Mass Spectrometer Flashcards
1
Q
whats the purpose of the mass spectrometer
A
- relative atomic mass of elements
- relative abundance of isotopes
- relative molecular mass of a molecule
2
Q
what are the 4 stages of mass spectrometry
A
ionisation
acceleration
ion drift
detection
3
Q
describe ionisation stage
A
the sample is ionised to give it a positive charge
4
Q
what are the types of ionisation
A
electro spray
electron impact
5
Q
describe electrospray ionisation
A
- sample dissolved in solvent
- sample pushed through small nozzle at high pressure
- voltage applied > each particle gains H+ ion
- solvent removed > leaves a gas made up of positive ions
6
Q
describe electron impact ionisation
A
- sample vaporised
- “electron gun” is used to fire high energy electrons at the gas
- this knocks one electron off each particle > forms 1+ ions
7
Q
describe acceleration
A
- positive ions are accerlated by an electric field
- electric field provides same kinetic energ to each particle
- lighter ions = greater acceleration
8
Q
describe ion drift
A
- particles enter a region with no electric field
- particles drift through it at the same speed they left the acceleration chamber
- lighter ions = higher speed
9
Q
describe detection
A
- ions reach the detector
- detector detects current created when ion hits it and records how long it took to pass through
10
Q
why do the particles in sample need to be ionised
A
because without the positive charge they wouldn’t accelerate through the electric field or be able to be detected
