Comparison of some newly synthesized chemically modified Amberlite XAD-4 resins for the preconcentration and determination of trace elements by flow injection inductively coupled plasma-mass spectrometry (ICP-MS)

Abstract

XAD copolymer resins may be functionalized with heavy metal ion-selective ligands either by covalent linkage to the polymer backbone or by impregnation. These resins may be tailored to be specific for certain heavy metals by adjusting the retention and elution parameters. For the synthesis of immobilized Amberlite XAD-4 copolymer resins that are expected to preconcentrate a number of transition and heavy metals, the Schiff base method was chosen. For this purpose the copolymer was nitrated, reduced to the corresponding amine and converted to the imine compounds via a Schiff base reaction using different organic aldehyde compounds. The interactions of 8 elements (Cd, Co, Cu, Mn, Ni, Pb, U and Zn) with the resins were qualitatively investigated. Optimal pH for retention was typically 6–8 for most resins although one could be used at pH 5 and elution was achieved using 0.1 M HNO₃. The resins were characterized by FTIR, SEM and elemental analysis. It was demonstrated that the resins could be used to preconcentrate ultra-trace analytes from natural waters, and analysis of environmental certified reference materials using FI-ICP-MS showed good agreement with the certified values. Metal retention capacities were also calculated using a batch system and were found to compare favorably with other resins reported in the literature.