Solid phase extraction of metal ions using immobilised chelating calixarene tetrahydroxamates

The synthetic macrocycles, known as calixarenes, have been shown to possess high ionophoric selectivity and form inclusion complexes with many ions. A tetrameric calixarene bearing hydroxamic acid functional groups was synthesised and supported on octadecylsilica and XAD-4 resin. When loaded with Fe(III), V(V) and Cu(II), the materials display the characteristic visible absorption spectra associated with hydroxamate coordination. The chemical bonding of the calixarene tetrahydroxamic acid to silica particles was also carried out using the triethoxysilane derivative of the p-allylcalix[4]arene hydroxamic acid. When packed into small cartridges, these materials are used for the solid phase extraction of transition metal ions from aqueous solution. Metal uptake profiles as a function of pH are presented for Fe(III), Co(II), Pb(II), Cd(II), Mn(II), Ni(II), Zn(II) and Cu(II). The quantitative trace enrichment of Cu(II), Zn(II) and Mn(II) from water samples prior to ion chromatographic analysis is demonstrated.