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Related Concept Videos

Electrospray Ionization (ESI) Mass Spectrometry01:12

Electrospray Ionization (ESI) Mass Spectrometry

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Higher molecular weight biomolecules are nonvolatile compounds that may decompose before ionizing or vaporizing during mass analysis with conventional electron impact ionization methods. Accordingly, electrospray ionization (ESI) is the favored method for vaporizing and ionizing biomolecules as it circumvents rapid fragmentation and enables the recording of mass signals for the entire biomolecule.
ESI utilizes electrical energy to transfer ions from the liquid phase of the sample into the...
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Chemical Ionization (CI) Mass Spectrometry01:21

Chemical Ionization (CI) Mass Spectrometry

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The molecular ion peak of a molecule in the mass spectrum provides vital information for molecular identification. However, conventional electron impact ionization can lead to the rapid dissociation of some molecular ions before they reach the detector. A milder ionization method is required to increase the lifetime of such ionized analyte molecules. Chemical ionization (CI) is a gas-phase protonation reaction useful for mass-analyzing analyte molecules that are easily protonated to yield the...
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¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)01:20

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

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When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
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Mass Spectrum: Interpretation01:24

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An unknown compound can be established by identifying the molecular ion peak in the mass spectrum. The molecular ion peak is often weak or absent due to the predominance of fragmentation in high-energy electron beams. In such cases, a soft-energy electron beam can be used to scan the spectrum to enhance the intensity of the molecular ion peak. Additionally, chemical ionization, field ionization, and desorption ionization spectra are used to obtain a relatively intense molecular ion peak.To...
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Ion-Exchange Chromatography01:09

Ion-Exchange Chromatography

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Ion-exchange chromatography, or IEC, is a technique for separating ions based on their affinity for the stationary phase. The stationary phase is a cross-linked polymer resin with covalently attached ionic functional groups. The functional groups can be either positively charged (cation exchangers) or negatively charged (anion exchangers). A cation exchanger consists of a polymeric anion and active cations, while an anion exchanger is a polymeric cation with active anions. The choice of...
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Polyprotic Acids03:38

Polyprotic Acids

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Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are:
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Determination of the Gas-phase Acidities of Oligopeptides
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Negative electrospray ionization via deprotonation: predicting the ionization efficiency.

Anneli Kruve1, Karl Kaupmees, Jaanus Liigand

  • 1University of Tartu , Institute of Chemistry, Ravila 14a, Tartu 50411, Estonia.

Analytical Chemistry
|April 16, 2014
PubMed
Summary
This summary is machine-generated.

Negative ion electrospray ionization (ESI) efficiency for acids is enhanced by charge delocalization. A model using ionization degree and WAPS predicts ionization efficiency (logIE) for phenols and benzoic acids.

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Area of Science:

  • Analytical Chemistry
  • Physical Chemistry

Background:

  • Negative ion electrospray ionization (ESI) is less studied than positive ion mode.
  • Understanding factors influencing negative ion formation is crucial for mass spectrometry applications.

Purpose of the Study:

  • To investigate the efficiency of negative ion formation in ESI for substituted phenols and benzoic acids.
  • To correlate ionization efficiency (logIE) with molecular properties.

Main Methods:

  • Electrospray ionization mass spectrometry (ESI-MS) in negative ion mode.
  • Calculation of molecular properties using COSMO-RS, including weighted average positive sigma (WAPS) and ionization degree (α).

Main Results:

  • Higher ionization efficiency was observed for acids yielding anions with highly delocalized charge (high WAPS).
  • A linear model incorporating ionization degree (α) and WAPS accurately predicted logIE for both phenols and benzoic acids (R² = 0.83).

Conclusions:

  • Ionization efficiency in negative-ion ESI is predictable using solution ionization degree and charge delocalization (WAPS).
  • The developed model demonstrates broad applicability and universality for various acidic compounds.