Forensic Chemistry > 6. All elements have identifiable emission spectra and this can be used to identify trace elements > The Use of a Line Emission Spectra >
Discuss the use of line emission spectra to identify the presence of elements in chemicals
- Atomic Emission Spectroscopy is useful in analyzing the emission spectrum of a particular element, given the fact that each element has a unique emission spectrum.
- The sample is vaporized and is placed in flame or carbon arc. The flame or the voltage between the carbon arc excites the electron, which emits radiation as they fall back to the ground state. The radiation passes through a monochromator which separates the radiation into its constituent wavelength. The wavelengths are detected by photographic film, photomultiplier, or eyepiece.
- AES is more commonly used for qualitative analysis (e.g. identification of elements in a mixture) since it can analyze samples with multiple elements and distinguish between them. This is more efficient than AAS, which requires a different cathode lamp for each element
- The emission spectra can also be used for quantitative analysis. However, Atomic Absorption Spectroscopy (AAS) is much more accurate for quantitative analysis, as measuring the amount of radiation absorbed can be used to measure the concentration of the elements present
- Common uses:
- Monitoring the composition of steel to ensure its quality
- Monitoring water quality by measuring concentrations of metal ions
- Determining the lead content in soil, water or air to detect lead poisoning