Mercury Film Electrode Research Articles

Preconcentration of Trivalent Lanthanide Elements on a Mercury Film from Aqueous Solution Using Rotating Disk Electrode Voltammetry

An approach to concentrate trivalent lanthanide elements into or onto mercury film electrodes supported on rotating disk glassy carbon electrodes in small volumes (<or=1000 microL) is described. La(3+) was used as a model for the trivalent f-element cations because its standard potential is the most negative. La(3+) cathodically sorbed onto or into a preformed Hg film electrode from LiCl. After initial characterizations, Nd(3+), Eu(3+), Gd(3+), Ho(3+), and Lu(3+) were tested individually and in a mixture. ICPMS analyses demonstrated that these elements could be accumulated cathodically from LiCl solution and stripped anodically in 2% HNO(3), both individually and as a mixture. These cations can be electrochemically preconcentrated onto and stripped from the electrode in 5 min, a vast improvement over traditional approaches such as evaporation that require hours to days in some cases.

Highly Sensitive Voltammetric Speciation and Determination of Inorganic Arsenic in Water and Alloy Samples Using Ammonium 2‐Amino‐1‐Cyclopentene‐1‐Dithiocarboxylate

AbstractA simple, fast, reproducible (2.5% RSD at 3.0 μg/L), and sensitive method is described for quantifying As(III) (0.3 μg/L detection limit, 0.5–440 μg/L dynamic range). Anodic stripping voltammetry (ASV) is performed after accumulating arsenic at a mercury film electrode at −0.350 V vs. Ag/AgCl (saturated KCl) for 20 s in 0.2 M HCl containing 8 μM ammonium 2‐amino‐1‐cyclopentene‐1‐dithiocarboxylate (AACD), without oxygen removal. This is the first report of using AACD in ASV and in electrochemical quantification of As(III). Total arsenic is determined after sodium‐sulfite‐reduction of As(V) to As(III). Interferences are minimal. Method validation involved water and metal alloy samples.

Ultrasensitive determination of tungsten(VI) on pikomolar level in voltammetric catalytic adsorptive catechol-chlorate(V) system

The renewable mercury film electrode, applied for the determination of tungsten(VI) ultra traces using differential pulse catalytic adsorptive cathodic stripping voltammetry ( DP CAdSV) with presence of catechol as a ligand and chlorate(V) is presented. The calibration graph obtained for W(VI) is linear from 0.025 nM (4.5 ng L −1) to 130 nM (23.9 μg L −1) for a preconcentration time of 30 s, with correlation coefficient of 0.9989. For the renewable mercury electrode ( Hg( Ag) FE) with a surface area of 4.4 mm 2 the detection limit for a preconcentration time of 60 s is as low as 0.2 ng L −1. The repeatability of the method at a concentration level of the analyte as low as 0.09 μg L −1, expressed as RSD is 3.1% ( n = 5). The proposed method was successfully applied and validated by studying the certified reference material CTA-VTL-2 and simultaneously recovery of W(VI) from spiked water samples.

Insights into the simultaneous chronopotentiometric stripping measurement of indium(III), thallium(I) and zinc(II) in acidic medium at the in situ prepared antimony film carbon paste electrode

The simultaneous measurement of microgram per liter concentration levels of indium(III), thallium(I) and zinc(II) at the antimony film carbon paste electrode (SbF-CPE) is demonstrated. The antimony film was deposited in situ on a carbon paste substrate electrode and employed in chronopotentiometric stripping mode in deoxygenated solutions of 0.01 M hydrochloric acid (pH 2). The chronopotentiometric stripping performance of the SbF-CPE was studied and compared with constant current chronopotentiometric stripping and anodic stripping voltammetric operation. In comparison with its bismuth and mercury counterparts, the SbF-CPE exhibited advantageous electroanalytical performance; namely, at the bismuth film electrode, the measurement of zinc(II) was practically impossible due to hydrogen evolution, whereas the mercury film electrode exhibited a poorly developed signal for thallium(I). The SbF-CPE revealed favorable calculated LoDs (3 σ) of 1.4 μg L −1 for thallium(I) and 2.4 μg L −1 for indium(III) along with good linear response in the examined concentration range from 10 to 100 μg L −1 with correlations coefficients ( R 2) of 0.992 for thallium(I) and 0.994 for indium(III) associated with a 120 s deposition time. The chronopotentiometric stripping performance of the SbF-CPE was characterized also by satisfactory reproducibility of 1.62% for indium(III), 3.96% for thallium(I) and 2.11% for zinc(II) ( c = 40 μg L −1, n = 11).

