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#ionization techniques

3 public questions tagged with this topic.

Mass Spectroscopy

Which is a soft ionization technique?

Ionization techniques are categorized as hard or soft based on extent of fragmentation induced. Hard ionization like electron ionization deposits abundant internal energy causing extensive bond cleavage. Soft methods preserve molecular ions. MALDI uses matrix buffer absorbing laser energy, producing intact singly charged ions. Fast atom bombardment bombards analyte in glycerol matrix with high-energy argon atoms, also yielding protonated molecules with little fragmentation, enabling analysis of polar peptides. Electrospray is also soft. Therefore, both MALDI and FAB qualify as soft ionization techniques, while electron ionization does not meet this gentle energy deposition criteria.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Mass Spectroscopy

What does TOF stand for in MALDI-TOF?

MALDI-TOF combines matrix-assisted laser desorption ionization with time-of-flight analyzer for rapid, sensitive mass analysis of biomolecules. TOF specifically represents time of flight, describing physical principle separating ions after desorption. After laser pulse, ions acquire nearly equal kinetic energy and travel through a field-free drift tube. Velocity inversely relates to square root of m/z, so lighter ions reach detector earlier than heavier ions. Precise measurement of flight time yields accurate m/z determination. This terminology distinguishes this analyzer from quadrupole or Orbitrap systems and explains its wide mass range for proteins and polymers.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Mass Spectroscopy

Which ionization technique uses a matrix and laser?

Matrix-assisted laser desorption ionization mixes analyte with an excess of organic matrix such as alpha-cyano-4-hydroxycinnamic acid that strongly absorbs ultraviolet laser light. A pulsed nitrogen laser at 337 nm irradiates the dried co-crystal, causing matrix excitation, rapid sublimation, and proton transfer to analyte molecules without extensive fragmentation. Electrospray ionization uses high-voltage liquid spray, electron ionization uses energetic electron beam, and fast atom bombardment uses atom beam. Only MALDI relies on photo-absorbing matrix together with laser desorption for gentle vaporization and ionization of large proteins and peptides.

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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