scholarly journals Quantitative oscillator strengths for ionic fragmentation of C 1s and O 1s excited CO

2004 ◽  
Vol 82 (6) ◽  
pp. 1052-1060 ◽  
Author(s):  
A CO Guerra ◽  
J B Maciel ◽  
C C Turci ◽  
R C Bilodeau ◽  
A P Hitchcock
Keyword(s):  
Mass Spectrometry ◽  
Kinetic Energy ◽  
Cross Sections ◽  
Time Of Flight ◽  
Branching Ratios ◽  
Ion Pair ◽  
Oscillator Strengths ◽  
Ion Trajectory ◽  
Ion Fragmentation ◽  
Flight Mass Spectrometry

Ionic photofragmentation of carbon monoxide following carbon 1s and oxygen 1s excitation has been measured quantitatively with tuned synchrotron light and time-of-flight mass spectrometry using a Wiley–McLaren apparatus modified with an additional ion lens for improved quantitative performance. The sensitivity of the apparatus to kinetic energy and angular distribution effects has been characterized for selected lens settings through ion trajectory simulations and experimental measurements. Three distinct modes of the added lens have been identified (focus, defocus, and maximum). The focus mode has the least sensitivity to details of the angular and ion kinetic energy distribution and, therefore, is the best mode for measuring quantitative partial ion and ion-pair yields. The defocus mode has the most sensitivity to angular and kinetic energy distributions and, therefore, is the mode that provides the most information about the kinematics of photofragmentation. Branching ratios for ion and ion-pair production in all positive ion fragmentation channels were recorded from 280 to 330 eV (C 1s) and from 520 to 570 eV (O 1s) in the "focus" mode. Quantitative oscillator strengths were derived by combining these branching ratios with absolute total ion yield spectra. The results are compared to literature values.Key words: CO, time-of-flight mass spectrometry, inner-shell excitation, quantitative oscillator strengths, cross sections.

scholarly journals Studying in vitro metabolism of the first and second generation of antisense oligonucleotides with the use of ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry

2020 ◽  
Vol 412 (27) ◽  
pp. 7453-7467
Author(s):  
Anna Kilanowska ◽  
Łukasz Nuckowski ◽  
Sylwia Studzińska
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Liver Microsomes ◽  
Time Of Flight ◽  
Ion Pair ◽  
In Vitro Metabolism ◽  
Detection Methods ◽  
Ion Pair Chromatography ◽  
Flight Mass Spectrometry

Abstract The aim of the present investigation was the analysis and identification of antisense oligonucleotide metabolism products after incubation with human liver microsomes regarding four different oligonucleotide modifications. Separation and detection methods based on the use of liquid chromatography coupled with quadrupole time-of-flight mass spectrometry were developed for this purpose. Firstly, the optimization of mass spectrometer parameters was done to select those which ensure the highest possible sensitivity of oligonucleotide analysis. This step was conducted for two chromatographic modes—ion pair chromatography and hydrophilic interaction liquid chromatography—due to their common application in oligonucleotide analysis. Based on sensitivity results, ion pair chromatography coupled with mass spectrometry was selected for the separation of model oligonucleotide mixtures in order to verify its selectivity for N-deleted metabolite separation. Next, the developed method was applied in the examination of oligonucleotides in vitro metabolism. First, wide optimization of incubation parameters was conducted including the concentration of the reaction buffer components. Obtained results indicated that both 3′-exonucleases and 5′-exonucleases contributed to the biotransformation of oligonucleotides. Moreover, it may be concluded that the number of metabolites depends on oligonucleotide modification and consequently its resistance to enzymatic attack. Thus, the number of the oligonucleotide metabolites decreased with the decrease of the resultant polarity of oligonucleotide caused by chemical modification.

Methane ice photochemistry and kinetic study using laser desorption time-of-flight mass spectrometry at 20 K

2015 ◽  
Vol 17 (26) ◽  
pp. 17346-17354 ◽  
Author(s):  
J.-B. Bossa ◽  
D. M. Paardekooper ◽  
K. Isokoski ◽  
H. Linnartz
Keyword(s):  
Mass Spectrometry ◽  
Kinetic Study ◽  
Time Of Flight ◽  
Laser Desorption ◽  
Effective Rate ◽  
Branching Ratios ◽  
Ionization Time ◽  
Flight Mass Spectrometry ◽  
Pure Methane ◽  
First Time

Laser Desorption Post-Ionization Time-Of-Flight Mass Spectrometry is used to perform a systematic kinetic study on the pure methane photolysis in the condensed phase at 20 K and provides for the first time effective rate constants and branching ratios for primary processes leading to CH3, CH2, and CH radicals upon irradiation by VUV light in the 120–170 nm domain.

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