Determination of ultra-trace Sb(III) in seawater by stripping chronopotentiometry (SCP) with a mercury film electrode in the presence of copper

This work reports the determination of ultra-trace of Sb(III) in seawater by using a stripping chronopotentiometric (SCP) method with a mercury film electrode. A sensitivity and detection limit of 360 ms L microg(-1) and 8 ng L(-1) (70 pM), respectively, were accomplished for a 15-min electrolysis time. Compared to the only two chronopotentiometric methods reported for Sb(III) determination in seawater, our method is more sensitive and does not need to use a medium exchange procedure before the stripping step. Moreover, the use of a double electrolysis potential (-450 mV and -250 mV) allows the analysis of Sb(III) independently from the Cu level in the sample. The method was successfully used to study the behaviour of dissolved Sb(III) in the Penzé estuary, NW France.

Indirect determination of sulfide ions in water samples at trace level by anodic stripping voltammetry using mercury film electrode

A simple and sensitive indirect determination method for sulfide in water samples by anodic stripping voltammetry (ASV) using mercury-film electrode (MFE) has been developed, which is based on the determination of residual cadmium ion after reaction of Cd2+ with S2−. The linear range is adjustable depending on Cd2+ concentration, for example, the determination of S2− can be achieved in the range of 1.5–7.0 × 10−6 mol L−1 by selecting 3.0 × 10−6 mol L−1 Cd2+. The detection limit is 1.3 × 10−8 mol L−1 under optimum conditions, and the relative standard deviation (RSD, n = 10) for 2.0 × 10−6 mol L−1 S2− is 0.7%. Compared with other methods, this method has the following prominent advantages: with low detection limit, easy to operate and less interference. The proposed method has been successfully applied to the determination of S2− in synthetic wastewater, lake water, beverage, spring water and real wastewater samples.

Hybrid signal processing in voltammetric determination of chromium(VI)

This study presents different hybrid signal processing algorithms which are useful in the interpretation of voltammetric signals recorded on mercury film electrodes for the determination of Cr(VI). Because of the complex character of the distortions (random, fast increasing, nonlinear, background noise and other perturbations) the application of a complex numerical procedure is necessary. In this work different variants of hybrid algorithms are utilized: adaptive degree polynomial filter, baseline generation and subtraction, signals ratio method, orthogonal signal correction and continuous wavelet transformation with dedicated mother wavelet. The operation and effectiveness of proposed procedures were tested by the determination of very low concentrations of Cr(VI) in synthetic and river water samples.

Determination of Se(IV) in natural waters by adsorptive stripping voltammetry of 5-nitropiazselenol

The high tendency of 5-nitropiazselenol for self-accumulation on thin mercury film electrode was used innovatively for determination of Se(IV) in natural waters. 5-Nitropiazselenol was formed by reaction between Se(IV) and 4-nitro-1,2-phenylenediamine in acidic solution and self-accumulation process was carried out directly from reaction media. The adsorbed 5-nitropiazselenol was stripped in HCl solution by DP cathodic potential scan. All parameters influencing the measurement were optimized and evaluated. Detection limit of this method is 0.06 ng mL −1. Interferences of various cations and anions were studied. The adsorption tendency of some other piazselenols made by some aromatic ortho-diamines was also investigated. The problems arising from applying potential during accumulation process in natural waters analysis were discussed. This method was applied for determination of Se(IV) in natural waters collected from some internationally registrated lagoons south of Caspian Sea. The obtained results were compared with the results of ICP-AES and DPCSV after electrochemical preconcentration.

