MASS SPECTROMETRY Flashcards
What are chlorine’s 2 isotopes and their abundances?
What is the ratio?
35Cl = 75% 37Cl= 25%
3:1 ratio
What are bromines 2 isotopes and their abundances?
What’s the ratio?
79Br = 50% 81Br = 50%
1:1 ratio
What does the size of the peak on a mass spectrum represent?
The size of the current as the size of current produced when each isotope hits the detector is used to determine the relative abundance of each isotope
What are the 2 types of ionisation used in TOF mass spectrometry and when are each used (for which type of molecules)?
Electron impact- smaller molecular compounds (with smaller masses)
Electrospray- higher Mr compounds (proteins eg)
What are the 5 stages of TOF mass spectrometry?
Victor VAPORISATION Is IONISATION A ACCELERATION Daft DEFLECTION Duck DETECTION
Which is the molecular ion on a mass spectrum?
Ion represented by highest peak furthest right
Which type of ionisation is there more likely to be fragmentation?
Electron Impact due to higher energy
Why is the sample dissolved in a VOLATILE solvent before electrospray ionisation occurs?
Volatile means the solvent has a LOW BP so sample will vapourise easily to form a gaseous sample
What happens when a 2+ charge ion is produced during ionisation?
It is affected more by magnetic field because deflection depends on charge of ion. (higher the charge, more it’s deflected) so its m/z ratio is halved
Why is the flight tube a vacuum?
So ions don’t collide with air particles (so don’t transfer energy)
What is the velocity of each particle dependent on?
ALL PARTICLES HAVE SAME KINETIC ENERGY (due to the electric field)
The mass
Lighter particles have faster velocity
Heavier particles have slower velocity
How is the mass of each particle determined?
Time of flight through the flight tube
Why are fewer 2+ ions formed in a mass spectrometer
More energy is required to knock off second electron
What is the m/z ratio
Ratio of mass to charge
