DESI and DART Flashcards

1
Q

Ambient Ionization

A
  • produces gas phase ions directly from the surface of the native sample with high throughput
  • requires minimal to no sample preparation
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2
Q

DESI Acronym

A
  • desorption electrospray ionization
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3
Q

DART Acronym

A
  • direct analysis in real time
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4
Q

DESI Mechanism

A
  • combination of electrospray ionization and direct ionization methods
  • sample is deposited on an insulating surface and then subjected to a beam of electrospray/charged molecules or gas-phase ions in solvent
    • spraying solution is 1:1 methanol:water which flows through a capilary at high voltage
    • spray is assisted by a nebulizing gas
  • desorbed ions are transferred to mass spectrometer through an atmospheric inlet
  • useful for residue analysis and fingerprinting
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5
Q

DESI the Good (4)

A
  • direct sampling with no preparation wich operates under ambient conditions
  • method is gentle enough for analysis of all surface types
  • effective for polar, nonpolar, biological and organic molecules
  • good for in situ analysis of biological tissues and other fragile surfaces as well as for explosives
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6
Q

DESI the Bad (3)

A
  • requires lots of optimizations to achieve quality equal to that of ESI
  • performance depends upon spray solvent, solvent flow rate, incident and collection angles, tip-to-surface distance and the nature of the surface
  • caution must be exercised with the high voltage source
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7
Q

DART Mechanism

A
  • positive mode operation where excited state helium is produced in the source
  • excited helium ionizes atmospheric water which in turn transfers protons to the sample
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8
Q

DESI vs DART (3)

A
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9
Q

DESI vs DART (5)

A
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