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Introduction
Ionization Techniques
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______________________ Finnigan LTQ Hardware Manual _______________________
The PhotoMate light source uses a krypton lamp which emits photons with
energies of 10.0 and 10.6 eV. Molecules with ionization potentials less than
10 eV ionize to form MH
+
while those with greater ionization potentials do
not. Figure 1-7 shows ionization potentials of typical compounds and
solvents.
Figure 1-7. Ionization potentials of typical compounds and solvents
Nanospray Ionization
Nanospray ionization (NSI)) is a technique for performing electrospray
ionization on amounts of liquid as small as 1
µ
L for time periods of greater
than 30 min. Stable mass spectra can be obtained for very small amounts of
biomolecules such as proteins, peptides, oligonucleotides, and
oligosaccharides.
For more information on NSI, refer to the manual that came with the NSI
source.
Krypton 10.0 eV, 10.6 eV
Ionization Potentials (IP)
Anthracene
7.4 eV
Fluoranthene
7.8 eV
Caffeine
8.0 eV
4-Nitrotoluene
9.5 eV
Solvent Ionization Potentials (IP)
Toluene
8.82 eV
Acetone
9.70 eV
Methanol
10.85 eV
Acetonitrile
12.19 eV
Water
12.61 eV
10. eV