Ultratrace Xanthine Determination in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

A stripping method for the determination of xanthine at the submicromolar concentration level is described. The method is based on controlled adsorptive accumulation of xanthine at a thin-film mercury electrode followed by a linear scan voltammetry measurement of the surface species. Optimum experimental conditions were found to be the use of a 5.0 × 10−3 M NaOH solution, an accumulation potential of 0.00 V, and a scan rate of 20 mV s−1. The response of xanthine is linear over the concentration range 20–140 ppb. For an accumulation time of 30 min, the detection limit was found to be 36 ppt (2.3 × 10−10 M). The more convenient relations for measuring xanthine in the presence of the metals, hypoxanthine, amino acids, and other nitrogenated bases were also investigated. The utility of the method is demonstrated by the presence of xanthine in adenosine-5′-triphosphate or DNA.

Microscopic and electrochemical characterization of lead film electrode applied in adsorptive stripping analysis

Lead film electrodes (PbFEs) deposited in situ on glassy carbon or carbon paste supports have recently found application in adsorptive stripping voltammetric determination of inorganic ions and organic substances. In this work, the PbFE, prepared in ammonia buffer solutions, was investigated using scanning electron microscopy, atomic force microscopy and various voltammetric techniques. The microscopic images of the lead films deposited on the glassy carbon substrate showed a considerable variability in microstructure and compactness of the deposited layer depending on the selected experimental conditions, such as the concentration of Pb(II) species, the nucleation and deposition potential, and the time applied. The catalytic adsorptive systems of cobalt and nickel in a solution containing 0.1 ammonia buffer, 2.5 × 10 −5 M nioxime and 0.25 M NaNO 2 were employed to investigate the electrochemical characteristics and utility of the in situ prepared lead films. The optimal parameters, i.e. the lead concentration in the solution, the procedure of film removal, and the time and potential of lead nucleation and film deposition for the adsorptive determination of metal traces, were selected, resulting in the very good reproducibility (RSD = 4.2% for 35 scans) of recorded signals. The voltammetric utility of the lead film electrode was compared to that of glassy carbon, mercury film and bismuth film electrodes, and was subsequently evaluated as superior.

Application of Anodic Stripping Voltammetry for Zinc, Copper, and Cadmium Quantification in the Aqueous Humor: Implications of Pseudoexfoliation Syndrome

Anodic stripping voltammetric (ASV) procedure, using mercury film electrode, was optimized and applied to determine the concentrations of zinc, cadmium, and copper in the aqueous humor. Concentration levels as low as 1 ppb of the test metals was possible to be detected using short electrolysis times (120 s) and microquantities of aqueous humor (up to 35 μL). As a first application of the voltammetric analysis of trace metals in the aqueous humor, the role of the three selected trace elements in the pseudoexfoliation (PEX) syndrome was examined. Samples from aqueous humor were collected during cataract extraction from patients with and without PEX. The zinc and copper concentration levels in the aqueous humor did not show statistically significant difference in the study and control group. Cadmium was detected in a small number of samples, without however statistical differences between the two groups. ASV proved to be a highly precise and sensitive tool for the quantification of heavy metal ions in aqueous humor. Further studies may lead to useful conclusions for the role of zinc, copper, or cadmium in PEX syndrome.

An Experimental Investigation of Quasireversible Maximum of Azobenzene on Mercury Electrode by Fourier Transformed Square‐Wave Voltammetry

AbstractAn experimental investigation of quasireversible maximum (QRM) of azobenzene on mercury electrode by two methods, i.e., traditional square‐wave voltammetry (SWV) and fast Fourier transformed square‐wave voltammetry (FT‐SWV), was presented, and the influence factors on QRM of FT‐SWV were discussed. The results show that the rate constants derived from FT‐SWV agree with that of derived from traditional SWV with acceptable differences, showing a sound verification that the rate constants derived from FT‐SWV were reliable. In addition, some theoretical predictions on FT‐SWV were experimentally confirmed through the characterization of strongly adsorbed azobenzene on mercury film electrode. As a result, FT‐SWV is further proved to be a powerful technique in kinetic studies of the surface adsorbed processes.

