Performance Characteristics of Diffusive Gradients in Thin Films Equipped with a Binding Gel Layer Containing Precipitated Ferrihydrite for Measuring Arsenic(V), Selenium(VI), Vanadium(V), and Antimony(V)

摘要

Measurements at high spatial resolution by DGT (diffusivengradients in thin films) require a binding agent that isnhomogeneously distributed in the binding layer. Formationnof ferrihydrite by in situ precipitation within a hydrogelnhas been previously shown to meet these requirementsnfor the measurement of oxyanions by DGT. Here, wenreport for the first time detailed performance characteristicsnof the binding gel and associated DGT devicesnobtained by deployment in known solutions. To allowncomparison of measured and theoretical accumulation ofnAs(V), Se(VI), V(V), and Sb(V), their diffusion coefficientsnwere determined using an independent diffusion cell.nTheoretical responses were obtained irrespective of ionicnstrength (1-100 mmol L-1) and pH (3-8), except fornSe above pH 7.8 and V below pH 5. Calculatedndetection limits, based on deployment times of 1 day,nwere lower than those for devices made with a bindingngel cast with a ferrihydrite slurry, and the measuredncapacity of the binding layer was also superior. Therenwas no evidence for interference from other oxyanions,nbut binding performance showed some deteriorationnafter 38 days of storage. The potential capability fornmeasuring labile forms of these oxyanions in acidic tonneutral, fresh to brackish waters was demonstrated.