Characterization of Resin Gels for Diffusive Gradient in Thin Films Technique
AbstraktThe diffusive gradient in the film technique (DGT) is a new approach to the in-situ determinations of labile metal species in aquatic systems. The DGT device accumulates labile species from solution and therefore contamination problems associated with conventional collection and filtration procedures are eliminated. The technique employs a hydrogel layer to control the diffusive transport of metals to a cation-exchange resin, which is selective for free or weakly complexed metal ion species. This study deals with the use of a new resin based on the Spheron-Oxin®?ion exchanger in the DGT technique. The resin with a selectivity for trace metal species higher than Chelex 100 could provide more information on metal speciation in aquatic systems. Its performance was tested for Cd, Cu, Ni and Pb under laboratory conditions. The new resin provides reliable results in the pH range 6??–8, independently of ionic strength (25 mmol l−1??– 0.6 mol l−1) and also in the presence of Mg(NO3)2 (10 μmol l−1 ??– 0.05 mol l??−1). The effect of iminodiacetic acid, as a model competitive ligand on the metal uptake measured by DGT probe was also assessed.