Determination of selenium in natural waters by adsorptive differential pulse cathodic stripping voltammetry

In this work bovine albumin was used innovatively as a medium for adsorptive accumulation of Se–I 2 on thin mercury film electrode. Se–I 2 was formed by reaction between Se(IV) and iodide in HCl media. The adsorbed Se–I 2 was stripped in 0.05 M HCl by differential pulse cathodic potential scan. The proposed method was successfully applied to analysis of Se(IV) and Se(VI) in natural waters sampled from some lagoons south of Caspian Sea. The optimum reaction conditions and other analytical parameters and influence of cations and anions were studied. The detection limit was 0.37 ng mL −1. The obtained results were compared with the results of DPCSV after electrochemical preconcentration, HG-AAS and ICP-AES.

Fast procedure for no-reference inversion-voltammetric determination of lead in aqueous solutions

Possibility of no-reference inversion-voltammetric determination of lead in aqueous solutions with the use of a preliminarily determined coulometric constant of the electrochemical cell, which enables substantially faster analysis as compared with the known analogs, was studied. The coulometric constants of electrochemical cells with a mercury film electrode were found for different solution volumes.

Evaluation of poly(sodium 4-styrenesulfonate) film coating in thin mercury film electrodes for lead determination

In this work, polyelectrolyte coatings assembled on glassy carbon/thin mercury film electrodes, as an adsorbed layer of poly(sodium 4-styrenesulfonate) (PSS), were studied. The goal was to search for the best conditions for the production of stable PSS-coated electrodes that could present high negative charge densities within the thin polymeric film, providing a fast and significant electrostatic cation accumulation. Square-wave anodic stripping voltammetry was applied to measure the amount of incorporated lead used as the reference cation. The influence of the composition of the PSS solution, the amount of deposited PSS, molecular weight and of the ionic strength of the electrolyte solution, on the features of the PSS coatings for ion-exchange voltammetry was studied. The PSS films morphology was assessed by SEM. The best PSS coating performance was found for the electrodes prepared from water solutions with a molecular weight of at least 70,000, and a mass loading of ca. 8 μg mm −2. In these conditions a three fold increase was observed in low ionic strength (0.0032 M) media. However, this improvement was not sufficient for the application of direct ion-exchange voltammetry, thus different strategies to obtain polymer films with higher charge densities have to be envisaged.

Electrochemical behavior of valsartan and its determination in capsules

Electrochemical behavior of valsartan has been carried out in Britton–Robinson (B–R) buffer solution at pH 7.0 at the mercury film electrode (MFE) by cyclic, linear sweep, differential-pulse and square-wave voltammetry. The property of valsartan adsorption at the MFE using accumulation potential of +0.10 V was observed. The effects of experimental parameters on electrochemical process at the MFE were discussed. Differential-pulse adsorptive stripping and square-wave adsorptive stripping voltammetry for the valsartan determination were proposed, linearity was found in the range of 6.0 × 10 −8 to 4.0 × 10 −6 mol/L. The detection limits were 2.93 × 10 −9 and 3.27 × 10 −9 mol/L, respectively. The proposed methods were also applied to the commercial valsartan with good recoveries.

Application of a renewable silver based mercury film electrode to the determination of Cr(VI) in soil samples

The design and experimental results of the application of a renewable mercury film silver based electrode to the determination of Cr(VI) in soil samples are presented. The main feature of this procedure is that it can be used in field measurements. The procedure is based on the extraction of total Cr(VI) exploiting the complexation property of diethylenetriaminepentaacetic acid (DTPA) followed by electrochemical reduction of Cr(VI) to Cr(III) with the formation of Cr(III)-H2DTPA complex adsorbed on mercury film electrode. The voltammetric signal is caused by reduction of this complex. The validation of the proposed procedure was made by Cr(VI) determination in the certified reference material “Chromium VI in soil”. The protocol for Cr(VI) determination has also been applied to the analysis of Rendoll soil samples with satisfying precision.

