ion pair separation
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2021 ◽  
Author(s):  
Shiyue Fang

The ion pair thermal model for MALDI MS is described. Key elements of the model include thermal desorption and ionization, strong tendency to neutralization via ion pair formation and proton transfer in the gas phase, thermal equilibrium, overall charge neutral plume, and thermal energy assisted free ion generation via ion pair separation by ion extraction potential. The quantities of ions in the solid sample and in the gaseous plume are estimated. Ion yields of different classes of molecules including peptides, nucleic acids, permanent salts and neutral molecules are estimated at the macroscale and single ion pair levels. The estimated ion yields are close to experimentally observed values under certain assumptions. Explanations of several observations in MALDI MS such as mostly single-charged peaks, improvement of spectra by ammonium cation, and ion suppression are provided. We expect that the model can give insights for the design of new conditions and systems for improving the sensitivity and resolution of MALDI MS and improving its capability and reliability to analyze large biomolecules.


Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2150
Author(s):  
Justyna Jurek-Suliga ◽  
Zbigniew Grobelny ◽  
Sylwia Golba ◽  
Hubert Okła ◽  
Katarzyna Bednarczyk

Polyether-pentols (PEPOs) were synthesized from glycidyl ethers and butylene oxide with the application of tripotassium salts of 2,2,6,6-tetrakis(hydroxymethyl)cyclohexanol (HMCH) activated 18C6 for ring-opening polymerization (ROP). The construction of the applied initiator system reflects the ability of crown ether to influence the degree of ion-pair separation with an increased activating effect. As a result formation of bi- or trimodal polymers was observed with molar masses in the range of (Mn = 1200–6000). The observed multi-fraction composition is prescribed to the formation of ionic aggregates with different reactivities during polymerization. The mechanism of the studied processes is discussed. The obtained PEPOs served for a crosslinked PUR synthesis, for which the hydrogen bond index for coupling of hard segments was calculated. Additionally, the range of phase separation was calculated that was higher for PUR-containing aromatic rings as the substituent.


2017 ◽  
Vol 23 (62) ◽  
pp. 15633-15637 ◽  
Author(s):  
Eric A. Marro ◽  
Eric M. Press ◽  
Tapas K. Purkait ◽  
Daniel Jimenez ◽  
Maxime A. Siegler ◽  
...  

CrystEngComm ◽  
2009 ◽  
Vol 11 (7) ◽  
pp. 1204 ◽  
Author(s):  
Giuseppe Gattuso ◽  
Anna Notti ◽  
Sebastiano Pappalardo ◽  
Melchiorre F. Parisi ◽  
Tullio Pilati ◽  
...  

2008 ◽  
Vol 63 (8) ◽  
pp. 923-928 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Elena V. Klimkina

The 13C, 27Al and 11B NMR spectra of tri(tert-butyl)alane, AlBut3, and of the corresponding borane, BBut3, respectively, were examined in order to determine the magnitude of the coupling constants 1J(27Al,13C) = 94±5 Hz and 1J(13C,11B) = 52±2 Hz by measurement of the line widths of the 13C NMR signals and of the relaxation rates of the quadrupolar 27Al and 11B nuclei. This is the first example of 1J(27Al,13C) determined for a monomeric trialkylalane. In addition, the coupling constants were calculated by DFT methods (B3LYP) using the 6-311+G(d,p) basis set. The 1H, 13C and 27Al NMR spectra of lithium tetra(tert-butyl)alanate, Li[AlBut4], were measured under various conditions. Ion-pair separation in THF revealed the expected patterns for 27Al-13C spin-spin coupling across one and two bonds as well as for the three-bond 27Al-1H spin-spin coupling.


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