Mercury Film Microelectrodes Research Articles

Determination of metal ions extracted by DTPA in a soil treated with effluent using an Hg-electroplated-Pt microelectrode

Determinations of Cu, Fe, Mn and Zn were performed in an oxisol soil treated with effluent originated from a biodigester septic cesspool. The extracts were obtained from a DTPA/TEA (pH 7.3) solution and analysed by electroanalytical methodologies using square wave anodic stripping voltammetry (SWASV) for the analysis of Cu, Mn and Zn and square wave voltammetry (SWV) for Fe analysis, both of them with a thin mercury film microelectrode (ME-Hg). DTPA (diethylenetriaminepentaacetic acid) complexes with Cu, Mn and Fe show electroactivity in the potentials range close to the ones for the free ions in solution, but the Zn complex did not show any electroactivity at the potential range analysed. SWASV/ME-Hg and SWV/ME-Hg results were in good agreement (r2 = 0.996) with the flame atomic absorption spectroscopy (FAAS) analyses, demonstrating that electroanalytical methodologies can be used for micronutrient determinations in soil extracts without serious interferences of the matrix components. Some characteristics of the complex formed between DTPA-metals are explored by EPR experiments.

Comparison of Ion-Selective and Carbon Fiber Mercury Film Microelectrodes for Cadmium Measurement

Cadmium ion-selective microelectrodes and carbon fiber mercury film microelectrodes were fabricated and compared in this research. In order to determine whether either microelectrode could be used in biofilm microenvironmental profile studies, their performances were evaluated under different pH, buffer concentration, and ionic strength conditions. Both microelectrodes showed good linearity during calibration. pH did not have a significant impact on the ion-selective microelectrode, but significantly changed the performance of the carbon fiber mercury film microelectrode. Tris buffer was evaluated for pH control and found to increase readings of both microelectrodes. Ionic strength had a similar impact on both microelectrodes. Both microelectrodes had high selectivity for Cd 2+ , but potential interferences should be considered when real samples are to be measured.

ストリッピングボルタンメトリーを適用した鉛汚染土壌のオンサイト評価手法の開発

A method for the on-site estimation of lead contamination in soil by anodic stripping voltammetry using a mercury film microelectrode was developed. The optimized pretreatments were as follows: 1 g of soil sample was initially dried using a hot plate for 30 min with stirring; the sample was then extracted of lead with 33ml of a 1 mol·l-1 hydrochloric acid solution at 70°C for 15 min; the extract was finally filtered through a disk type glass fiber filter and a membrane filter. The lead extracted was electrodeposited on the microelectrode at -1.3V vs. Ag/AgCl for 2 min and the deposits were then stripped at a rate of 50 mV·s-1 to 0.15V vs. Ag/AgCl. By the application of a heated hydrochloric acid solution as an extracting solvent, the extraction time was greatly reduced compared with that of the official method based on soil contamination countermeasures law. The downsizing of the extraction was achieved using this method. The downsizing allowed the use of a portable mini-shaking machine and enabled the on-site extraction of lead from soil. The proposed method could be sufficiently applied to the on-site soil survey of lead contamination from bullets at a shooting range.

Ex situ preparation of bismuth film microelectrode for use in electrochemical stripping microanalysis

A study on the preparation and characterisation of ex situ formed bismuth film microelectrodes (BiFMEs) is presented, focusing in particular on their stable and reliable stripping electroanalytical performance. The potentiostatic pre-plating of the bismuth film onto a single carbon fibre substrate microelectrode was investigated and optimised with the aim of achieving long-term electrochemical and mechanical film stability. Several important film preparation parameters, such as plating agent, potential and time, and composition of the plating solution were examined with respect to the current signals of 40 consecutive adsorptive cathodic stripping voltammetry (AdCSV) measurements of trace Co(II) as model analyte. A comparison, also presented, of the stripping performance between bismuth and mercury film microelectrodes revealed a distinct practical advantage of the BiFME. The resulting optimised BiFME exhibited, besides excellent long-term film functional stability, attractive stripping analytical performance. Employing AdCSV with square-wave voltammetric detection, highly linear behaviour was obtained in the examined concentration range, with limits of detection of 70 and 90 ng/l and excellent reproducibility with 2.4 and 2.9% relative standard deviation at the 1 μg/l level ( n = 10), for Co(II) and Ni(II), respectively, achieved using only 2 min preconcentration time in the presence of dissolved oxygen. In addition, the performance of the proposed ex situ prepared BiFME in both anodic stripping voltammetry (ASV) of Cd(II) and Pb(II) and in AdCSV of Co(II) and Ni(II) from the same test solution is demonstrated. The ex situ prepared BiFME represents a promising non-toxic, environmentally friendly microsensor for detection at microlocations and in microvolumes, in particular where in situ bismuth film electrode preparation is inappropriate, inconvenient or impossible.