Square-wave anodic-stripping voltammetric determination of Cd, Pb, and Cu in a hydrofluoric acid solution of siliceous spicules of marine sponges (from the Ligurian Sea, Italy, and the Ross Sea, Antarctica)

Square-wave anodic-stripping voltammetry (SWASV) was set up and optimized for simultaneous determination of cadmium, lead, and copper in siliceous spicules of marine sponges, directly in the hydrofluoric acid solution (approximately 0.55 mol L(-1) HF, pH approximately 1.9). A thin mercury-film electrode (TMFE) plated on to an HF-resistant epoxy-impregnated graphite rotating-disc support was used. The optimum experimental conditions, evaluated also in terms of the signal-to-noise ratio, were as follows: deposition potential -1100 mV vs. Ag/AgCl, KCl 3 mol L(-1), deposition time 3-10 min, electrode rotation 3000 rpm, SW scan from -1100 mV to +100 mV, SW pulse amplitude 25 mV, frequency 100 Hz, DeltaE(step) 8 mV, t(step) 100 ms, t(wait) 60 ms, t(delay) 2 ms, t(meas) 3 ms. Under these conditions the metal peak potentials were Cd -654 +/- 1 mV, Pb -458 +/- 1 mV, Cu -198 +/- 1 mV. The electrochemical behaviour was reversible for Pb, quasi-reversible for Cd, and kinetically controlled (possibly following chemical reaction) for Cu. The linearity of the response with concentration was verified up to approximately 4 microg L(-1) for Cd and Pb and approximately 20 microg L(-1) for Cu. The detection limits were 5.8 ng L(-1), 3.6 ng L(-1), and 4.3 ng L(-1) for Cd, Pb, and Cu, respectively, with t(d) = 5 min. The method was applied for determination of the metals in spicules of two specimens of marine sponges (Demosponges) from the Portofino natural reserve (Ligurian Sea, Italy, Petrosia ficiformis) and Terra Nova Bay (Ross Sea, Antarctica, Sphaerotylus antarcticus). The metal contents varied from tens of ng g(-1) to approximately 1 microg g(-1), depending on the metal considered and with significant differences between the two sponge species.

The convection-driven non-additivity of the faradaic currents for the parallel reduction of some metal and hydrogen cations at the mercury electrode

An atypical example of the effect of the self-induced convection on the morphology of current-potential responses was described, for the case of the parallel electroreduction of some metal cations (Cd 2+, Cu 2+, Zn 2+ and Eu 3+) and H + ions at the mercury electrode. Separation of the individual faradaic contributions from the metal ions and hydrogen ions reduction, made with the double potential-step chronocoulometry, and based on the difference between the rates of these processes, allowed us to find that the total faradaic current exhibits negative or positive deviations from the sum of individual faradaic currents. In order to diagnose the origin of this anomaly, the series of experiments for various acid concentrations, electrolysis times and the electrode types/geometries, including the hanging mercury drop and the mercury film electrodes, were performed. The results obtained indicated that the observed anomalies are due not to the surface blocking or latent limiting currents, but due to a rather novel mechanism that involves convective instabilities which accompany the hydrogen evolution reaction. The resulting change of the concentration distribution of all species involved in the electrode process appropriately changes the individual contributions from the faradaic currents. These studies show one more role of convection in electrochemical systems.

Electrochemical Stripping Techniques in Analysis of Nucleic Acids and their Constituents

The ability of nucleic acids (NA) and their components to accumulate at electrode surfaces and electrochemical properties of these species are closely related. This review is devoted to electrochemical stripping techniques applied in NA studies. Cathodic or anodic stripping voltammetry have been used for a highly sensitive determination of nucleobases, nucleosides, nucleotides or acid-hydrolyzed NAs, based on formation of sparingly soluble complexes of the NA constituents with electrochemically generated mercury or copper(I) ions. DNAs, RNAs and their synthetic analogues, either unmodified or labeled with electroactive markers, have been analyzed by adsorptive stripping (AdS) techniques with mercury, mercury film, amalgam and carbon-based electrodes. Strong adsorption of NAs at the electrode surfaces has been utilized in adsorptive transfer stripping (AdTS) techniques. In AdTS, a NA-modified electrode is prepared by adsorptive accumulation of the NA at the electrode surface, followed by transfer into background electrolyte not containing any NA. NA-modified electrodes can be used as simple electrochemical NA sensors. Recent applications of AdS and AdTS in NA microanalysis, in detection of DNA damage as well as in studies of DNA hybridization or DNA-protein interactions are reviewed.