Sampling of dissolved inorganic SbIII by mercapto-functionalized silica-based diffusive gradients in thin-film technique
Abstract
The mercapto-functionalized silica (MPS) diffusive gradients in thin-film (DGT) devices, for the first time, were characterized by the determination of dissolved inorganic SbIII. The performance of MPS–DGT was assessed by (1) determining the diffusion coefficient of SbIII in polyethersulfone membrane, (2) assessing the uptake efficiency and digestion efficiency of MPS for SbIII, (3) investigating the effect of pH, ionic strength (as NaNO3) and foreign ions on the performance of MPS–DGT for SbIII species, and (4) assessing the validation of MPS–DGT for the measurement of dissolved inorganic SbIII in spiked water samples. The diffusion coefficient of SbIII measured in the PES membrane by a diffusion cell was (3.05 ± 0.09) × 10−6 cm2 s−1. There was a tendency toward higher adsorption affinity for SbIII compared with SbV. Mass vs. time measurements of MPS–DGT at pH 6 (0.01 mol L−1 NaNO3) demonstrated a linear uptake of SbIII (R2 = 0.9973). The performance of MPS–DGT was independent of ionic strength (0.001–0.7 mol L−1 NaNO3 at pH 5) and pH (3–8, 0.01 mol L−1 NaNO3) for the measurement of SbIII. The presence of foreign ions (such as CaII, MgII, CdII, ZnII, CuII, AsIII and SbV) has no significant influence on the uptake of SbIII by MPS–DGT. MPS–DGT can quantitatively measure the concentration of dissolved inorganic SbIII in spiked etching wastewater. In spiked natural freshwater, the concentration of dissolved inorganic SbIII obtained by MPS–DGT is significantly lower than the concentration of added SbIII due to the presence of natural organic matter (8.7 mg C L−1) which would have complexed a fraction of the added SbIII and thereby changed the speciation of added SbIII. The MPS–DGT device can potentially be used as a tool for speciation measurements of SbIII in aqueous environments.