Novel in situ method based on diffusive gradients in thin-films with lanthanum oxide nanoparticles for measuring As, Sb, and V and in waters.

Lanthanum oxide nanoparticles (nano-La₂O₃) was used to develop a novel binding gel within an in situ passive sampler based on diffusive gradients in thin-films technique (NL-DGT) for measuring As(V), Sb(V), and V(V). Performance characteristics of NL-DGT were independent of pH (pH: 3.1-7.9 for As, 3.1-8.5 for V, and 3.1-6.5 for Sb) and ionic strength (0.1-500 mmol L^-1 for As and V, and 0.1-200 mmol L^-1 for Sb). No obvious competition effects among As, Sb, and V with different concentration ratios were found for NL-DGT measurement. Long term storage (8-188 d) of the nano-La₂O₃ gels in 0.01 mol L^-1 NaNO₃ at 4 °C did not affect their performance. During the field deployments in Yangtze and Jiuxiang River, NL-DGT measured concentrations of As and V were similar to those measured by the grab samples, while some differences were found for Sb between DGT and grab sampling because higher pH (∼8.0) in the studied rivers caused the performance deterioration of NL-DGT. Generally, the newly developed NL-DGT is suitable for monitoring As and V in freshwater from acidic to light alkaline and Sb in acidic and neutral water.