Have been using Phenomenex Phenyl-Hexyl Luna column to separate acetaminophen/sodium benzoate/pseudoephedrine. New lots don't provide separation. Does anyone know of other manufacturers of similar mixed-mode columns?

I believe only phenyl-Hexyl column on the market is the Luna.

I have not heard of other phenyl-hexyl columns. You should be aware that lot-to-lot column reproducibility becomes poorer, the more complex the bonded phase synthesis. For this reason, I avoid mixed phase columns such as this. Most users do not realize that optimizing the mobile phase and/or temperature are able to provide equivalent or (usually) better separations for most samples, compared to simply changing the column.

The direct alternative to Phenyl Hexyl is ThermoQuest's new HyPurity Advance. More details of the product can be found at http://www.hypersil.com or by e-mailing their technical support chemist on RachelP@Hypersil.com

I've used columns and I prefer the Advance. The delivery and tech support is far superior to Phenomenex too.

Please keep in mind the phenyl-hexyl from Phenomenex uses a hexyl (6 carbon) linker between the silica surface and the phenyl ring. Other phenyl hexyls are often a phenyl propyl ligand and a hexyl ligand - two ligands bonded to the silica surface not one.