水銀膜微小電極を用いたストリッピングボルタンメトリーによる土壌中亜鉛，カドミウム，銅及び鉛の簡易迅速定量

A simple and rapid method was developed for the determination of zinc, cadmium, copper and lead at the mg·kg-1 level in soil samples by anodic stripping voltammetry using a mercury film microelectrode (surface area, 240μm2). Pre-electrolysis was performed at -1.3V vs. Ag/AgCl for 2min with stirring in a 0.1mol·l-1 acetic acid-sodium acetate buffer solution (pH 4.2). After the stirring was stopped, anodic stripping voltammograms for deposits were recorded in the potential range of -1.3 to 0.15V vs. Ag/AgCl at a scan rate of 50mV·s-1 in a differential pulse mode. Calibration curves (peak height vs. concentration) were linear (correlation coefficient >0.999) over the 0.2 to 10μg·l-1 concentration range with a relative standard deviation of approximately 5% for 1μg·l-1 (n=5). The detection limits (3σ) calculated from the repeated determination of 0.1μg·l-1 metal ions for a deposition time of 2min ranged from 0.04 to 0.07μg·l-1. Possible interferences were evaluated. This method was successfully applied to the simultaneous determination of zinc, cadmium, copper and lead in several soil samples without any separation steps of matrix elements. The time required for an analysis was within 3min.

Adsorptive Stripping Voltammetric Determination of Venlafaxine in Urine with a Mercury Film Microelectrode

An adsorptive stripping voltammetric procedure for the determination of the antidepressant venlafaxine in urine using a mercury film microelectrode was developed. The method is based on controlled adsorptive accumulation of the drug at the potential of −1.00 V (vs. Ag/AgCl) in the presence of 1.25 × 10−2 mol L−1 borate buffer (pH 8.7). Urine samples were analyzed directly after performing a ten-fold dilution with the supporting electrolyte but without other pretreatment. The limit of detection obtained for a 30 s collection time was 0.693 × 10−6 mol L−1. Recovery experiments gave good results at the 10−6 mol L−1 level (bias less 5% were obtained).

Application of stripping voltammetry and microelectrodes in vitro biocompatibility and in vivo toxicity tests of AISI 316L corrosion products

Adsorptive stripping voltammetric procedures, using mercury film microelectrodes, were optimised and applied to quantify total iron, chromium and nickel in samples of osteoblast-like cells culture medium and mice organs (liver, kidney and spleen) obtained from, respectively, in vitro and in vivo 316L stainless steel corrosion products biocompatibility and toxicity studies. The methods were based on the pre-concentration of the iron-catechol complex by adsorption at the potential of -1.80 V (vs. Ag/AgCl), of the chromium-diethylenetriaminepentaacetic acid complex at -1.00 V or -1.15 V (vs. Ag/AgCl) and of the nickel-dimethylglyoxime complex at -0.70 V (vs. Ag/AgCl). The detection limits achieved for each metal ion (i) in the culture medium were 1.93x10(-8) mol/L Fe, 2.80x10(-10) mol/L Cr and 7.70x10(-9) mol/L Ni for a collection time of 30 s, 40 s and 10 s, respectively, and (ii) in the mice organ solutions were 1.37x10(-8) mol/L Fe, 1.54x10(-8) mol/L Cr and 1.58x10(-9) mol/L Ni for an adsorption time of 25 s, 25 s and 15 s, respectively. The accuracy of the proposed procedures was verified by comparison of the results obtained by adsorptive stripping voltammetry with those attained by atomic absorption spectrometry for the same set of samples and good agreement was found. The in vitro study showed that stainless steel corrosion products affect the expression of the osteogenic phenotype. The in vivo mice model, used to investigate the systemic effects provoked by the corrosion products per se, indicated that Fe, Cr and Ni are partially accumulated in the organs studied and that Ni induced the more significant morphological alterations.

