Science Buddies: "Ask an Expert"

Hey there, I was wondering if someone here could help me with understanding the intermolecular forces, polarity and interactions in relation to high performance liquid chromatography. Thank you.
This is in relation to my science fair project in which under close investigation I am studying the effects of the three types of chromatography and there application in a clinical context.

moderator note: I combined your two posts so the experts could see all of the informantion in a single place.

Hi monpetite69,

In HPLC, like all chromatography techniques, a mobile phase moves through or across a stationary phase. Your mobile phase will generally be a mixture of a few compounds or chemical species. As the mobile phase moves across the stationary phase, the different compounds travel at different speeds. Chemicals more attracted to the stationary phase move more slowly, compounds that don't interact much with the stationary phase move more quickly.

Several factors, including the size of the molecules, can affect how fast a given compound moves through the chromatography column. You are correct to focus on "intermolecular forces, polarity and interactions" as this is typically how we really want to separate species.

The mechanism of separation can visualized simply by thinking of oil and water. Assuming that oil (nonpolar) and water (polar) don't mix, imagine the two liquids flowing through a 'polar' pipe. The water will be somewhat attracted to the polar walls of the pipe. The 'polar' pipe is like your chromatography column. Many are lined with fully hydroxylated silica. Basically, the surface of the inside of the little tube is covered with hydroxl groups, making it very polar.

This summary looks promising: https://en.wikipedia.org/wiki/Chromatography

But I would also suggest reading a little about intermolecular forces. [hydrogen bonding, dipole-dipole interactions, Van der Waals forces, London dispersion forces, are a few keywords to try.]

I hope some of this will be of help,

-John K