ABSTRACT
For uranyl extraction, a distinctive chelating ligand, namely ethyl 2-amino-6-hydroxy-5-(4-methoxyphenyldiazenyl)-4-phenyl-4H-benzo[f]chromene-3-carboxylate, has been synthesized and characterized using FT-IR, NMR, and ESI-MS. Subsequently, a cloud point extraction (CPE) protocol has been developed for the selective separation of the trace amounts of uranyl ions from some lanthanide ions after being captured by the ligand in the presence of non-ionic surfactant (Triton X-114). The extraction procedure has been optimized based on the concentration of the complexing agent and the non-ionic surfactant, phase separation temperatures, pH, and ionic strength. The developed CPE procedure exhibited a relatively low detection limit of 0.5 ng mL-1 in the linear range from 3 ng mL-1 to 250 ng mL-1. Furthermore, interference studies have been carried out to study the selectivity of our protocol. These studies revealed that the recoveries of uranyl ions were in the range from 96.1% to 99.9% in the presence of some lanthanide ions such as Th4+, Gd3+, and Sm3+. It is worth mentioning that the geometry optimization, reactivity, and molecular electrostatic potential maps of the ligand and the proposed UO2 2+ complex were acquired via DFT calculations to study their stabilities based on the geometry and binding affinity. The theoretical data confirmed the octahedral geometry of the UO2 2+ complex with the lowest energy and excellent stability. The robustness of the proposed methodology was evaluated by the detection of uranyl ions in different environmental samples and synthetic mixtures.
ABSTRACT
New selective and sensitive electrochemical sensors were designed based on the deposition of a promising ion imprinted polymer (IIP) on the surface of glassy carbon electrode (GCE) for the detection and monitoring of Cd(ii) in different real samples. Herein, a highly selective Cd-imprinted polymer was successfully synthesized using a novel heterocyclic compound based on the benzo[f]chromene scaffold that acted as a complexing agent and a functional monomer in the presence of azobisisobutyronitrile (initiator) and ethylene glycol dimethacrylate (cross-linker). The characterization of the synthesized chelating agent and IIP was performed using FT-IR, SEM, 1H-NMR, EIMS, and EDX analyses. After that, the voltammetric sensor was manufactured by introducing graphene oxide (GO) on the surface of GCE; then, the IIP was grown by a drop coating technique. The electrochemical characterization of the voltammetric sensor (IIP/GO@GCE) was performed by CV and EIS. For comparison, the potentiometric sensor was also prepared by embedding IIP in plasticized polyvinyl chloride and depositing it as one layer on the GCE surface. Anodic stripping voltammetry was used to construct the calibration graph; the IIP/GO@GCE exhibited a wider detection range (4.2 × 10-12-5.6 × 10-3 mol L-1) and extremely low detection limit (7 × 10-14 mol L-1) for Cd(ii). Meanwhile, the potentiometric sensor showed a linear calibration curve for Cd(ii) over a concentration range from 7.3 × 10-8 mol L-1 to 2.4 × 10-3 mol L-1 with a detection limit of 6.3 × 10-10 mol L-1. Furthermore, both sensors offered outstanding selectivity for Cd(ii) over a wide assortment of other common ions, high reproducibility, and excellent stability.
