Chromatography Forum

For reverse phase chromatography, why are c18 columns used so much? Am curious why 18 carbons is the ideal number and and not say 20, 30, 40 etc.

Tradition.

My advisor and I discussed this. He thinks it might have just been what was handy in the lab when the first researchers added the alkyl chain to silica. Or that the C18 was just cheaper.

Here's a link on the history of reverse phase columns; it doesn't fully answer the question, but it gives a foothold:
https://www.elementlabsolutions.com/uk/ ... c18-column

My guess is that when people decided to stick a lipid onto something, they were bound to end up with C16 or C18 chains because palmitic and stearic acids are just so, so common in natural sources of fat. If you're looking for a reliable naturally-available alkane chain, that's what you'll get.

I don't know if this is just an urban legend among chromatographers - I've heard it from different people, doesn't mean it's the truth, though.
The story goes, that when the first researchers were looking for silanes to functionalize their silica, they indeed found that the C18-silane was readily available in large quantities and was rather cheap. And this was because the Coca-Cola-Company used that silane to coat their Coke-bottles, to provide some breaking portection and a matte finish to the glass surface.