tmifan
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I don't really understand this....

If the stationary phase was polar and the moving phase was non- polar e.g. Hexane. Then non- polar compounds would pass through the column more quickly than polar compounds as they would have a greater solubility in the non-polar moving phase


and what it has to do with intermolecular forces?


Thanks
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Dinasaurus
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Well in this case greater polarity is likely due to a hydroxyl group or species that can form hydrogen bonds, therefore you can estimate that the longer it takes for something to pass through the more polar it is due to intermolecular forces. However in reality you wouldn't really use Chromatography on it's own, like Gas Chromatography is usually coupled with Mass Spectroscopy.
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charco
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(Original post by tmifan)
I don't really understand this....

If the stationary phase was polar and the moving phase was non- polar e.g. Hexane. Then non- polar compounds would pass through the column more quickly than polar compounds as they would have a greater solubility in the non-polar moving phase


and what it has to do with intermolecular forces?


Thanks
Things dissolve because of intermolecular (interparticular) forces.

1. There are forces of attraction between solvent particles
2. There are forces of attraction between solute particles
3. There are forces of attraction between solvent and solute particles.

If force 3 is strong enough to overcome forces 1 & 2 then the solute dissolves. This is not an all or nothing situation and there is a range of solubilities from insoluble to very soluble.

Fundamentally the process must be energetically favourable overall (this also includes entropy, but let's keep it simple)

Polar substances can make better bonds with polar solutes and so can dissolve them.

Non-polar substances can make better bonds with non-polar solutes and so can dissolve them better.

All of these principles come into play with chromatography.

A non-polar solvent will be able to carry a non-polar solute through a polar stationary phase rapidly, but a non-polar solvent will not be able to carry a polar substance through a polar stationary phase very well at all.

Clearly, there will be a range of degrees of polarity for the mobile phase, stationary phase and solute, which can be employed to separate soluble components.
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tmifan
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Report Thread starter 4 years ago
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(Original post by charco)
Things dissolve because of intermolecular (interparticular) forces.

1. There are forces of attraction between solvent particles
2. There are forces of attraction between solute particles
3. There are forces of attraction between solvent and solute particles.

If force 3 is strong enough to overcome forces 1 & 2 then the solute dissolves. This is not an all or nothing situation and there is a range of solubilities from insoluble to very soluble.

Fundamentally the process must be energetically favourable overall (this also includes entropy, but let's keep it simple)

Polar substances can make better bonds with polar solutes and so can dissolve them.

Non-polar substances can make better bonds with non-polar solutes and so can dissolve them better.

All of these principles come into play with chromatography.

A non-polar solvent will be able to carry a non-polar solute through a polar stationary phase rapidly, but a non-polar solvent will not be able to carry a polar substance through a polar stationary phase very well at all.

Clearly, there will be a range of degrees of polarity for the mobile phase, stationary phase and solute, which can be employed to separate soluble components.
Thanks! i get it now
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