Time of Flight Mass Spectrometry

?
  • Created by: Delta_
  • Created on: 07-12-16 16:33
What can it be used for?
finding the mass and abundance of each isotope in an element, allowing us to determine its relative atomic mass
1 of 18
Summarise what happens in TOF mass spectrometry.
particles of the substance are ionised to form 1+ ions which are accelerated so that they all have the same kinetic energy. The time taken to travel a fixed distance is then used to find the mass of each ion in the sample.
2 of 18
What happens in electron impact?
The sample being analysed is vaporised and then high energy electrons are fired at it. This knocks off one electron from each particle, forming a 1+ ion. The 1+ ions are attracted to a negatively charged plate where they are accelarated
3 of 18
What is the equation for when one electron is removed?
X(g) + e– --> X + (g) + 2e–
4 of 18
What state are the particles in?
gaseous
5 of 18
what is the +1 ion that is formed known as?
Molecular Ion
6 of 18
What happens in electrospray ionisation?
The sample is dissolved in a volatile solvent and injected through a fine hypodermic capillary needle to give a fine mist. The samples are ionised by gaining a proton from the sample as they leave the needle. The solvent evaporates.
7 of 18
Give 2 examples of volatile solvents
water and methanol
8 of 18
What is the tip of the fine hypodermic capillary needle attached to?
The positive terminal of a high-voltage power supply.
9 of 18
What is electrospray ionisation used for
higher molecular mass substances including many biological molecules such as protein.
10 of 18
What happens in acceleration?
The positive ions are accelerated using a magnetic field so they all have the same kinetic energy. The velocity of the particles therefore depends on the mass.
11 of 18
What particles have a faster velocity?
lighter particles
12 of 18
What can be used as a proton in electrospray ionisation? Why?
H+ ion: Same mass and charge as a proton
13 of 18
What happens in the flight tube?
The positive ions travel through a hole in the negatively charged plate, into a flight tube. The time of flight depends on the particle's velocity.
14 of 18
What happens in detection?
The ions hit a negatively charged plate, and are discharged by gaining an electron. the movement of electrons causes a electric current which is measured.
15 of 18
What does the computer create from the data?
A mass spectrum, showing the abundance of isotopes.
16 of 18
How do you work out the relative atomic mass?
(relative abundance x mass) / 100
17 of 18
In electron impact why may there be peaks at lower m/z values?
fragmentation of molecular ions
18 of 18

Other cards in this set

Card 2

Front

Summarise what happens in TOF mass spectrometry.

Back

particles of the substance are ionised to form 1+ ions which are accelerated so that they all have the same kinetic energy. The time taken to travel a fixed distance is then used to find the mass of each ion in the sample.

Card 3

Front

What happens in electron impact?

Back

Preview of the front of card 3

Card 4

Front

What is the equation for when one electron is removed?

Back

Preview of the front of card 4

Card 5

Front

What state are the particles in?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Mass Spectrometry resources »