Application of Adsorptive Stripping Voltammetry to the Determination of Trace Levels of Titanium in Mice Organs

Trace levels of titanium (Ti) in mice organs were determined by adsorptive stripping voltammetry (AdSV) using mercury film microelectrodes (MFM). The method is based on the interfacial accumulation of Ti(IV)/mandelic acid complex by absorption at the potential of –0.15 V onto the MFM in the presence of mandelic acid 5.00×10–3 mol/L and potassium chlorate 4.00×10–2 mol/L at pH 3.4–3.5. The dependence of the peak current on different experimental variables is reported. The results achieved by AdSV were compared to those obtained by atomic absorption spectrometry (AAS) to guarantee the accuracy of the electroanalytical method developed. A significant accumulation of titanium was seen in the mice spleen, liver and the kidney under the test conditions described here. The histological studies showed that this metal was relatively well tolerated and did not induce abnormal morphological changes in the cells of the organs studied during the time of study.

Studies of Transport Phenomena and Electrostatic Interactions in Polyacrylate Gels

The transport of uncharged electroactive probes, 1,1‘-ferrocenedimethanol and 4-hydroxy-TEMPO, and electroactive cations, Tl+, was studied in polyacrylate hydrogels using steady-state voltammetry at platinum and mercury film microelectrodes. It was found that, for concentrations of polymer less than 1.5%, the diffusion coefficient of uncharged probes does not differ significantly from that observed in aqueous solutions without a polymeric network. For the probe cation, strong electrostatic interactions were observed between Tl+ and anionic polymeric networks; those interactions resulted in a significant decrease in the diffusivity of Tl+ cations. Experimental data for Tl+ transport in sodium polyacrylate gels were compared with predictions of Manning's theory for polyelectrolyte solutions. Electrostatic interactions between Tl+ and anionic polyacrylate three-dimensional gel network were found stronger than those predicted for solutions of an equivalent polyelectrolyte. Electrostatic effects for gels were ...

Chromium Determination in Osteoblast-Like Cell Culture Medium by Catalytic Cathodic Stripping Voltammetry with a Mercury Microelectrode

A catalytic cathodic stripping voltammetric procedure for the determination of total chromium in osteoblast-like cell culture medium using a mercury film microelectrode (MFM) was optimised. The method is based on the pre-concentration of the Cr(III)-diethylenetriaminepentaacetic acid (DTPA) complex by adsorption at the potential of-1.00 V (vs. Ag/AgC1) in the presence of 10 x 10(-3) mol/L DTPA, 0.70 mol/L sodium nitrate, 0.04 mol/L sodium acetate and 1.0 x 10(-3) mol/L potassium permanganate at pH 5.9-6.0. The limit of detection obtained for a 40 s collection time was 2.80 x 10(-10) mol/L of chromium. The results achieved by stripping voltammetry using the MFM were compared to those obtained by atomic absorption spectrometry (AAS) to ensure the reliability of the electrochemical method. This procedure proved to be an alternative to AAS and valuable in biocompatibility studies performed in vitro using osteoblast-like cells.

Adsorptive Stripping Measurements of Iron Accumulation in Mice Kidney Using Microelectrodes and Histological Features

The toxic effects caused by iron in kidney was performed on experimental studies with mice following administration of a metallic solution of this species to simulate the iron corrosion products of a metallic implant. To quantify the total levels of iron present in this organ, an electrochemical method was chosen based on the application of square wave voltammetry using adsorptive collection of iron-catechol on a mercury film microelectrode (MFM). The optimal working conditions to produce a very stable and reproducible iron peak in the digested kidney samples were found to be pH = 7.2 provided by 8.0 mmol/L PIPES buffer, catechol concentration of 3.0 x 10(-4) mol/L, deposition potential -1.80 V and deposition time 20 s. These results were compared with those obtained by atomic absorption spectrometry (AAS) indicating a good performance of the electrochemical method used. The analytical results show an increase of iron concentration with treatment time, which indicates that this metal ion is partially accumulated in the kidney. This accumulation induces with time some morphological alterations as evidenced by the histological analysis.

