Chemical Ionization Mode
Chemical Ionization Mode - Related Videos
01:21
Chemical Ionization (CI) Mass Spectrometry
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2024
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...
03:12
Ionization Energy
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2020
The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy (IE1). The first ionization energy for an element, X, is the energy required to form a cation with 1+ charge: The energy required to remove the second most loosely bound electron is called the second ionization energy (IE2). The energy required to remove the third electron is the third ionization energy, and so on. Energy is always required...
06:21
Imaging of Biological Tissues by Desorption Electrospray Ionization Mass Spectrometry
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Cited by 21 •
2013
Desorption electrospray ionization mass spectrometry (DESI-MS) is an ambient method by which samples, including biological tissues, can be imaged with minimal sample preparation. By rastering the sample below the ionization probe, this spray-based technique provides sufficient spatial resolution to discern molecular features of interest within tissue sections.
08:54
Characterizing Bacterial Volatiles using Secondary Electrospray Ionization Mass Spectrometry (SESI-MS)
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Cited by 40 •
2011
Secondary electrospray ionization mass spectrometry (SESI-MS) enables the detection of volatile organic compounds (VOCs) without the need for any sample pretreatment. This protocol provides instructions for the rapid (within minutes) characterization of bacterial VOCs using SESI-MS.
02:37
Types of Chemical Bonds
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2020
Chemical bonding theories were pioneered by American chemist Gilbert N. Lewis. He developed a model called the Lewis model to explain the type and formation of different bonds. Chemical bonding is central to chemistry; it explains how atoms or ions bond together to form molecules. It explains why some bonds are strong and others are weak, or why one carbon bonds with two oxygens and not three; why water is H2O and not H4O. Ionic Bonds Ions are atoms or molecules bearing an electrical charge.
FAQs
The reagent gas is ionized before the analyte enters the reaction environment. Its ions then interact with analyte molecules through proton transfer, charge exchange, or adduct formation. These reactions produce detectable species such as [M+H]+, allowing the measured ion mass to provide information about the analyte’s molecular mass.
Limited fragmentation preserves more of the molecular-ion information than extensive fragmentation would. This makes the observed ion, including a protonated or adducted form, useful for estimating molecular mass and supporting compound identification. The resulting spectrum can therefore provide a complementary perspective when structural interpretation requires both mass information and fragment evidence.
These reaction pathways alter how the analyte appears in the mass spectrum. Proton transfer can generate a species such as [M+H]+, while charge exchange transfers charge between the reagent ion and analyte. Adduct formation attaches the analyte to another charged species. Recognizing these possibilities helps researchers interpret detected peaks without treating every peak as the neutral molecule itself.
First, the reagent gas is ionized to create reactive reagent ions. The analyte is then exposed to those ions, which react through proton transfer, charge exchange, or adduct formation. The resulting analyte-related ions are measured by mass spectrometry, and their masses are interpreted to support molecular-mass determination and compound characterization.
This mode is useful when researchers analyze biological compounds and want the molecular ion information to remain prominent. Supported applications include metabolites, lipids, drugs, and other biomolecules. Preserving that information can assist identification when a simpler molecular-mass signal is more informative than a spectrum dominated by extensive fragmentation.
Chemical ionization and electron ionization can contribute different evidence to compound characterization. Chemical ionization helps preserve molecular-ion information, whereas electron ionization data can provide complementary spectral information through its different ionization behavior. Comparing the two types of data can strengthen identification of metabolites, drugs, lipids, and related biological analytes.