Electrochemical Determination of Low Levels of Uranyl by a Vibrating Gold Microelectrode

Abstract

In this work we report the sensitive electroanalytical detection of uranium(VI) in aqueous solutions. Uranium commonly exists in aqueous solutions in the form of its oxo ion, uranyl (U(VI)O2(2+)). The detection of uranyl has been accomplished by us through its deposition upon reduction by two electrons to the insoluble UO2 using a bare disk gold macroelectrode and anodic stripping voltammetry (ASV). This gave an unsatisfactory detection limit of ca. 1 × 10(-5) M uranyl. Moreover, the evolution of hydrogen bubbles blocked the electrode surface as a result of water reduction at negative deposition potential (-0.7 V vs Ag/AgCl). The application of a 25 μm diameter Au microwire electrode on which UO2 precipitated at negative potential (-1.2 V) improved substantially the detection limit. Further improvement was accomplished by vibrating the microwire working electrode, which increased the amounts of UO2 deposition due to decreasing the diffusion layer. The effect of the vibrating amplitude and frequency on the electroanalytical response was studied and optimized. Eventually, a detection limit of ca. 1 × 10(-9) M uranyl was achieved using a 5 min deposition time, -1.2 V deposition potential, and vibrating the electrode at frequency of 250 Hz and amplitude of 6 V.

Electroanalysis in environmental monitoring: Tracking trace metals—A mini review

“…Mandler [40] used a simple loudspeaker connected to the waveform generator. Recently, a gold plated Ir based microelectrode (Au IrM) for determination of As(III) at low nM level and at natural pH was presented by Touilloux et al [41].…”

Design and synthesis of target-responsive hydrogel for portable visual quantitative detection of uranium with a microfluidic distance-based readout device

“…Lu group reported the discovery of a DNAzyme for detection of uranyl (UO 2 2+ ) with ultrahigh sensitivity and selectivity based on the cleavage of substrate strand by enzyme strand upon recognition of UO 2 2+ (Liu et al 2007). The sensor was applied in the fluorescent (He and Lu 2011;Wu et al 2013;Zhang et al 2015b) and electrochemical detection (Ma et al 2014;Peled et al 2015) of UO 2 2+ after modification with fluorescent and electrochemical tags, respectively. Colorimetric methods were also developed with gold nanoparticles (AuNPs) (Lee et al 2008).…”

Bis[2-(methacryloyloxy)ethyl] phosphate radiografted into track-etched PVDF for uranium (VI) determination by means of cathodic stripping voltammetry

“…Another important choice was an electrolyte and pH as both parameters affect on redox mechanism of uranyl. Peled et al report that 50 mM acetate buffer (pH3) with 100 mM KNO 3 is the best medium for the detection of low concentration of uranyl in water [22].…”

“…There are not many reports about electrochemical detection of uranium. Peled et al report the determination of uranyl using gold microelectrodes by anodic stripping voltammetry [22]. Another technique among the few is to use a gold electrode chemically modified by POCl 3 capable quantifying µM uranyl concentrations [23].…”