Mass Spectrometry

Question 1

What does mass spectrometry do

Answer 1

This is an analytical technique used to identify different isotopes and find the overall relative atomic mass of an element.

Question 2

What does a time of flight spectrometer do

Answer 2

This form of mass spectrometry records the time it takes for ions of each isotope to reach a detector. Using this, spectra can be produced showing each isotope present.

Question 3

Ioniseation

Answer 3

lonisation - A sample of an element is vapourised and injected into the mass spectrometer where a high voltage is passed over the chamber. This causes electrons to be removed from the atoms leaving +1 charged ions in the chamber.

Question 4

Acceleration

Answer 4

Acceleration - These positively charged ions are then accelerated towards a negatively charged detection plate.

Question 5

Ion drift

Answer 5

lon Drift - The ions are then deflected by a magnetic field into a curved path. The radius of their path is dependent on the charge and mass of the ion.

Question 6

Detection

Answer 6

Detection - When the positive ions hit the negatively charged detection plate, they gain an electron producing a flow of charge. The greater the abundance, the greater the current produced.

Question 7

Analysis

Answer 7

Analysis - These current values are then used in combination with the flight times to produce a spectra print-out with the relative abundance of each isotope displayed.

Question 8

What can happen during ionisation that shouldn’t

Answer 8

During the ionisation process, a 2+ charged ion may be produced. This means it will be affected more by the magnetic field producing a curved path of smaller radius. As a result, its mass to charge ratio (m/z) is halved and this can be seen on spectra as a trace at half the expected m/z value.