Novel cation-exchange column for the separation of hydrophobic and/or polyvalent amines

The term amines encompasses a wide variety of compounds: monovalent or polyvalent amines, hydrophobic or hydrophilic amines, and combinations of all of these. Due to their charge, polyvalent amines such as the biogenic amines have very strong cation-exchange interaction with the cation-exchange groups in the stationary phase. Very high acid concentrations are required to elute them effectively from a high-capacity, carboxylated cation-exchange column. The eluent must contain a divalent ion to elute them from a sulfonated cation-exchange column due to its selectivity. Chromatography for these amines with a new "tailored" amine column of moderate capacity using a simple acidic eluent is described. The hydrophobic nature of other amines, such as long-carbon-chained amines, results in partitioning into the polymeric substrate of previous carboxylated stationary phases, so that organic solvent is required to elute them effectively. The substrate resin of this new "tailored" amine column is first coated so that, when it is functionalized in a subsequent step, this type of interaction is minimized. Examples are given. Methods that require eluent gradients and/or step changes of eluent concentration are especially well suited to this column because the background conductivity remains almost unchanged under gradient conditions.