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  Section: Practical Skills in Chemistry » Instrumental techniques
 
 
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Atomic spectroscopy

 
     
 
Content
Instrumental techniques
  Basic spectroscopy
    Introduction to spectroscopy
    UV Ivisible spectrophotometry
    Fluorescence
    Fluorescence spectrophotometry
    Phosphorescence and luminescence
    Atomic spectroscopy
  Atomic spectroscopy
    Atomic Absorption Spectroscopy
    Atomic Emission Spectroscopy
    Inductively coupled plasma
    Decomposition techniques for solid inorganic samples
  Infrared spectroscopy
  Nuclear magnetic resonance spectrometry
    1H-NMR spectra
    13C-NMR spectra
  Mass spectrometry
    Interfacing mass spectrometry
  Chromatography ~ introduction
    The chromatogram
    Resolution
    Detectors
  Gas and liquid chromatography
    Gas chromatography
    Liquid chromatography
    High-performance liquid chromatography
    Interpreting chromatograms
    Optimizing chromatographic separations
    Quantitative analysis
  Electrophoresis
    The supporting medium
    Capillary electrophoresis
    Capillary zone electrophoresis (CZE)
    Micellar electrokinetic chromatography (MEKC)
  Electroanalytical techniques
    Potentiometry and ion-selective electrodes
    Voltammetric methods
    Oxygen electrodes
    Coulometric methods
    Cyclic voltammetry
  Radioactive isotopes and their uses
    Radioactive decay
    Measuring radioactivity
    Chemical applications for radioactive isotopes
    Working practices when using radioactive isotopes
  Thermal analysis
    Thermogravimetry
    Applications

Atoms of certain metals will absorb and emit radiation of specific wavelengths when heated in a flame, in direct proportion to the number of atoms present. Atomic spectrophotometric techniques measure the absorption or emission of particular wavelengths of UV and visible light, to identify and quantify such metals.

Flame atomic emission spectrophotometry (or flame photometry)
The principal components of a flame photometer are shown in Fig. 26.5. A liquid sample is converted into an aerosol in a nebulizer (atomizer) before being introduced into the flame, where a small proportion (typically less than I in 10000) of the atoms will be raised to a higher energy level, releasing this energy as light of a specific wavelength, which is passed through a filter to a photocell detector. Flame photometry can be used to measure the alkali metal ions K+, Na+ and Ca2+ in, for example, biological fluids and water samples (Box 26.2).
 
Components of a flame photometer
Fig. 26.5 Components of a flame photometer.

Atomic absorption spectroscopy
This technique is applicable to a broad range of metal ions, including those of Pb, Cu, Zn, etc. It relies on the absorption of light of a specific wavelength by atoms dispersed in a flame. The appropriate wavelength is provided by a hollow cathode lamp, coated with the element to be analysed, focused through the flame and onto the detector. When the sample is introduced into the flame, it will decrease the light detected in direct proportion to the amount of metal present. Practical advantages over flame photometry include:
  • improved sensitivity;
  • increased precision;
  • decreased interference.
The technique can be used with or without a flame. In the flameless technique several variations are possible, including a graphite furnace or cold vapour, all of which are more sensitive than flame photometry.


 
     
 
 
     



     
 
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