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  Section: Practical Skills in Chemistry » Instrumental techniques
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Instrumental techniques
  Basic spectroscopy
    Introduction to spectroscopy
    UV Ivisible spectrophotometry
    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
  Gas and liquid chromatography
    Gas chromatography
    Liquid chromatography
    High-performance liquid chromatography
    Interpreting chromatograms
    Optimizing chromatographic separations
    Quantitative analysis
    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

It is often important to be able to separate a large number of compounds. A visual inspection of the chromatogram (Fig. 31.8) will usually indicate whether the separation is appropriate. It is desirable that the valley between adjoining peaks returns to the base line and resolution is a quantitative measure of the separation. The influence of k', α and N on resolution, R, is shown in the following expression:

⇒ Equation [31.6] R = √N × k' × α − 1  
4 k' + 1 α

Three conditions must be satisfied in order to achieve some degree of resolution:
  1. Peaks have to be retained on the column (k' > 0).
  2. Peaks have to be separated from each other (α > 1).
  3. The column must develop some minimum value of N.

A multicomponent chromatogram. Separation of many compounds, some well resolved, e.g. peaks at 12-13 mins, and others that are not, e.g. peaks at 24-25 mins
Fig. 31.8 A multicomponent chromatogram. Separation of many compounds, some well resolved, e.g. peaks at 12-13 mins, and others that are not, e.g. peaks at 24-25 mins.
Fig.31.9 Influence of k', α and N on


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