Chromatography Forum

Hi All

I know that some embeded polar stationary phases, such as the RP-Amide from Supelco and I think the Bonus RP from Zorbax, are synthesized in such a way that leaves residual amine sites on the stationary phase surface (from the incomplete reaction of the amino silane with the next reagent in the process).

Are there any polar embeded phases which are made by first creating the polar embeded group and then bonding it to the silicone surface?

Cliff

Hi Cliff,

There are. One of them is “Synergi Fusion-RP Polar embeddedâ€

All packings with an embedded polar group from Waters are created in a one-step process (the silane is synthesized first and then connected to the surface).

Columns with this feature: SymmetryShield RP18 and SymmetryShield RP8, XTerra RP18, XBridge Shield RP18, Acquity UPLC BEH Shield RP18.

All columns contain a carbamate function as the polar group, with the oxygen oriented towards the silicon Si-(CH2)3-O-CO-NH-R. The carbamate function performs very similar to the amide function, which is not true for the simple ether in other products.

Two polar-embedded stationary phases are offered by Dionex.

One is Acclaim PolarAdvantage (PA), which is sulfonamide-embedded.

The other is Acclaim PA2, an amide-embedded version.

Both packings are prepared via one-step synthesis, similar to what Uwe described.

Generally speaking, the polarity of the packings depends on the polarity of the embedded group. From my personal experience, the polarity order of different stationary phases are roughly in the following order:

C18 < sulfonamide-embedded (Dionex Acclaim PA) < carbamate-embedded (Waters Symmetry Shield RP18) < amide-embedded (Dionex Acclaim PA2, Supelco Discovery RP-Amide, ...) < Zorbax Bonus RP - high polarity due to residual unfunctionalized amines

Hopefully we can find a column from above collection with right selectivity.

Ascentis RP-Amide is a one step process. No residual amines. The first polar embedded columns on the market, sich as Suplex and Supelcosil ABZ, were two step processes.

Embedded amides and carbamates provide the best in terms of alternate selectivity and shielding of silanols while embedded ethers don't provide this improvement.

Thanks Wayne. I had the suspicion that this is the case, but had not yet seen a solid confirmation of this.