Amalgam Electrode Research Articles

Voltammetric determination of genotoxic 4‐nitroindane at a mercury meniscus modified silver solid amalgam electrode

AbstractA silver solid amalgam electrode modified with mercury meniscus (m‐AgSAE) was used as a non‐toxic replacement of mercury electrodes in the voltammetric determination of genotoxic environmental pollutant 4‐nitroindane (4‐NI). The m‐AgSAE was used to characterize of the overall electrode process during the 4‐NI conversion using cyclic voltammetry (CV), and it was shown that the electrochemical reduction of 4‐NI is an irreversible process controlled by both diffusion and adsorption. Techniques of direct current voltammetry (DCV) and differential pulse voltammetry (DPV) at the m‐AgSAE were optimized for the development of a method for the sensitive determination of 4‐NI. The application of the more convenient DPV method was proven on authentic drinking and river water samples. Limits of quantification (LQs) obtained under the following optimal conditions were 0.1 μmol L−1 for DCV at the m‐AgSAE (Britton‐Robinson (BR) buffer pH 5.0–methanol (1 : 1); regeneration potentials E1,reg=−200 mV, E2,reg=−1100 mV) and 0.1 μmol L−1 for DPV at the m‐AgSAE (BR buffer pH 9.0–methanol (1 : 1); regeneration potentials E1,reg=−300 mV, E2,reg=−1300 mV). An attempt to decrease the LQ of the 4‐NI determination by differential pulse adsorptive stripping voltammetry at the m‐AgSAE was not successful. The LQs for DPV at the m‐AgSAE in authentic samples of drinking and river water were 1.0 μmol L−1 and 2.0 μmol L−1 (BR buffer pH 9.0–drinking or river water (1 : 9); regeneration potentials E1,reg=−300 mV, E2,reg=−1300 mV), respectively.

The use of amalgam electrodes for monitoring of organic compounds: overview of papers published from 2011 to 2023

The use of amalgam electrodes for monitoring of organic compounds: overview of papers published from 2011 to 2023

New Approaches in Electroanalytical Determination of Triazines-Based Pesticides in Natural Waters

This study describes the preparation and use of a dental amalgam electrode for the voltammetric determination of triazine-based pesticides ametryn, atrazine, and simazine in natural waters, using square wave voltammetry. The experimental and voltammetric parameters were previously optimized, and analytical curves were constructed to calculate analytical parameters. The detection limits presented values that were lower than the maximum limits of residues permitted in natural water by the Brazilian Environmental Agency, 100 µg L−1 (100 ppb), and around the values obtained using other electrodic surfaces or high-performance liquid chromatography, traditionally used in triazine levels determination. Furthermore, the recovery percentages in pure electrolyte and natural waters were around 100%, demonstrating that the methodology proposed is suitable for determining triazines contamination in natural water samples, based on an environmentally friendly procedure.

Rapid and straightforward electrochemical approach for the determination of the toxic food azo dye tartrazine using sensors based on silver solid amalgam

The research paper reports for the first time the investigation of the electrochemical reduction of the synthetic food azo dye tartrazine (TZ) on three different types of silver solid amalgam electrodes (AgSAEs), in particular, the polished one (p-AgSAE), covered by mercury film (f-AgSAE) or by mercury meniscus (m-AgSAE), and the comparison with dropping mercury electrode. The highest reduction peak of TZ on AgSEAs was obtained in the Britton-Robinson buffer (pH 3.4). It was shown that the accumulation step can considerably increase the peak height of TZ reduction. Two adsorptive stripping voltammetric techniques, the linear sweep (LS-AdSV) and the differential pulse (DP-AdSV), were used to develop the simple, rapid, and sensitive methods for the determination of TZ based on its reduction on the working AgSAE. The results showed that all three AgSAEs can be applied for electroanalysis of TZ, however, the best limit of detection (0.078 μmol L−1) and the limit of quantification (0.24 μmol L−1) were obtained for m-AgSAE using LS-AdSV. The developed procedures were successfully applied for TZ determination in soft drink, succade, and veterinary drug using a standard addition method. Therefore, the AgSAEs have been demonstrated to be beneficial electrochemical tools for food products’ quality and safety monitoring.

