European Journal of Mass Spectrometry最新文献

Butyl-terminated poly(2-vinylpyridine) (P2VP), C₄H₉(C₇H₇N)_nH, is evaluated for use as an external and internal mass calibrant in positive-ion matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS). P2VP oligomers covering the m/z 450-4500 range are employed to calibrate a time-of-flight (TOF) mass spectrometer in linear and reflector mode, an ion mobility-quadrupole-time-of-flight (IM-Q-TOF) mass spectrometer, and a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The proton affinity of P2VPs introduced by the numerous pyridyl groups leads to the almost exclusive formation of [M + H]⁺ ions with common acidic matrices like α-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB) as well as with the non-acidic and aprotic matrices 1,8-dihydroxy-10H-anthracen-9-on (dithranol) and 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malonitrile (DCTB). This prevalence of [M + H]⁺ ions evenly spaced at Δ(m/z) = 105.0578 renders butyl-terminated P2VP oligomers as convenient mass calibrants. The mass accuracies achieved across various m/z ranges with different mass analyzers and modes of operation are evaluated by using established standard compounds. Results as obtained by internal or external calibration are presented. Further, the compilation of mass reference lists tailored to suit the respective analyzer modes is discussed and those reference files are provided.

We have developed here a superior methodology based on high-resolution mass spectrometry for screening and fragmentation analysis of gangliosides extracted and purified from the human motor cortex . The experiments, conducted on a nanoelectrospray Orbitrap mass spectroscope in the negative ion mode, allowed the discrimination in the native mixture extracted from human motor cortex of no less than 83 different gangliosides, which represents the highest number of structures identified so far in this brain region. The spectral data, acquired in high-resolution mass spectrometry mode with a remarkable sensitivity and an average mass accuracy of 4.48 ppm, also show that the gangliosidome of motor cortex is generally characterized by species exhibiting a much higher degree of sialylation than previously known. Motor cortex was found dominated by complex structures with a sialylation degree ≥3, exhibiting long saccharide chains, in the G1 class. Fucogangliosides and species with the glycan chain elongated by either O-acetylation and/or acetate anion attachments were also detected; the later modification was for the first time discovered in this brain region. Of major significance is the identification of hepta and octasialylated species of GS1 and GO1 type, which are among the structures with the longest oligosaccharide chain discovered so far in the human brain. In the last stage of research, tandem mass spectrometry performed by higher energy collision dissociation provided structural data documenting the occurrence of GT1b (d18:1/20:0) isomer in the human motor cortex.

Joseph John Thomson is best known for detecting two isotopes of neon within cathode ray tubes that lay the foundation of the field of mass spectrometry. He was awarded the 1906 Nobel Prize in Physics for the discovery of the electron and for his work on the conduction of electricity in gases in the same devices. He is less known for his strong religious beliefs and his interest in psychical research and the paranormal. Thomson served as a member of the Society for Psychical Research for over 50 years and even became its Vice President. During this time, he attended a number of séances and demonstrations by professed psychics and mediums. This article traces those who influenced his interest in the paranormal, from Balfour Stewart to Lord Rayleigh and William Crookes. It reports and illustrates his beliefs and experiences investigating the paranormal in his own words.

