TOF & THE MASS SPECTROMETER

Question 1

What does mass spectrometry do?

Answer 1

Identifies elements by determining isotopes present in a sample.

Question 2

4 steps in a mass spectrometer?

Answer 2

Ionisation (electron impact or electrospray)
Accelleration
Flight tube (ion drift)
Detection

Question 3

Optional 5th stage in a mass spectrometer?

Answer 3

analysis

Question 4

What happens in the ionisation step of TOF?

Answer 4

Sample of an element is vaporised and injected into the mass spectrometer.

this causes electrons to be removed

Only +1 charged ions are left in the chamber

Question 5

What happens in the accelleration step of TOF?

Answer 5

Positively charged ions from ionisation are accellerated to the SAME KINETIC ENERGY towards a negatively charged detection plate

Question 6

What happens in the flight tube step of TOF?

Answer 6

Heavier ions take longer to move through and lighter ions take less time.

Ions are distinguished by flight times

Question 7

What happens in detection step of TOF?

Answer 7

When the positive ions hit the negative detection plate, they gain an electron and produce a flow of charge.

The greater the abundance, the greater the charge produced

Question 8

What happens in the analysis step of TOF?

Answer 8

A mass spectrum is created using the data from the 4 previous steps

Question 9

What do you have in the TOF equation?
(5 things)

Answer 9

kinetic energy
mass
velocity
time of flight
length of flight tube

Question 10

When is electron impact used?

Answer 10

on substances with low formula mass

Question 11

When is electrospray ionisation used?

Answer 11

On larger organic molecules