Empore™ Chelating Disks provide a way to selectively remove multivalent metal cations from solutions.  This selectivity can be used to concentrate metals from a sample for analysis or to isolate and remove metal interferences from a complex organic or inorganic sample matrix.  In the latter case, the purified filtrate is ready for use.  The chelating disk has an affinity for multivalent (primarily 2+ and 3+) transition elements.  The functional group exhibits differing ionic charges depending on the pH of the solution.  At pH 2, the carboxylate groups are neutral and the nitrogen has a net positive charge.  This allows the sorbent to function as a weak anion exchanger.  Increasing the pH ionizes the carboxylate groups and at pH =5, both are negatively charged.  As the pH approaches neutral, the sorbent functions as a cation exchanger or a chelating resin.