Various electroanalytical methods for the determination of uranium in different matrices

A Novel Eco-Friendly and Highly Sensitive Solid Lead-Tin Microelectrode for Trace U(VI) Determination in Natural Water Samples

For the first time a solid state lead-tin microelectrode (diameter ϕ 25 µm) was utilized for U(VI) ion determination by adsorptive stripping voltammetry. The described sensor is characterized by high durability, reusability and eco-friendly features, as the need for using lead and tin ions for metal film preplating has been eliminated, and consequently, the amount of toxic waste has been limited. The advantages of the developed procedure resulted also from the utilization of a microelectrode as a working electrode, because a restricted amount of metals is needed for its construction. Moreover, field analysis is possible to perform thanks to the fact that measurements can be carried out from unmixed solutions. The analytical procedure was optimized. The proposed procedure is characterized by two orders of magnitude linear dynamic range of U(VI) determination from 1 × 10^-9 to 1 × 10^-7 mol L^-1 (120 s of accumulation). The detection limit was calculated to be 3.9 × 10^-10 mol L^-1 (accumulation time of 120 s). RSD% calculated from seven subsequent U(VI) determinations at a concentration of 2 × 10^-8 mol L^-1 was 3.5%. The correctness of the analytical procedure was confirmed by analyzing a natural certified reference material.

A novel spectrofluorimetric method based on a reaction with an azoisoxazoles-benzenesulfonamide derivative for determination of uranium (VI) ions in water samples

Selective fluorometric detection and determination of uranium ions is provided here using a novel fluorescent reagent, namely (E)-4-([4-hydroxynaphthalen-1-yl]diazenyl)-N-(5-methyleisoxazol-3-yl) benzenesulfonamide (UVI reagent). The UVI reagent offers a selective fluorescence enhancement behaviour at emission wavelength = 557 nm. The parameters affecting fluorometric detection of uranium ions, such as the pH, solvent type, ligand concentration, interaction time, and interfering ions, were investigated and adjusted. The proposed UVI reagent can detect and determine uranium ions even at low concentrations, for which the obtained limit of detection was 0.1 ppm. Additionally, this proposed determination protocol was successfully used to detect, monitor, and determine uranium ions in actual water samples.

Aggregation-induced emission active tetraphenylethene-based sensor for uranyl ion detection

A novel tetraphenylethene-based fluorescent sensor, TPE-T, was developed for the detection of uranyl ions. The selective binding of TPE-T to uranyl ions resulted in a detectable signal owing to the quenching of its aggregation-induced emission. The developed sensor could be used to visually distinguish UO2(2+) from lanthanides, transition metals, and alkali metals under UV light; the presence of other metal ions did not interfere with the detection of uranyl ions. In addition, TPE-T was successfully used for the detection of uranyl ions in river water, illustrating its potential applications in environmental systems.

Characterization of the biochemical-pathway of uranium (VI) reduction in facultative anaerobic bacteria

Cultures of U(VI) reducing bacteria sourced from abandoned uranium mine tailing dam were evaluated for their ability to reduce U(VI) to U(IV). The species in the cultures reduced U(VI) in solutions with initial U(VI) concentration up to 400mgL(-)(1) under a near neutral pH of 6.5. The electron flow pathway and fate of reduced species was also analysed in the individual species in order to evaluate the potential for control and optimisation of the reduction potential at the biochemical level. The results showed that U(VI) reduction in live cells was completely blocked by the NADH-dehydrogenase inhibitor, rotenone (C23H22O6), and thioredoxin inhibitor, cadmium chloride (CdCl2), showing that U(VI) reduction involves the electron flow through NADH-dehydrogenase, a primary electron donor to the electron transport respiratory (ETR) system. Mass balance analysis of uranium species aided by visual and electron microscopy suggest that most U(VI) reduction occurred on the cell surface of the isolated species. This finding indicates the possibility of easy uranium recovery for beneficial use through biological remediation. Should the U(VI) be reduced inside the cell, recovery would require complete disruption of the cells and therefore would be difficult. The study contributes new knowledge on the underlying mechanisms in the U(VI) reduction in facultative anaerobes.