What are isotopes Same proton, different neutrons
Why do isotopes have similar chemical properties Same electronic structure
What are the stages of TOF spectrometry
1. Ionisation
2. Acceleration
3. Flight Tube
4. Detection
The ways of ionising the sample and when it is used?
1. Electron impact gun fired at sample knocking of valence e- forming a positive ion. Used
for elements with low formula mass because larger formula mass samples can fragment when
fired with a gun.
2. Electrospray Ionisation, sample dissolved in a volatile solvent and injected through a live
needle with a high voltage tip. The sample then gains an H+ from the needle tip, the solvent
evaporates, the sample moves toward nthe egative plate.
What is the formula used in the Acceleration stage of TOF KE= 1/2mv^2
As all particles have the same KE, the velocity of each particle depends on the mass. Lighter
particles have a faster velocity
What occurs during the flight tube stage? The smaller particles have faster velocity, will
move faster in the drift area. Ions are distinguished by different flight times.
Equation used in Flight Tube stage? t = d/v
What occurs at the detection stage of TOF? Ions reach the detector and generate a small
current
How is a small current generated during the detection stage? Electrons are transferred
from the detector to positive ions
The size of the current is proportional to the abundance of the species.
Where are Mass spectrometers used outside of the lab? Planetary space probes
How to measure Mr of Molecule when Electron impact ionisation is used? The peak with the
highest m/z value will be due to the complete molecule. There will be different peaks due to
the fragmentation caused when firing the electron gun.
How to measure Mr of Molecule when Electrospray ionisation is used? No fragmentation
will occur, so there will only be one peak equal to the mass of the MH+ ion. Minus 1 for the
H+ to find out the Mr of M.
Define first ionisation energy The enthalpy change that occurs when one mole of a gaseous
atom forms one mole of gaseous ions with a 1+ charge.
Define second ionisation energy The enthalpy change that occurs when one mole of
gaseous 1+ ions from one mole of gaseous 2+ ions.
Why do isotopes have similar chemical properties Same electronic structure
What are the stages of TOF spectrometry
1. Ionisation
2. Acceleration
3. Flight Tube
4. Detection
The ways of ionising the sample and when it is used?
1. Electron impact gun fired at sample knocking of valence e- forming a positive ion. Used
for elements with low formula mass because larger formula mass samples can fragment when
fired with a gun.
2. Electrospray Ionisation, sample dissolved in a volatile solvent and injected through a live
needle with a high voltage tip. The sample then gains an H+ from the needle tip, the solvent
evaporates, the sample moves toward nthe egative plate.
What is the formula used in the Acceleration stage of TOF KE= 1/2mv^2
As all particles have the same KE, the velocity of each particle depends on the mass. Lighter
particles have a faster velocity
What occurs during the flight tube stage? The smaller particles have faster velocity, will
move faster in the drift area. Ions are distinguished by different flight times.
Equation used in Flight Tube stage? t = d/v
What occurs at the detection stage of TOF? Ions reach the detector and generate a small
current
How is a small current generated during the detection stage? Electrons are transferred
from the detector to positive ions
The size of the current is proportional to the abundance of the species.
Where are Mass spectrometers used outside of the lab? Planetary space probes
How to measure Mr of Molecule when Electron impact ionisation is used? The peak with the
highest m/z value will be due to the complete molecule. There will be different peaks due to
the fragmentation caused when firing the electron gun.
How to measure Mr of Molecule when Electrospray ionisation is used? No fragmentation
will occur, so there will only be one peak equal to the mass of the MH+ ion. Minus 1 for the
H+ to find out the Mr of M.
Define first ionisation energy The enthalpy change that occurs when one mole of a gaseous
atom forms one mole of gaseous ions with a 1+ charge.
Define second ionisation energy The enthalpy change that occurs when one mole of
gaseous 1+ ions from one mole of gaseous 2+ ions.
