International Journal of Mass Spectrometry最新文献

The antiProton Unstable Matter Annihilation experiment (PUMA) at CERN aims at investigating the nucleon composition in the matter density tail of radioactive as well as stable isotopes by use of low-energy antiproton-nucleon annihilation processes. For this purpose, antiprotons provided by the Extra Low ENergy Antiproton (ELENA) facility will be trapped together with the ions of interest. While exotic ions will be obtained by the Isotope mass Separator On-Line DEvice (ISOLDE), stable ions will be delivered from an offline ion source setup designed for this purpose. This allows the proposed technique to be applied to a variety of stable nuclei and for reference measurements. For beam purification, the ion source setup includes a multi-reflection time-of-flight mass spectrometer (MR-ToF MS). Supported by SIMION® simulations, an earlier MR-ToF MS design has been modified to meet the requirements of PUMA. During commissioning of the new MR-ToF device with Ar⁺ ions, mass resolving powers in excess of 50,000 have been obtained after 150 revolutions, limited by the chopping of the continuous beam from an electron impact ionisation source.

The demand for analytical tools for the analysis of low-concentration volume-limited samples has driven researchers to explore new analytical approaches. Mass spectrometry excels at trace analysis due to its high sensitivity and specificity, whereas ambient methods simplify, or completely eliminate sample preparation. Herein, we report a triboelectric nanogenerator-coated blade spray ambient mass spectrometry (TENG-CBS MS) method for the extraction, elution, and ionization of volume-limited, low-concentration small molecule drug samples with minimum sample preparation. Using a TENG device as the CBS power supply, we show it is possible to extract and analyze drug samples in a pulsed fashion at sub-nanogram to picogram levels with good stability and reproducibility. A wide range of analytes polarities were tested. Results indicated this method could also be useful for the analysis of low-level analytes in precious, volume limited samples in a simple single step.

Methane and cyclopropane (c-C₃H₆) were reacted with Ru⁺ ions in a room temperature ion trap and the resulting products were identified using a combination of mass spectrometry, IR action spectroscopy, and density functional theory calculations. In the reaction with methane, no products with odd numbers of carbon atoms were located, whereas significant amounts of products with even numbers of carbon atoms were observed. We identified [Ru,2C,4H]⁺ as the Ru⁺ ion with an ethene ligand attached, and [Ru,4C,6H]⁺ as a Ru(η⁴-cis-1,3-butadiene)⁺ complex. The barrier toward formation of Ru(C₂H₄)⁺ + 2H₂ was calculated at the B3LYP/def2-TZVPPD level to be 0.80 eV above the energy of the ground state Ru⁺ (⁴F) + 2 CH₄ reactants. In the reaction of c-C₃H₆ with Ru⁺, we identified the dehydrogenation product [Ru,3C,4H]⁺ as Ru(η²-propyne)⁺, [Ru,2C,2H]⁺ as Ru⁺ with an ethyne ligand, and [Ru,5C,5H]⁺ as Ru(η⁵-c-C₅H₅)⁺ having a cyclopentadienyl ligand.

Using light generated by an infrared free electron laser, action spectroscopy was performed on doubly charged complexes of the metalated dipeptide histidyl-histidine (HisHis). Metal cations used were zinc, cadmium, and copper. Molecular dynamics and quantum-chemical calculations were used to screen a large number of conformers, whose theoretical infrared spectra were compared to the recorded action spectra of these metalated complexes. The zinc and cadmium spectra display dominant features associated with an iminol binding motif of the HisHis ligand, where the metal ion coordinates with both pros (π) nitrogens of the imidazole sidechains, the terminal carbonyl oxygen, and the backbone nitrogen for which the hydrogen ordinarily bound here has migrated to a carbonyl. The copper complex was difficult to assign to a single species, because a few predicted bands are absent from the experimental spectrum. The theoretical single point energies were also calculated for all structures examined, and DFT methods were found to describe the ion conformer populations in the case of the zinc and cadmium chelates better than the MP2 prediction.

Peptide/protein quantitation using mass spectrometry (MS) is advantageous due to its high sensitivity. Traditional absolute peptide quantitation methods rely on making calibration curves using peptide standards or isotope-labelled peptide standards, which are expensive and take time to synthesize. A method which can eliminate the need for using standards would be beneficial. Recently, we developed coulometric mass spectrometry (CMS) which can be used to quantify peptides that are oxidizable (e.g., those containing tyrosine or tryptophan), without using peptide standard. The method is based on electrochemical oxidation of peptides followed by MS measurement of the oxidation yield. However, it cannot be directly used to quantify peptides without oxidizable residues. To extend this method for quantifying peptides/proteins in general, in this study, we adopted a derivatization strategy, in which a target peptide is first tagged with an electroactive reagent such as monocarboxymethylene blue NHS ester (MCMB-NHS ester), followed with quantitation by CMS. To illustrate the power of this method, we have analyzed peptides MG and RPPGFSPFR. The quantification error was less than 5%. Using RPPGFSPFR as an example, the quantitation sensitivity of the technique was found to be 0.25 pmol. Furthermore, we also used the strategy to quantify proteins cytochrome C and β-casein with an error of 2–26 %.

