Development of cerium oxide-based diffusive gradients in thin films technique for in-situ measurement of dissolved inorganic arsenic in waters.

A diffusive gradients in thin films (DGT) method using a new high-capacity cerium oxide (CeO2 ) binding gel, for the first time, was developed for measuring dissolved inorganic arsenic in freshwater and seawater. The capacities of the new CeO2 binding gel were 682 μg and 375 μg for AsIII and AsV , respectively. The masses of AsIII and AsV accumulated by CeO2 -DGT device increased linearly with time and agreed well with the theoretical value calculated by DGT equation. The arsenic accumulation by CeO2 -DGT was independent of pH (4.05-9.04) and ionic strength (0.1-750 mM), and common anions including CO3 2- , SO4 2- , Cl- and PO4 3- had no obvious interference. CeO2 -DGT showed excellent long-term deployment performance in freshwater and synthetic seawater. Field trials with CeO2 -DGT achieved successfully the time-weighted-average concentrations of total inorganic arsenic in reservoir water (1.38 ± 0.09 μg/L) and coastal seawater (0.45 ± 0.06 μg/L). The results were comparable to those measured by grab sampling. The proposed method was reliable and robust for in-situ measurements of dissolved inorganic arsenic in environmental waters.