Flame Emission Spectroscopy (AQA GCSE Chemistry)

Flame emission spectroscopy

• Flame emission spectroscopy is an example of an instrumental method used to analyse metal ions in solution

How does flame emission spectroscopy work?

• The sample is put into a flame 

• The light given out is passed through a spectroscope 

• The intensity and wavelength of the light emitted is measured

• The output is a line spectrum in which different elements produce lines in different parts of the spectrum

• The spectrum can be analysed to identify the metal ions in the solution and their concentrations

• Flame emission spectroscopy also works for mixtures of ions

• This is a major advantage over flame testing which can only analyse one ion at a time

A line spectrum from flame emission spectroscopy

Using reference data

• Ions in unknown samples can be identified by comparing the sample spectrum to reference spectra

• This is particularly useful if the sample contains a number of different ions

• The following flame spectrum for example was obtained for a solution containing an unknown metal:

Flame spectrum for an unknown metal 

• When compared to the reference spectra below we can see that the solution must contain sodium ions:

Diagram of a reference spectra including an emission spectrum for sodium