Increasing the dimensionality of ion mobility (IM) presents an enticing opportunity to increase the information content and selectivity of many analyses. However, for implementations of IM that use constant electrostatic gradients to separate ions in a buffer gas, technical challenges have limited the adoption of the technique and number of dimensions within individual experiments. Here, we introduce a strategy to “reset” the potentials of ions between IM dimensions. To achieve this, mobility-selected ions are trapped between dimensions of IM, using a combination of RF and electrostatic fields, while the subsequent dimension of IM is devoid of any drift field. By applying an incremental voltage ramp, the potential of the trapping region is elevated, simultaneously establishing the drift field in the subsequent dimension of IM. The trapped ions are then released and separated. We measured similar arrival-time distributions of protein ions using this strategy and a method without potential resetting, suggesting that potential resetting can be performed without additional losses or activation of ions. The findings of those experiments were corroborated by ion trajectory simulations, which exhibited a very small changes in ion position and no significant changes in effective temperatures during potential resetting. Finally, we demonstrate that IM information can be preserved during potential resetting by selecting subpopulations of 9+ cytochrome c ions, resetting their potential, subjecting them to a second-dimension IM separation, and observing the retention of conformers within each subpopulation. We anticipate that this strategy will be useful for advancing flexible, multidimensional experiments on electrostatic IM instruments.

A coherent classification of electrospray axial regimes is provided based on non-linear fluid dynamics as revealed by spray current measurements and fast time-lapse imaging of the electrified meniscus. The classification includes two periodic (dripping, pulsating), two transient/chaotic (burst, astable), and two stationary (cone-jet, jetting) regimes. The dripping faucet phase diagram is described as a particular case of a more complex electrospray phase diagram. Spray current measurements and electrospray characteristic curves are presented as essential for the diagnosis of the electrospray operation and the transition between its various regimes. Reaching a consensus on regime nomenclature and a standardized approach to designate transitions between electrospray regimes is suggested. Finally, the effect of the electrospray operating regime on the mass spectrometer signal is briefly summarized.

Rapidly measuring protein thermodynamic stability is vital for understanding the fast protein folding and unfolding processes, involving many human disease-linked protein structures and the fulfilment of their dynamic functions. Heating-induced protein unfolding and conformational transformation studies may generate a variety of protein thermodynamic stability information such as protein melting temperature (T_m) and Gibbs free energy (ΔG). Previous nanoelectrospray ionization (nanoESI) - mass spectrometry (MS) has been interfaced with online heating device to achieve such information, but mostly operating in a slow mode in terms of temperature control. Herein, a new module for digital temperature control (DTC) was constructed and assembled into a nanoESI device, allowing for ultrafast measurement of thermodynamic stability. Typically, DTC can achieve whole-range heating-induced unfolding in 33 s with temperatures ranging from 0 °C to 99 °C but with jump step of 3 °C and deviation less than 1 °C. Notably, thanks to the advantage of ultrafast and precise temperature control, only less than 100 nL protein sample was consumed for each test, saving samples by more than 100 folds compared to previously reported temperature control devices. Besides, with the DTC-nanoESI-MS regime, we successfully achieved solution pH-dependent protein thermodynamics, which serves as first proof-of-concept demonstration for future applications even at a proteome level directly from limited biological samples.

In this study, we introduce the design, characterization, and application of an integrated thermal desorption corona discharge ionization (TD-CDI) device, which was developed for direct mass spectrometry (MS) analysis of drugs in solid or liquid samples. The structure and operational parameters of the TD module were optimized through simulation and experimental investigations. For the CDI module, a hollow needle was used as the discharge electrode and sample inlet, allowing self-aspiration and efficient ionization of the desorbed samples. The TD-CDI device was tested and characterized using different mass spectrometers, exhibiting satisfactory stability and quantitative performance. Owing to its compact structure, it can be coupled to a miniature MS instrument to implement rapid identification of various drugs in urine solutions.

Method of analysis with non-chiral chromatographic separation of isomeric forms of pyrethroids was developed for determination of five group of pyrethroid in lanolin, which is a natural product with wide applications in food, drug and cosmetic industry. Pyrethroid are used extensively for ectoparasitic treatments of sheep and find their way into sebaceous secretion of sheep as lanolin. The present study describes validation for developed method, including measurement of uncertainty (MU) at quantification limit of 0.05 μg/g. The method is based on modified matrix solid phase dispersion (MSPD) sample extraction steps and GC-MS/MS with multiple reaction monitoring (MRM) acquisition mode. The method was found to be linear over the analytical range of 0.05–1.0 μg/g, with acceptable coefficient of determination, (r² ≥ 0.99) for group calibration of 5 pyrethroids with LOD & LOQ of the method as 0.025 μg/g and 0.05 μg/g, for all the 12 isomeric forms of pyrethroid. Validation data showed method to be accurate with precision within the acceptable limits i.e. recoveries in the range of 73.5%–109% with less than 20% RSD for all the 5 group of pyrethroid. MU associated with results at LOQ shows that calculated expanded uncertainty at 95% confidence level for pyrethroids lies between 1.8 and 3.3 ng/g.