The mercapto-functionalized silica (MPS) diffusive gradients in thin-film (DGT) devices, for the first time, were characterized by the determination of dissolved inorganic Sb-III. The performance of MPS-DGT was assessed by (1) determining the diffusion coefficient of Sb-III in polyethersulfone membrane, (2) assessing the uptake efficiency and digestion efficiency of MPS for Sb-III, (3) investigating the effect of pH, ionic strength (as NaNO3) and foreign ions on the performance of MPS-DGT for Sb-III species, and (4) assessing the validation of MPS-DGT for the measurement of dissolved inorganic Sb-III in spiked water samples. The diffusion coefficient of Sb-III measured in the PES membrane by a diffusion cell was (3.05 +/- 0.09) x 10 (6) cm(2) s (1). There was a tendency toward higher adsorption affinity for Sb-III compared with SbV. Mass vs. time measurements of MPS-DGT at pH 6 (0.01 mol L-1 NaNO3) demonstrated a linear uptake of Sb-III (R-2 = 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 Sb-III. The presence of foreign ions (such as Ca-II, Mg-II, Cd-II, Zn-II, Cu-II, As-III and SbV) has no significant influence on the uptake of Sb-III by MPS-DGT. MPS-DGT can quantitatively measure the concentration of dissolved inorganic Sb-III in spiked etching wastewater. In spiked natural freshwater, the concentration of dissolved inorganic Sb-III obtained by MPS-DGT is significantly lower than the concentration of added Sb-III due to the presence of natural organic matter (8.7 mg C L-1) which would have complexed a fraction of the added Sb-III and thereby changed the speciation of added Sb-III. The MPS-DGT device can potentially be used as a tool for speciation measurements of Sb-III in aqueous environments.