Transport of Probe Ions in Solutions of Biological Polyelectrolytes

Transport of monovalent cations was studied in solutions of biological polyelectrolytes, the sodium (or potassium) salts of anionic polysaccharides ι-, κ-, λ-carrageenan, dextran sulfate, and chondroitin sulfate, by steady-state voltammetric reduction of the probe ions Tl+ and H+ at mercury film and platinum disc microelectrodes, respectively. Diffusion coefficients of the electroactive probe ion are determined rapidly and precisely from steady-state, transport-limited current at microelectrodes in solutions with large excess and without supporting electrolyte over a wide range of polyelectrolyte and probe ion concentrations. Electrostatic interactions between polysaccharide anion and probe ion decrease the value of the diffusion coefficient of the probe ion with respect to the value without the polyelectrolyte, with the most pronounced effect in solutions without electrolyte. These interactions are quantified by the transport ratio, D/D0, of the diffusion coefficient of the probe ion with polyelectrolyte...

Square-wave anodic stripping voltammetry of Zn(II) as a method for probing instabilities at a glassy carbon mercury film microelectrode

Square-wave anodic stripping voltammetry (SWASV) has been used to characterize spontaneous changes in the voltammetric response of 50 ppb Zn(II) in 10 mM KNO 3/10 mM HNO 3 at 10 μm diameter glassy carbon mercury film microelectrode. The mercury film microelectrode was prepared by ex situ deposition of Hg(II) with the film thickness approaching the diameter of the electrode. A change from electrochemically reversible to irreversible behavior is attributed to the morphology of the mercury film on the carbon electrode. Similar changes in the Zn(II) SWASV signal can be induced at a more conventionally sized 3 mm diameter glassy carbon mercury film electrode by forced convection, but in quiescent solution the mercury film remains stable.

Indium as internal standard in square wave anodic stripping analysis of lead in blood with microelectrode arrays.

The toxic effects of lead on humans, especially children have been well documented. ASV has been an important technique in the analysis of lead in blood of humans. This research has demonstrated that indium(III) can be used as an internal standard in the analysis of lead in blood samples with mercury film microelectrode arrays. Indium is a good choice because of a low endogenous blood concentration and because baseline separation of anodic stripping peaks among Cd, In, and Pb can be achieved under appropriate conditions. The concentration of sodium bromide strongly influences the resolution of these metals and the sensitivity of ASV to In(III) in solution. Square wave anodic stripping voltammetry together with screen-printed microelectrode arrays showed that the ratio of the anodic stripping peak currents of Pb and In varies linearly with the concentration of Pb in blood samples ranging from 1.2 to 30.0 micrograms/dL. The average intraassay precision (rsd) was 6.7%.

Adsorptive stripping voltammetric measurements of chromium accumulation in mice organs using mercury film microelectrodes

AbstractChromium is the metallic species of most concern with the use of stainless steel implants. To study the distribution of chromium in mice organs with time, several animals were subcutaneously injected with 2.70 × 10−3 mol/L of chromium solution during a certain period of time. Square wave voltammetry using adsorptive collection of Cr3+ ‐DTPA complex on a mercury film microelectrode (MFM) was used for quantitation. Optimized conditions included DTPA concentration of 2.0 × 10−2 mol/L, sodium acetate 4.0 × 10−2 mol/L, sodium nitrate 0.40 mol/L, potassium permanganate 1.0 × 10−3 mol/L, pH ca. 6.1, deposition potential of −1.15 V, deposition time 20 s, frequency 100 Hz, step 2.5 mV and an amplitude of 20 mV. The detection limit of the method was 1.54 × 10−8 mol/L after deposition of 20s. Other species presented in the biological material such as calcium and iron do not interfere with the chromium determinations. The accuracy of the proposed method was checked by comparing the results with those obtained by atomic absorption spectrometry (AAS) yielding good agreement. The results showed an increase of chromium levels with time in liver, kidney and spleen, indicating that this metal is partially accumulated in the studied organs.

An approach to the calibrationless determination of copper and lead by anodic stripping voltammetry at thin mercury film microelectrodes. Application to well water and rain

A method, not demanding calibration with standard solutions of the analysed ions, is proposed for the determination of lead and copper in synthetic and real samples, by employing thin mercury film electrodes formed onto carbon disc microelectrodes. The method is based on an equation derived by exploiting the characteristics of the in situ thin mercury film formation and steady state currents achievable at microelectrodes. The conditions under which this equation is applicable are examined. In particular the effects of the nature of the electrolyte, with particular concern towards chloride ions, ionic strength and pH of the medium are investigated. The validity of the proposed method is verified on synthetic aqueous solutions. It is shown that the method can be applied to samples characterised either by a low or high ionic strength, while the solutions must be acidic (pH < 6 is recommended) and should not contain more than 1 mM of chloride ions. Real samples, as well water and rain, under conditions fulfilling the above prescriptions, are also investigated. The comparison of data obtained employing the proposed method with those taken, or evaluated by using classical calibration procedures with standard solutions, shows that agreement within 11% is found for 2 and 0.6 μg l −1 levels for lead and copper, respectively, with a relative standard deviation of about 6%. For 10 and 3 μg l −1 levels of lead and copper, respectively, which are the average values in the real samples investigated, both accuracy and RSD are around 5%.