A New Approach in the Electrochemical Determination of Folic Acid in Foods: Use of a Polished Silver Solid Amalgam Electrode

A New Approach in the Electrochemical Determination of Folic Acid in Foods: Use of a Polished Silver Solid Amalgam Electrode

Electrochemical behavior of methylene blue at bare and DNA-modified silver solid amalgam electrodes

Electrochemical behavior of methylene blue at bare and DNA-modified silver solid amalgam electrodes

Highly Sensitive Determination of Tenofovir in Pharmaceutical Formulations and Patients Urine-Comparative Electroanalytical Studies Using Different Sensing Methods.

This paper discusses the electrochemical behavior of antiviral drug Tenofovir (TFV) and its possible applicability towards electroanalytical determination with diverse detection strategies using square-wave voltammetry. Namely, oxidation processes were investigated using glassy carbon electrode with graphene oxide surface modification (GO/GCE), while the reduction processes, related to the studied analyte, were analyzed at a renewable silver amalgam electrode (Hg(Ag)FE). Scanning electron microscopy imaging confirmed the successful deposition of GO at the electrode surface. Catalytic properties of graphene oxide were exposed while being compared with those of bare GCE. The resultant modification of GCE with GO enhanced the electroactive surface area by 50% in comparison to the bare one. At both electrodes, i.e., GO/GCE and Hg(Ag)FE, the TFV response was used to examine and optimize the influence of square-wave excitation parameters, i.e., square wave frequency, step potential and amplitude, and supporting electrolyte composition and its pH. Broad selectivity studies were performed with miscellaneous interfering agents influence, including ascorbic acid, selected saccharides and aminoacids, metal ions, non-opioid analgesic metamizole, non-steroidal anti-inflammatory drug omeprazole, and several drugs used along with TFV treatment. The linear concentration range for TFV determination at GO/GCE and Hg(Ag)FE was found to be 0.3–30.0 µmol L–1 and 0.5–7.0 µmol L–1, respectively. The lowest LOD was calculated for GO/GCE and was equal to 48.6 nmol L–1. The developed procedure was used to detect TFV in pharmaceutical formulations and patient urine samples and has referenced utilization in HPLC studies.

Application of silver solid amalgam electrodes in electrochemical detection of DNA damage.

In this study, a mercury meniscus-modified silver solid amalgam electrode was used for the first time for the detection of UV-induced DNA damage. The integrity of the double-stranded DNA (dsDNA) layer was detected indirectly using the evaluation of the methylene blue reduction within its accumulation into dsDNA after the UV irradiation of the biosensor surface with two different wavelengths (254nm and 365nm), monitored by differential pulse voltammetry. Moreover, a simple electrochemical characterization of the biosensor surface was performed using cyclic voltammetry of the redox indicator hexaammineruthenium chloride (RuHex) present in the solution. Electrochemical impedance spectroscopy (EIS) was used in both cases for the verification of results. Individual electrochemical signals depend on the time of biosensor exposure to UV irradiation as well as on the selected wavelengths and are different for both used types of dsDNA (salmon sperm and calf thymus). The highest degradation degree up to 60% was observed using sensitive EIS of methylene blue after 10min irradiation of the biosensor at 254nm. The use of RuHex seems to be less sensitive for the detection of dsDNA structural changes, when the degradation degree up to 40% was observed, using EIS at the same conditions.

Voltammetric determination of sulfur in biodiesel microemulsion using a silver solid amalgam electrode.

