Selective sampling and in-situ detection of As(III) and As(V) in groundwater by diffusive gradients in thin-films...

The labile forms of elements have been extensively conducted due to their distinctive ecological toxicity and bioavailability. Nevertheless, the selective extraction and in-situ detection of these species from the environment pose significant challenges. In this study, two selective adsorption matrices, thiol-functionalized mesoporous silicon modified polyacrylamide gel (MCM-41-SH-PAM) and polyethyleneimine functionalized polyacrylamide gel (PEI-PAM), were developed as binding phases in diffusive gradients in thin-films technique (DGT) devices for the highly selective extraction of As(III) and As(V), respectively. The results showed that MCM-41-SH-PAM achieves 99.5 % adsorption of As(III) within 12 h with only 0.6 % cross-adsorption of As(V), while PEI-PAM adsorbs over 99.0 % of As(V) within 1 h with merely 3.8 % adsorption of As(III) even after 12 h. The adsorbed As(III) and As(V) can be eluted using 0.5 mol/L HNO₃+H₂O₂ and 0.5 mol/L HNO₃ with stable recovery rates of 80 % and 94.5 %, respectively. Combined with precise inductively coupled plasma source mass spectrometer (ICP-MS) detection of the eluent, the method achieves ultra-low detection limits of 0.04 μg/L for As(III) and 0.02 μg/L for As(V), outperforming many conventional speciation analysis techniques. Furthermore, the developed DGT devices demonstrate robust performance across a wide range of environmental conditions and maintain high accuracy in environmental samples, overcoming the limitations of existing methods that are susceptible to matrix interference.