The Benefit of Multiple Interactions

The main benefit of having more than one type of interaction on a column is the ability to provide separation even when one separation mode has failed. For example, while a typical reverse-phase column is unable to retain polar compounds without the addition of ion-pairing reagent, Primesep® columns with their ion-exchange retention separate wide range of polar compounds without any difficulty. Primesep® columns are designed with the understanding that proper inclusion, not elimination, of secondary interaction is a powerful tool in selectivity control, column stability, and separation reproducibility. Primesep® multi-step manufacturing process guarantees good reproducibility of retention of neutral, acidic and basic compounds. The plot below shows the consistency of performance achieved on 13 lots of the stationary phases synthesized from 3 different lots of silica gel during one year.

Primesep® columns efficiently separate organic and inorganic ions in ion-exchange and ion-exclusion modes. They effectively work in normal and reverse phases, as well as in polar organic modes. Different modes of separation offer different selectivity. Working with Primesep® you won’t need an ion-pairing reagent in the mobile phase to separate ionizable polar compounds as these columns have an ion-pairing group embedded on a stationary phase. On the same column at the same time, an organic pharmaceutical can be quantified with its inorganic counter ion, or inorganic cations and anions can be run together without the ion-chromatography system. As opposed to reversed-phase columns, the selectivity of Primesep® columns can be altered not only by varying the concentration of the organic modifier, but also by changing the type and concentration of the acid modifier. These tools open a new realm of choices to alter the selectivity for the separation of various compounds previously unachievable.


Every Primesep® column has a dual chemistry stationary phase with a hydrophobic long alkyl chain and an ionizable cationic or anionic embedded group. When the polar group bears a charge, it effectively shields any other less polar groups of the stationary phase. As a result, silanol groups, which cause unwanted interaction in many reverse-phase columns, are completely undetectable and do not affect the peak shape and selectivity.