Complex Interaction

Unique elution order of positively charged molecules in a chelating HPLC system

SIELC Technologies has developed a new class of columns with combined reverse-phase, cation exchange, and complex-formation properties in interaction with amines, sulfonium, phosphonium and metal ions. This column has a unique unparalleled selectivity for complex mixtures separation. The pH working range for these columns is from 1 to 7, but their complex formation and cation-exchange properties are substantially suppressed at the pH below 3. In order to facilitate the complex formation, the pH of the mobile phase should remain in the range of 3-7. The degree of complex formation can be adjusted by selecting the pH of the mobile phase.

The unique complex properties of the column can be observed in the separation of alkali metals ions. The ions elute on the Primesep C column in reverse order compared to ion-exchange elution. The unusual elution order is found in primary, secondary, and tertiary amines. Secondary and tertiary amines have higher pKa values than primary amines, which makes them retain longer by ion-exchange mechanism.

With the complex forming properties of Primesep C columns, the primary amines are more retainable than secondary and tertiary amines. This extraordinary elution pattern allows tailoring the separation of amines to provide the most appropriate peak order for quantitation and preparative chromatography.