vacuum trapping region of the ICR cell. We compare IRMPD spectra recorded on the new platform with IRMPD spectra of the same species recorded on one of our 3D-quadrupole ion trap platforms. We demonstrate the instrument’s performance using a sample containing a mixture of two trisaccharides. Mobility selection allows us to record individual IR spectra for the two isomeric species. This multi-modal platform, encompassing liquid chromatography, ion mobility spectrometry, ultra-high resolution (tandem) mass spectrometry, infrared ion spectroscopy (and soon also mass spectrometry imaging), is available to users at the FELIX facility.

This study investigates the unimolecular reactions of glutathione complexes with alkali metal cations in the gas phase through sustained off-resonance irradiation collision-induced dissociation and examines their structures using a combination of infrared multiphoton dissociation spectroscopy and computational techniques. Under soft CID conditions, glutathione complexes with charge-dense cations such as Li⁺, Na⁺, and K⁺ show significant fragmentation of glutathione, while complexes with heavier cations, Rb⁺ and Cs⁺, primarily undergo loss of glutathione. This behavior is attributed to the stronger non-covalent binding between smaller metal cations and glutathione, which competes with the dissociation thresholds of covalent interactions within the peptide complex. Using CREST, a tool for determining trial structures which were submitted to density functional theory calculations, a thorough investigation of the conformational space revealed many possible structures, including pentacoordinated structures for the Na⁺ and K⁺ complexes, as well as tetra-tri-, bi-, and monocoordinated structures along with zwitterionic structures for all metal cation/GSH complexes. For all alkali metal cation complexes, the thermodynamically most stable structures were found to be tetracoordinated A-type structures where the metal cation is bound to the amine nitrogen and three of the carbonyl oxygens—all except O2, the amide between glycine and cysteine. These computed infrared spectra for these lowest energy complexes were also consistent with the experimental vibrational spectra in the fingerprint region. Based on relative energies and the comparison of computed and experimental infrared spectra in the fingerprint region, the tetracoordinate A-type structures are concluded to be the dominant forms of the [M(GSH)]⁺ complexes in the gas phase.