Cation Exchange

SIELC Technologies provides several different columns with negatively charged functional groups due to the embedded anionic ion-paring reagent. Primesep A is the strongest acidic column, while Primesep C is the weakest acidic column. The Primesep 100 and Primesep 200 columns are in between. Difference in the functional group acidity allows selecting the most appropriate column for a particular set of basic compounds that differ in their pKa value.
The embedded acidic functional group can be in an ionized form, or in a non-ionized form, depending on the pH of the mobile phase. In order to get retention by ion-exchange mechanism on Primesep® columns, the pH of the mobile phase should be selected close to, or above, the transition value of embedded acidic groups. Below the transition pH value, the column behaves as a regular reverse-phase column with an embedded non-ionized polar group.

The column name corresponds to pH value of the mobile phase where acid residue on the column switches from ionize form to neutral one.

Cation-exchange Column Type About 50% of embedded acidic groups ionized at transition pH value Separates basic compounds
Primesep 500 pH = 5.0 strong bases, dibases, polybases
Primesep C pH = 3.5 strong bases, dibases
Primesep 200 pH = 2 strong bases, dibases
Primesep P pH = 1 weak, medium aromatic bases
Primesep 100 pH = 1 weak, medium bases, AA, metals
Primesep A Ionized in all working pH weak bases, AA, metals

 

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