mass spectrometer Flashcards
why does the mass spectrometer has a vacuum
to prevent other particles colliding the tested particles
what is the first step of the mass spectrometer?
ionisation
what are the two types of ionization
electron impact ionization and electronspray
describe election impact ionization
used for lower molecular mass.
1) its gets vaporized
2)gets bombarded with high energy electrons from an electron gun
3) An electron gets knocked off due to the repulsion causing a 1+ ion called molecular ion
4) due to its positive charge it gets attracted to the negative plate
5)the negative plays accelerated them through to the mass spectrometer. Its can be broken. into fragments causing different peaks to show
describe electrospray ionisations
used for higher molecular mass
1) its dissolved in a volatile solvent
2) this solvent gets injected into the mass spectrometer using a hyperemic needle producing mist
3) The needle is attached to a high power voltage so when the sample is ejected it gains a proton from the solvent
4)the solvent evaporates and the H+ ion are attracted towards the negatively charged plate which accelerates them through the mass spectrometer
whats the second stage of mass spectrometer
since the ion gets attracted to the negatively charged plated it gets accelerated towards it depends on its mass as they all get accelerated at the same speed so the velocity is dependent in its mass
what is the third stage of mass spectrometer
ion drift: the ions will pass through a hole in the negatively charged plate towards the flight tube. there time of flight depends on their velocity’s at this point particles will be moving at different speeds
what is the fourth stage of mass spectrometer
once it passes through the mass spectrometer, the ion will gain an electron as it will hit a negatively charged detector plate. This discharges the ion causing a current to be produced. The size of the current is proportional to the abundance of those ions hitting the plate
