Chromatography

• Chromatography

  • Used to separate mixtures if coloured compounds - simple chromatography is carried out on paper.
• Chromatography

  • Involves placing a spot of the mixture on a pencil line, drawn near the bottom of a piece of chromatography paper. Paper is then placed upright in a suitable solvent like water and as solvent soaks up the paper, it separates out the different components of the mixture.
• Chromatography -notes

  • Line must be in pencil as it’s insoluble in water and will not move as chromatography progresses.
  • Ink spot must be above level of water at start - if below, ink will run into water at bottom of beaker and not travel up the paper.
  • The more soluble the component of mixture is, the further up it travels.
• • The separated components of the mixtures of chromatography can be compared and identified by calculating the retardation factor (Rf).
• Equation:

  • Rf = distance moved by the substance (pigment) / distance moved by the solvent
• • Rf value = a measure of how soluble a particular substance is in a solvent - the larger the Rf value, the more soluble the substance is in the solvent.
• Chromatography - Rf value of two pigments