1.4 The Mass Spectrometer

Question 1

What is Mass Spectrometry?

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 is Time of Flight Mass Spectrometry?

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

What are the 5 Stages in TOF mass spectrometry?

Answer 3

Ionisation
Acceleration
Ion drift
Detection
Analysis

Question 4

What happens during Ionisaation?

Answer 4

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 (it is ionised) leaving +1 charged ions in the chamber.

Question 5

What happens during Acceleration?

Answer 5

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

Question 6

What happens during Ion drift?

Answer 6

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 7

What happens during Detection?

Answer 7

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 8

What happens during analysis?

Answer 8

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 display