MCM-41 functionalized with ethylenediaminetriacetic acid for ion-exchange chromatography

Synthesis of ED3A–MCM41 hybrid material is reported. ED3A organic moiety is an ethylenediaminetriacetic group and functionalised mesoporous silica is obtained through a “one-pot” synthesis procedure, yielding –COOH groups available on the surface without any further modification. The product has been characterized using different techniques (XRD, N2 sorption, SEM, DTG, XRF, FTIR). Due to its chemical structure, ED3A–MCM41 has been tested for on-line chromatographic application in ion exchange of probe metal ions of environmental importance (Cd2+, Cu2+ and Zn2+). In order to identify the mechanisms acting (cation-exchange and chelation) during the separation of metal ions on ED3A–MCM41, the retention behaviour with non-complexing (methanesulfonic acid) and complexing (oxalic and pyridine-2,6-dicarboxylic acids) eluents was investigated. The study revealed that the chelation mechanism is dominant in the retention of Zn2+ and Cu2+, while for Cd2+ the cation-exchange mechanism is prevailing. The different mechanisms acting on the retention of the three metal ions allowed optimizing a gradient for their separation. The chelating properties of the ED3A–MCM41 phase suggest its use for the analysis and preconcentration (and/or removal) of metal ions in highly saline matrix (synthetic sea water). Examples of separations of metal ions in this matrix are shown.