Enhanced DGT capability for measurements of multiple types of analytes using synergistic effects among different binding agents.

There is a requirement for simultaneous measurements of diverse analytes to reveal their biogeochemical couplings in the environment. In this study, we first realized simultaneous measurements of three types of analytes, including sulfide [S(-II)], metallic cations, and oxyanions by diffusive gradients in thin films (DGT) using a new mixed ZrO-CA binding gel. The ZrO-CA gel exhibited faster absorption rates for oxyanions than previously reported ZrO-Chelex gel, and faster absorption rates for cations when the gel was saturated with S(-II). It implies that there were synergistic effects among the three binding agents which should facilitate the DGT uptake. The technique's performance was validated under laboratory conditions in mixtures of dissolved compounds. It was shown to be independent of the solution's pH (5-9) and ionic strength (from 1 to 3 mM to 750 mM). The capacities of the ZrO-CA DGTs without or with [S(-II)] saturation to measure As(III), As(V), Cd(II), Fe(II), and P(V) individually were significantly greater than those of other DGTs except for Zr-oxide based DGTs. The measurements in sediment revealed similar distributions of three types of analytes in the vertical profile and confirmed the feasibility and advantage of the ZrO-CA DGT. This study provides a new perspective to enhance the DGT capability in measurement of multiple analytes through utilizing the synergistic effects among different binding agents.