TOF mass spectrometer Flashcards
1
Q
what are the 4 stages of TOF?
A
- ionisation
- acceleration
- ion drift
- detection
2
Q
describe stage 1 (electron impact)
A
- samples are ionised to have the same charge
- in electron impact high energy electrons are shot out of an electron gun
- these electrons move one electron from each particle in the sample
- the loss of electron is what gives the PARTICLE a 1+ charge
3
Q
describe stage 2 (electrospray ionisation)
A
- the sample(s) are ionised to an equal charge/ the same charge
- the sample is dissolved in a volatile solvent like ethanol
- the sample is injected through a hypodermic needle which turns the sample into a mist
- a high voltage is applied at the tip of the needle which causes the sample to gain a H+ ion
4
Q
describe stage 3 (acceleration)
A
- the 1+ ions are attracted to the negative ELECTRIC plate which generates an electric field used to accelerate the ions
- all the PARTICLES have the same kinetic energy due to the electric field
- the velocity depends on how heavy the particle is (lighter particle = travels faster, heavier particle = travels slower)
5
Q
describe stage 4 (ion drift)
A
- the positive ions then enter the flight tube
- the particle’s WILL move at diff velocities depending on their mass (GUARANTEED) and that velocity will determine their time of flight.
6
Q
describe stage 5 (detection)
A
- the ionised sample will now collide with the negatively charged plate AT DIFFERENT TIMES (MAKE CLEAR THAT NOT EVERYONES A WINNER)
- the time in which they collide will depend on their time of flight
- the detector then gives electrons to the positively charged sample
- this causes a movement of OTHER electrons IN THE PLATE which in turn causes a current to be produced
- the current is then measured and used to calculate the number of ions colliding with the negatively charged plate and with that the abundance of molecules and with THAT can you produce a mass spectrum