Nickel determination in osteoblast‐like cell culture medium by adsorptive cathodic stripping voltammetry with a mercury microelectrode

AbstractThe purpose of this study is to investigate the influence of nickel, which is an alloying element in commonly used metallic biomaterials, on the biomaterials mineralization process. An electrochemical method was developed to quantify this metal ion in osteoblast‐like cell culture medium (OST) by performing adsorptive cathodic stripping voltammetry (CSV) with dimethylglyoxime (DMG) at a mercury film microelectrode (MFM). The optimized analytical conditions and the square‐wave CSV parameters for the analysis are: DMG concentration: 5.00 × 10−4 mol L−1; ammonium chloride buffer: 0.10 mol L−1 (pH 9.2); frequency: 50 Hz, amplitude 20 mV; step: 2 mV; adsorption time: 10 s, deposition potential: −0.70 V and reduction potential: −1.20 V. The limit of detection was 7.70 × 10−9 mol L−1 for an adsorption time of 10 s. The results achieved by CSV using the MFM were compared to those obtained by atomic absorption spectrometry (AAS) to ensure the reliability of the electrochemical method. The mineralization process was evaluated by biochemical and histochemical assays.

Voltammetry of Metals at Mercury Film Microelectrodes in the Absence and the Presence of Varying Concentrations of Supporting Electrolyte

The steady-state limiting current for reduction of mono and divalent metal cations to amalgam in solution without supporting electrolyte depends on both the charge of the cation and the charge of the associated anion. The ratio of limiting current in the absence of supporting electrolyte (i i o ) to diffusional current (i d ) was found to agree well with theoretical predictions (for reduction of M + , 2 and 3/2 for X - and X 2- , respectively, and for M 2+ , 3 and 2 for X - and X 2- , respectively). The reduction current of metal cation depends on the type and concentration of supporting electrolyte. The diffusional current is reached at a lower electrolyte ratio when the cation of the electrolyte is divalent than when it is monovalent in solutions without supporting electrolyte, the limiting current for reduction of a cation having a large negative reduction potential was found to increase in the presence of a cation reducing at a less negative potential. This phenomenon was observed for thallium ion with hydrogen ion and for lead ion with hydrogen ion. The increase of the current is due to the increased rate of transport of the more easily reduced cation at potentials where both reductions are transport-controlled

Analytical possibilities of microelectrode use for stripping voltammetry

The analytical utility of microelectrodes for stripping voltammetry is discussed from several points of view. The application of microelectrodes for microanalysis is demonstrated using a novel capillary flow injection system. Heavy metals at μg l−1 concentrations have been determined in μl-samples. The influence of electrode size and convection during the deposition period of anodic stripping voltammetry on the reproducibility of trace metal determination was studied for various types of electrodes. In the case of mercury film microelectrodes, the precision can be improved if the accumulation of the analyte is performed under quiescent conditions. Practical examples of stripping voltammetry with microelectrodes such as copper determination in whisky and trace metal measurements in drinking water are given.

Cyclic voltammetry involving amalgam formation at mercury film microelectrodes

AbstractCyclic voltammetry involving amalgam formation at mercury microelectrodes is described experimentally and theoretically for reversible systems. Silver microdisks were used to support the mercury deposit during the preparation of electrodes. The ratio of the mercury film thickness to the disk radius is much lower than 1 (e.g., a 1 μm thick layer of Hg on a silver disk with a radius of 15 μm) justifies the name mercury film microelectrode. When the substrate is present in the solution, the original shape of the cyclic voltammograms (one or more cathodic waves followed by one or more anodic symmetrical peaks) is the result of the combination of spherical diffusion in the solution and restricted diffusion in the mercury film. When the substrate is present initially in the mercury phase, an anodic symmetrical peak is followed by a negligibly small cathodic peak. The alternate dimension implicit and the alternate direction Galerkin methods were used in the calculations.