Simultaneous Measurements of Eight Oxyanions Using High-Capacity Diffusive Gradients in Thin Films (Zr-Oxide DGT) with a High-Efficiency Elution Procedure.

Abstract

A zirconium oxide binding gel-based diffusive gradients in thin films (Zr-oxide DGT) was developed for simultaneous measurements of P(V), As(V), Cr(VI), Mo(VI), Sb(V), Se(VI), V(V), and W(VI). All of the oxyanions were rapidly bound to Zr-oxide gel with differences in binding affinity. The eight bound oxyanions were successfully recovered by one-step elution using a mild reagent of 0.2 M NaOH-0.5 M H2O2 by overcoming the problems in analyses of the oxyanions. The optimized elution time was reduced to 3-5 h from 24-48 h required by other DGTs. DGT uptakes of all the oxyanions were independent of pH (4.42-8.45) and ionic strength (0.1-500 mM). The DGT capacities for six oxyanions detected in multioxyanion solution were only 0.19 to 0.35 times of those detected in single-oxyanion solution, reflecting a strong competition among the oxyanions during DGT uptake. Except for Se(VI) in seawater, Zr-oxide DGT accurately measured all of the oxyanions in synthetic freshwater and seawater, with the capacities ∼29 to >2397 times and ∼7.5 to 232 times those of two commonly used DGTs (Metsorb and precipitated ferrihydrite (PF) DGTs) in freshwater and seawater, respectively. Measurements by Zr-oxide DGT in contaminated sediments were in agreement with only two oxyanions with the two commonly used DGTs; the two DGTs accumulated less or no mass of other oxyanions. This study demonstrates significant advantage of Zr-oxide DGT over the other DGTs in simultaneous measurements of the eight oxyanions due to the former's high capacity and a wide tolerance to environmental interferences, together with a high efficiency in elution.