The photoionization and dissociative photoionization of toluene have been studied using synchrotron radiation vacuum ultraviolet light with photon energy in the range of 8.50-25.50 eV. The ionization energies (8.82 eV) and double ionization energies (23.80 eV) of toluene as well as the appearance energies for its major fragments C₇H₇⁺ (11.17/10.71 eV), C₆H₅⁺ (13.73 eV), C₅H₆⁺ (13.58/12.50 eV), C₅H₅⁺ (16.23 eV), C₄H₅⁺ (15.64 eV), C₄H₄⁺ (16.10 eV) and C₄H₃⁺ (17.11 eV) are determined, respectively by using photoionization efficiency spectrometry. With the help of experimental and theoretical results, seven dissociative photoionization channels have been proposed: C₇H₇⁺ + H, C₆H₅⁺ + CH₃, C₅H₆⁺ + C₂H₂, C₅H₅⁺ + C₂H₂ + H, C₄H₅⁺ + C₃H₃, C₄H₄⁺ + C₃H₄ and C₄H₃⁺ + C₃H₄ + H. In addition, the geometries of the intermediates, transition states and products involved in these photoionization and dissociative photoionization processes have been performed at the B3LYP/6-311++G(d, p) level. The mechanisms of dissociative photoionization of toluene and the intermediates and transition states involved are discussed in detail. Generally speaking, the experimental results are in agreement with theoretical calculations in this work and published literature results. Especially the mechanisms of dissociative photoionization to C₄H₅⁺, C₄H₄⁺ and C₄H₃⁺ were discussed for the first time in this work. This investigation may provide useful information on understanding the photoionization and dissociative photoionization of toluene.

The analytical value of peaks arising by a proximity effect in the electron ionization mass spectra of benzanilides has been established by examining the spectra of numerous examples of general structure XC₆H₄NHCOC₆H₄Y. Significant [M-X]⁺ signals are observed only when X = Cl, Br, I or CH₃O in the 2-position. The presence of strong [M-X]⁺ signals, but negligibly weak [M-Y]⁺ peaks, even when the C-Y bond would be expected to break more readily than the C-X bond, indicates that these diagnostically useful signals do not arise by simple cleavage. Similarly, the presence of an appreciable [M-Cl]⁺ signal, but no [M-Br]⁺ signal, in the spectra of representative examples of 4-Br-2ClC₆H₃NHCOC₆H₄Y, reveals that loss of a substituent from the 2-position occurs much more rapidly than fission of a weaker bond to a substituent in the 4-position. These trends are interpreted in terms of cyclization of the ionized 2-substituted benzanilide, followed by elimination of the substituent originally in the 2-position, to form a protonated 2-arylbenzoxazole.

Bortezomib (BT) is a reversible inhibitor of proteasome which is used in the treatment of hematological cancers. To study the degradation behavior, BT was subjected to acidic, basic, neutral, photolytic, oxidative and thermal degradation conditions as per ICH guideline Q1A (R2). A gradient HPLC method has been developed for separating all the degradation products formed under various degradation conditions on Waters XBridge C₁₈ column (150 mm × 4.6 mm × 3.5 µm) using the mobile phase composed of ammonium formate and acetonitrile. A total of six degradation products were formed in various stress conditions and these were separated identified, and characterized using high performance liquid chromatography in combination with electrospray ionization tandem mass spectrometric studies.

The increasing use of electronic nicotine delivery systems (ENDS) is of concern due to multiple emerging adverse health effects. Most analyses of the harmful chemicals of ENDS have targeted metals or carbonyls generated by thermal decomposition of carrier liquids such as propylene glycol. However, new complex compounds not routinely identified and with unknown health consequences could be formed. ENDS aerosol samples were collected by the direct aerosol droplet deposition method. Untargeted analysis was performed using Orbitrap mass spectrometry with high mass accuracy. We identified more than 30 "features" in the aerosol characterized by pairs of the mass-to-charge ratio "m/z" of the compound and the retention time. We identified several compounds containing nicotine and propylene glycol (NIC-PG), whose abundance relative to nicotine increased along with vaping power used. On the basis of the prediction by the Environmental Protection Agency Toxicity Estimation Software Tool, these compounds exert developmental toxicity. In addition, a nitrogen-containing compound, likely tributylamine (a known lung irritant), was identified based on the molecular weight. This compound has not been previously identified in ENDS e-liquids and aerosols. ENDS produce not only small toxic compounds such as aldehydes, but also large complex toxic compounds such as NIC-PG. Predicted development toxicity for NIC-PG is concerning for fetal development in pregnant women who use ENDS, children exposed to secondhand or thirdhand ENDS aerosols, and teenage ENDS users whose brains are still developing. The strong positive association between NIC-PG levels and ENDS power output supports regulating high-powered ENDS.