In situ redox speciation analysis of chromium in water by diffusive gradients in thin films using a DE81 anion exchange membrane

A method for the in situ redox speciation analysis of chromium in water by the diffusive gradients in thin films (DGT) technique using a DE81 anion exchange membrane was successfully developed. For the selective uptake of Cr(VI), a DGT device containing an anion exchange membrane DE81 (cellulose acetate chromatographic paper) was used (DE81-DGT), while selective uptake of Cr(III) was carried out using DGT devices containing the Chelex-100 resin (Chelex-100-DGT). A correlation coefficient of 0.993 was obtained for the linearity of the immersion curves (mass versus time) using DE81-DGT. The diffusion coefficient values for Cr(VI) through the agarose diffusive layer were equal to 4.89±0.5×10−6cm2s−1 and 3.95±0.02×10−6cm2s−1 (T=23±1°C, I=0.03molL−1 NaNO3) were obtained by using diffusion cell and immersion curves, respectively. The retention of Cr(VI) by the DE81 membrane in a synthetic sample and river water was not affected by the pH over a wide range 4–9). Recoveries of Cr(VI) between 90% and 120% from solutions of ionic strength ranging from 0.01 to 0. 5molL−1 NaNO3 were achieved. Finally, the redox speciation analysis of Cr(III) and Cr(VI) in spiked river water and synthetic samples was performed with recoveries greater than 80% and 87% by using Chelex-100-DGT and DE81-DGT devices, respectively. Those results were in excellent agreement with the diphenylcarbazide spectrophotometric method. [Display omitted] •An anion exchange paper-based ligand for DGT is proposed for selective Cr(VI) uptake.•The diffusion coefficient of Cr(VI) through agarose gel is reported.•A DGT method for selectively determining Cr(VI) and Cr(III) in situ was developed.•The method was successfully applied for Cr redox speciation analysis in water.