Steady-state DGT fluxes of nanoparticulate metal complexes

For a fully labile complex system, the diffusive gradients in thin film (DGT) metal flux approaches the fairly simple limit defined by the joint diffusion of the free metal ion and the complex species in the gel layer. Natural soft nanoparticulate complexes, such as those with humics and fulvics, generally enter the DGT gel phase and some of them may even be adsorbed by the gel matrix. The time characteristics of the DGT response are affected by a lower rate of diffusion, as well as by possible accumulation of nanoparticulate species in the gel layer. Several cases are discussed in some detail on the basis of numerical analysis of the diffusion process. If the difference between the diffusion coefficients of the free metal ion and the nanoparticulate complex is sufficiently large, the time-resolved DGT flux allows for distinction between these two types of species.