Selectivty of Neutral Compounds in Mixed Mode Separations

[Victor]

Rob,

I wasn't referring to adding ion pair reagents. I presume you get little retention of the base when working at low pH which is where most people work.

Why not try neutral pH, or even slightly alkaline pH with a high pH stable column, using MS friendly buffers? You may still get enough MS sensitivity in the positive ion mode to do this. It could increase the retention of the base to higher than that of the neutrals.

[Einar Ponten]

When we do courses on chromatography our main message to the participants is to divide the chromatographic problem into three categories:

efficiancy, capacity, and selectivity

The latter is the most complicated and interesting. Maybe you should try a ZIC®-HILIC column, and in what category would it contribute?