Unit 2 - Learning aim C: Chromatography
Use of chromatography and different types - ANSWER - Chromatography is useful
because it enables the separation, isolation, purification, and identification of
components of extremely complex mixtures
- There are different chromatography techniques:
- Paper chromatography
- Column chromatography
- Thin layer chromatography
- The results of chromatographic analysis are called chromatograms
- The number of spots or peaks correspond to the number of components in the
sample
- If only one spot appears, then the substance being tested is pure
- Identification can be carried out in planar chromatography by matching colour or
distance of an unknown sample with reference compounds
Paper chromatography - ANSWER - If a mixture is dropped onto a piece of blotting
paper, the components spread out
- The degree of spreading depends on how well the components stick to the solvent
molecules present in the piece of paper
- Th components which have the least solubility in the solvent are those which tend
to stick to the paper and so do not spread out as much as those which are. more
soluble in the solvent (so they tend not to stick and therefore spread further up the
paper)
Adsorption chromatography - ANSWER - Adsorption chromatography involves the
use of a stationary phase and a mobile phase to separate the components of a
mixture
- Adsorption is the attachment of molecules to the surface of a solid, and it occurs
when secondary bonds form between molecules and atoms at the surface of the
solid
- The compound most like the mobile phase in polarity will move the furthest along
the stationary phase
Stationary phase - ANSWER - The material onto which the components of the
mixture adsorb
- Usually a silicate and can be either non-polar, polar, or even ionic
Mobile phase - ANSWER - The liquid (or gas) that moves across the stationary
phase, carrying the mixture to be separated
- It is the solvent and is either a gas, a liquid, or a gel
Rate of movement - ANSWER - The rate of movement of each component is
dependent on the amount of secondary bonding between the components and the
stationary or mobile phase
- The compound most like the mobile phase in polarity will move the furthest and/or
the fastest along the stationary phase
Use of chromatography and different types - ANSWER - Chromatography is useful
because it enables the separation, isolation, purification, and identification of
components of extremely complex mixtures
- There are different chromatography techniques:
- Paper chromatography
- Column chromatography
- Thin layer chromatography
- The results of chromatographic analysis are called chromatograms
- The number of spots or peaks correspond to the number of components in the
sample
- If only one spot appears, then the substance being tested is pure
- Identification can be carried out in planar chromatography by matching colour or
distance of an unknown sample with reference compounds
Paper chromatography - ANSWER - If a mixture is dropped onto a piece of blotting
paper, the components spread out
- The degree of spreading depends on how well the components stick to the solvent
molecules present in the piece of paper
- Th components which have the least solubility in the solvent are those which tend
to stick to the paper and so do not spread out as much as those which are. more
soluble in the solvent (so they tend not to stick and therefore spread further up the
paper)
Adsorption chromatography - ANSWER - Adsorption chromatography involves the
use of a stationary phase and a mobile phase to separate the components of a
mixture
- Adsorption is the attachment of molecules to the surface of a solid, and it occurs
when secondary bonds form between molecules and atoms at the surface of the
solid
- The compound most like the mobile phase in polarity will move the furthest along
the stationary phase
Stationary phase - ANSWER - The material onto which the components of the
mixture adsorb
- Usually a silicate and can be either non-polar, polar, or even ionic
Mobile phase - ANSWER - The liquid (or gas) that moves across the stationary
phase, carrying the mixture to be separated
- It is the solvent and is either a gas, a liquid, or a gel
Rate of movement - ANSWER - The rate of movement of each component is
dependent on the amount of secondary bonding between the components and the
stationary or mobile phase
- The compound most like the mobile phase in polarity will move the furthest and/or
the fastest along the stationary phase
