Chromatography Forum

Hellow,

I have some confusion for phenyl HPLC column. If I have compound which contain two to three phenyl ring and when i inject it on phenyl column the molecule should eluted fast due to pi-pi interaction of phenyl ring with phenyl ring of column packing. But I observed the high retention and like dissole like process is prominenet. I want to know whatt is the mechanism of phenyl column against these kind of phenyl compounds. If any one have litrature please mail me.

Regards
Praveen

Phenyl columns are first reversed-phase columns, and give retention just as other reversed-phase columns. Next they give specific retention increments for analytes that interact via pi-pi interactions, or a lack of increment for analytes that do not have such specific interactions. Also, acetonitrile itself shows some pi-pi interactions, which suppresses some of the stationary phase effects.

Journal of Chromatography A, 1127 (2006) 161–174

Phenyl ring compounds interact with the Phenyl ring part of the bonded hydrophobic moiety of the stationary phase via aromatic/pi-pi interactions predominantly. This will serve to increase the retention time of your phenylic compounds specifically- And not lower the retention. Just as seen in your case.

Phenyl ring offers a different selectivity in contrast to the traditional Carbon phase.

Hope it helps.

USP L11 - "Phenyl groups chemically bonded to porous silica
particles, 1.5 - 10um in diameter"

So, this list includes: phenyl phases with different alkyl chain linkers,
biphenyls, polar embedded linked phenyls, ect.

The propyl phenyl has retention similar to C4 + added pi-pi interaction.

Generally -

Retention of solutes is a property of the Carbon load of the column.
And, technically hydrophobic compounds tend to elute faster on phenyl as compared to a traditional C18, the factor being carbon load.

However, aromatic or fused ring compounds with phenyl chains tend to stick to phenyl columns more than C18 and hence a distinction.