Structure, anion, and solvent effects on cation response in ESI-MS

Omari, Isaac; Randhawa, Parmissa; Randhawa, Jaiya; Yu, Jenny; McIndoe, J. Scott

doi:10.26434/chemrxiv.7723226.v1

Cited by 2 publications

(2 citation statements)

References 30 publications

(35 reference statements)

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“…Many factors impact the quantitative determination of analyte concentrations via ESI MS. Ionization efficiency, desolvation, and detector response depend on the analyte molar mass and molecular shape along with the nature of the solvent and counterion. 44 Herein, the ESI MS samples from catalytic polymerization reactions were prepared identically and comparisons were made between the relative ion counts of 5 vs 6 observed in the same sample. Therefore, the solvent and anion differences are unlikely to impact the accuracy of these results.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Nature of the Active Catalyst in the Hafnium-Pyridyl Amido-Catalyzed Alkene Polymerization

et al. 2021

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We report the true nature of active catalysts in the polymerization of 1-octene catalyzed by the racemic hafnium-pyridyl amido cation (I). Chromophore quench-labeling (CQL) studies reveal that only ca. 50% of the catalyst actively participates in the polymer chain growth. The mass spectral analysis of the pyridine ligands obtained postpolymerization demonstrates that about one-half of the ligand is modified by the insertion of 1-octene into the Hf–naphthyl bond of I. The fraction of octyl-modified ligands correlates with active-site counts, as determined by the correlation of CQL studies and the mass spectral analysis of ligands during in situ activation experiments. The analysis of reaction kinetics and active-site counts were obtained using two different activation methods: (1) activation with the ammonium salt [HNMe(C18H37)2][B(C6F5)4] followed by the polymerization of 1-octene or (2) activation with [Ph3C][B(C6F5)4] followed by 1-octene polymerization in the presence of differing amounts of NMe(C18H37)2. These studies indicate that different diastereomers of activated rac-1 exhibit vastly different polymerization properties; one diastereomer (Ia) initiates rapidly, while the other diastereomer (Ib) initiates much more slowly. Accordingly, the cause of 50% active-site counts in the 1-catalyzed polymerization of 1-octene is stereochemical in origin. Related achiral hafnium-pyridyl amido complexes exhibit much higher active-site counts, thus further supporting the stereochemical origin of reduced active-site counts.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Nature of the Active Catalyst in the Hafnium-Pyridyl Amido-Catalyzed Alkene Polymerization

et al. 2021

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“…82 More recently, studies have shown differences in ionization efficiency for fixed-charge organic ions depending on their origin from protic or aprotic solvent systems. 94 Thus, a sound understanding of the effects of different solvent systems on the various ionization processes described here could allow the tailoring of cVSSI techniques for specific comparative and structural -omics analyses.…”

Section: ■ Results and Discussionmentioning

confidence: 97%

Physicochemical Property Correlations with Ionization Efficiency in Capillary Vibrating Sharp-Edge Spray Ionization (cVSSI)

Jayasundara

DeBastiani

et al. 2020

J. Am. Soc. Mass Spectrom.

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The relative contributions to ionization efficiency by three molecular chemical properties have been examined for field-free and field-enabled capillary vibrating sharp-edge spray ionization (cVSSI) using mass spectrometry (MS) analysis. Ion intensities have been recorded for model compounds under each operational ionization mode as well as for aqueous and nonaqueous (methanol) solvent systems. Multiple regression analysis suggests that for field-free cVSSI, ion intensity is mostly associated with the log of the base dissociation constant (pK b) and proton affinity (PA) for both aqueous and methanol solutions. Comparatively, for field-enabled cVSSI using aqueous solutions, the dominant factor correlated with ion intensity is the log of the partition coefficient (log P). To a lesser degree, this is observed for methanol solutions as well. For ESI, pK b is the dominant factor associated with ion signal levels from methanol and aqueous solutions. These results are supported by studies conducted on two different mass spectrometers employing different cVSSI emitter tips. The relationship of ion intensity and pK b in ESI is supported by multiple studies; however, the shift to other chemical properties with the addition of cVSSI suggests the possibility that a different (or combinations of) ionization mechanism(s) may be operative for these ionization modes. These results are briefly considered in light of the different ESI mechanisms.

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Structure, anion, and solvent effects on cation response in ESI-MS

Cited by 2 publications

References 30 publications

Nature of the Active Catalyst in the Hafnium-Pyridyl Amido-Catalyzed Alkene Polymerization

Nature of the Active Catalyst in the Hafnium-Pyridyl Amido-Catalyzed Alkene Polymerization

Physicochemical Property Correlations with Ionization Efficiency in Capillary Vibrating Sharp-Edge Spray Ionization (cVSSI)

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