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Spectroscopy Techniques Tutorial

Key Concepts

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Comparison of Spectroscopy Techniques used to Determine Presence and/or Amount of Substance

Type: Flame Tests
Features Uses
  • inexpensive
  • fast, but some colours may be masked by others making it unreliable
  • qualitative technique
  • limited application as many common metals (e.g., Al & Mg) do not colour a flame
  • a type of emission spectroscopy which can be observed by the naked eye or by using a spectroscope to see a series of bright lines
Identification of metals in some salts

  • Li+       crimson
  • Na+     yellow
  • K+       lilac
  • Ca2+   brick red
  • Sr2+   scarlet
  • Ba2+   green
  • Cu2+   green-blue

Type: Colorimetry
Features Uses
  • relatively inexpensive
  • fast, requiring a set of standard solutions
  • qualitative & quantitative
  • a type of absorption spectroscopy limited to coloured solutions or compounds
  • copper(II) sulfate in garden sprays
  • iron(III) concentration using KSCN to form the coloured Fe(CNS)2+ complex
  • coloured solutions such as food colourings
wavelength of light is selected for maximum absorbance & a calibration curve is constructed of absorbance versus concentration

Type: Atomic Absorption Spectroscopy (AAS)
Features Uses
  • expensive
  • fast, requiring a set of standard solutions
  • quantitative
  • a type of absorption spectroscopy that can be used for all metals and metalloids (semi-metals)
  • mercury in shellfish
  • lead in soil samples
  • trace metals in mineral waters
correct hollow cathode tube selected & a calibration curve constructed of absorbance versus concentration. (solutions may have to be diluted)

Type: UV-Visible Spectroscopy
Features Uses
  • expensive
  • fast, requiring a set of standard solutions
  • qualitative & quantitative
  • a type of absorption spectroscopy limited to coloured solutions or compounds
  • concentration of some coloured pharmaceuticals in blood serum

  • concentration of metal ions using coloured complexes

  • concentration of food colourings
wavelength of light selected for maximum absorbance and a calibration curve constructed of absorbance versus concentration

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