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
2
Q
DESI Acronym
A
- desorption electrospray ionization
3
Q
DART Acronym
A
- direct analysis in real time
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
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/383/962/a_image_thumb.png?1508954391)
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
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
7
Q
DART Mechanism
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/384/363/q_image_thumb.png?1508954979)
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
8
Q
DESI vs DART (3)
A
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/384/598/a_image_thumb.png?1508955121)
9
Q
DESI vs DART (5)
A
![](https://s3.amazonaws.com/brainscape-prod/system/cm/223/384/755/a_image_thumb.png?1508955176)