HANDOUT_CH3F2_MassSpectrometry_Barrow_Lecture 2_2023-2024 PDF

CH3F2 (Advanced Analytical Chemistry) Mass Spectrometry: Ionization Dr. Mark P. Barrow Overview Ionization methods “Mass Spectrometry: A textbook,” Jürgen Gross, Springer, ISBN: 978-3-319-54397-0 Ionization energies Electron ionization (EI) typically operated at 70 eV where 1 eV = 1.602 × 10−19 J (S...

CH3F2 (Advanced Analytical Chemistry) Mass Spectrometry: Ionization Dr. Mark P. Barrow Overview Ionization methods “Mass Spectrometry: A textbook,” Jürgen Gross, Springer, ISBN: 978-3-319-54397-0 Ionization energies Electron ionization (EI) typically operated at 70 eV where 1 eV = 1.602 × 10−19 J (See W = Q × V) “Mass Spectrometry: A textbook,” Jürgen Gross, Springer, ISBN: 978-3-319-54397-0 Electron ionization (EI) Electron energy: 70 eV Fragments EI of dodecane -C8H17 -C7H15 M+ -C6H13 -C5H11 -C4H9 -C3H7 -C2H5 https://webbook.nist.gov/cgi/cbook.cgi?ID=C112403&Mask=200 EI of peptides EI is not suitable for peptides, proteins, and other biomolecules “Soft” ionization Electrospray ionization (ESI) John Fenn Nobel prize, 2002 Matrix-assisted laser desorption/ionization (MALDI) Koichi Tanaka Nobel prize, 2002 Franz Hillenkamp Michael Karas MALDI Matrix-assisted laser desorption/ionization (MALDI) “Soft ionization” technique: no (or minimal) fragmentation Use of a laser to ablate a surface, typically on a stainless steel target Laser desorption/ionization (LDI): without the use of a matrix Matrix-assisted laser desorption/ionization (MALDI) with the use of a matrix (“softer”) Matrix-to-analyte ratio typically 1000s-to-1 Ions typically observed as protonated species or as adducts with metals: [M+H]+ [M+Na]+, [M+K]+, etc. Matrix-assisted laser desorption/ionization (MALDI) “Mass Spectrometry: A textbook,” Jürgen Gross, Springer ISBN: 978-3-319-54397-0 Matrix-assisted laser desorption/ionization (MALDI) + + + Laser “Mass Spectrometry: A textbook,” Jürgen Gross, Springer, ISBN: 978-3-319-54397-0 Most commonly, the laser uses a