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Chromatography
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- 1Chromatographybased on separation of sample components.
- 2Types of chromatography used in food analysisQualitative - Paper, Thin Layer
Quantitative- Gas, Liquid - 3Principles of seperationLike all sep methods, chromatography depends on some physical characteristics of compounds.
It is easy to separate compounds with significant differences in physical properties.
However, many compounds are very similar, so small differences must be exploited to achieve a separation. - 4Molecular properties which separations of compounds can be based on(1) Polarity - giving physical properties of volatility, adsorption and solubility.
(2) Ionic- giving physical property of charge.
(3) Size - (mass) giving physical properties of diffusion and sedimentation.
(4) Shape- leading to ligand binding. - 5Genereal InfoMost techniques based on polarity - gas and liquid.
Ion exchange c is based on separation by charge difference.
Size exclusion - based on separation by size of molecules.
Affinity chromo - based on ability of ligand binding to the molecule. - 6Ligand Binding Assays(LBA) is an assay, or an analytic procedure, whose procedure or method relies on the binding of ligand molecules to receptors, antibodies or other macromolecules.
- 7PolarityAs many of the most useful forms of chromatography are dependant on differences between the polarity of compounds, it is important to understand what in a molecule gives rise to polarity,
- 8Polarity 2Both the solubility in a particular solvent and the volatility will be affected/ influenced by polarity.
Polarity in a molecule means that each "end" of the molecule has a slight charge associated with it.
Termed permanent dipole.
Tend to get dipole-dipole interactions, basis of adsorption chromatography. - 9WaterAs oxygen is more electronegative, slight negative charge on the O, as a result of lone pairs, water molecules tend to associate to form a H bonded lattice structure.
Other molecules showing polarity, will fit more easily into the lattice structure, stabilised by the ionic interactions. - 10ChromatographyAll separations involve the distribution of the compounds of a mixture between two seperate phases.
The distribution can be affected by solubillity, volatility, ion exchange, or affinity binding. - 11PhasesStationary phase/ Immobile - components that associate with this phase will be more "held up"
Mobile phase - this phase passes over the stationary phase, components that associate with this phase more will move more rapidly with the mobile phase. - 12—
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- Fichas sobre Chromatography, creado por aisling-hefferna el 26/11/2015.
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- aisling-hefferna
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