Reverse-phase chromatography

[Marian]

First of all hello everyone

I was very surprised to find out there is actually a chromatography forum, so this is great news.
My question is, in Reverse Phase Chromatography for a mixture of benzene and para-xylene which peak is the first? It is the most polar that comes out first of course but I can't exactly find out which of those 2 it is. The dipole moment for both of them is zero.

thanks in advance

[tom jupille]

Instead of the words "polar" and "non-polar", use the approximate equivalents "hydrophilic" and "hydrophobic" (since those have Greek roots).

In reversed-phase, hydrophilic (polar) molecules elute early and hydrophobic (non-polar) molecules elute later.

Comparing your molecules, would the addition of two methyl groups to benzene make the molecule more hydrophobic or more hydrophilic?

[Marian]

Since I posted this I did some research
Turns out p-xylene is the most hydrophobic of the two
The solvent is MeOH/water 65/35 so I guess the benzene would be the fastest while the xylene would be slower in order to avoid the water...hmm

[tom jupille]

Very good!!