Mass spectrometry

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Mass spectrometry
Detection of ionic species to determine the
molecular weight of and obtain structural
information on a molecule
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Mass spectrometry
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• ions only detected
• individual molecules are detected
• uses isotopic masses not MW

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Base peak Parent ion
-CH3
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-CH3
-CH3
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Isotope effects
Molecular weight Br 79.9040
Br isotopic abundance 79Br 50.5 81Br 49.5
CH379Br
CH381Br
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MS Ionization Techniques

1. Electron Impact (EI)uses beam of electrons
2. Fast Atom Bombardment (FAB)uses beam of atoms
3. Chemical Ionization (CI)uses chemical reactions
4. Matrix Assisted Laser Desorption (MALDI)uses
   lasers to ionize molecules
5. Electrosprayuses compounds which are already
   ionic