Non polar stationary Phase and Non polar Compounds

[samar12]

How can I explain interaction between Non-polar stationary phase like C18 bonded silica with non-polar compounds? Which forces are involved here? will non-polar compounds adsorb on the non-polar stationary phase?

[tom jupille]

You would be surprised how far the schoolboy chemistry class rule will carry you: "like dissolves like and like sticks to like".

Actually, reversed-phase retention is arguably driven primarily by hydrophobicity: the water molecules in the mobile phase are pulled together by their hydrogen bonds and squeeze the analyte molecules onto (or into) the stationary phase. An alternative model suggests that hydrophobicity tends to push organic modifier onto the surface of the stationary phase and analyte molecules partition between the water-rich mobile phase and the organic-rich surface layer.

Both of those descriptions are gross oversimplifications. If you really want to get into it, I would suggest getting a copy of the late Uwe Neue's book "HPLC Columns: Theory, Technology, and Practice". Here's a link to it on Amazon: http://tinyurl.com/7m7uc8w