Monitoring sulfur in biodiesel is of fundamental importance because even in low concentrations, it can harm the operation of the engine parts and increase the emission of toxic gases and particulate material. Hence, a simple, quick and sensitive adsorptive stripping voltammetry (AdSV) method based on a silver solid amalgam electrode (AgSAE) was developed to determine sulfur in biodiesel. The novel electrochemical method was evaluated through the linear sweep adsorptive stripping voltammetry (LSAdSV), square wave adsorptive stripping voltammetry (SWAdSV) and differential pulse adsorptive stripping voltammetry (DPAdSV) in a NH3/NH4+ buffer solution (pH 9.0), containing Na2SO3. The method was applied in biodiesel microemulsion samples under optimal conditions. To this end, a ternary phase diagram was constructed, employing three components: biodiesel/propan-1-ol/buffer solution. The microemulsion with the best response was found to be 25% NH3/NH4+ buffer (pH 9.0), 5.0% biodiesel and 70% propan-1-ol. The method reached a detection limit in the order of 10-7 mol L-1 of sulfur, and recovery values between 80% and 116%. The method was applied in the determination of sulfur in biodiesel, and the amount in the samples was found to be below the value stipulated by the regulatory agencies. The method can be a promising alternative for determining sulfur in the microemulsion of biodiesel, with the ability to provide a fast response regarding the quality of this biofuel.

The Alternative Voltammetric Method for the Determination of Nicotine and Its Metabolite Nicotine N-Oxide

In the present paper, for the first time, the electrochemical behaviour of nicotine metabolite nicotine N-oxide (NNO) on static mercury dropping electrode (SMDE) and mercury meniscus modified silver solid amalgam electrode (m-AgSAE) has been reported. Nicotine N-oxide is reduced forming one peak at the potential −0.78 V on SDME and −0.86 V on m-AgSAE in Britton-Robinson buffer medium at pH 4.5 using cyclic voltammetry (CV). One electron and one proton take part in the reaction of NNO reduction. Calibration graphs for NNO determination using linear sweep voltammetry (LSV) on SDME and square-wave voltammetry (SWV) and differential pulse voltammetry (DPV) on m-AgSAE were obtained. Limit of detection (LOD) is 0.13 μM on SDME, and 0.16 μM (SWV) and 0.29 μM (DPV) on m-AgSAE. Since NNO can be used as an analytical form for nicotine voltammetric determination, so the developed methods were applied for the analysis of pharmaceutical preparations, and the recoveries from 97.3% to 104.6% were achieved. Also, the elaborated methods were used in the analysis of biological fluids, and tobacco products. The obtained results were compared to those indicated in the certificates of drugs analysis, and to the results, obtained by reference methods (HPLC and GC).

Mediatorless electrocatalytic oxygen reduction with catalase on mercury–gold amalgam microelectrodes

Catalase is known for its ability to catalyze disproportionation of hydrogen peroxide into oxygen and water. This work reports the oxygen reduction reaction (ORR) catalyzed by catalase, with a decreased activation energy manifested by a positive shift (+0.2 V) in onset potential. Direct bioelectrocatalysis with bovine liver catalase on a mercury–gold amalgam microelectrode is demonstrated. The background oxygen reduction reaction on the amalgam surface is inhibited by the protein, while the hydrogen evolution reaction (HER) is facilitated. Catalase molecules whose prosthetic groups are not wired to the electrode retain their intrinsic activity towards disproportionation of H2O2 generated at the electrode. The Hg–Au amalgam electrode may also be used to detect dissolved catalase in the absence of its substrate (H2O2) in the solution.

Enhancing the mediated electrochemical reduction process combined with developed liquid-gas electrochemical flow sensors for sustainable N2O removal at room temperature

New electrocatalysts with high reduction efficiency are needed to upgrade the mediated electrochemical reduction for real applications. In addition, automation is required to quantify active electrocatalysts in alkaline media and air pollution. In this study, N2O was removed sustainably by electrogenerated low valent nickel(I) phthalocyanine tetrasulfonate [Ni(I)TSPc] in 1 M KOH using an electroscrubbing system. Ni(I)TSPc electro generation and N2O removal were automated by two (liquid/gas) electrochemical flow sensors, respectively. The Ni(I)TSPc was generated electrochemically up to 95% in 1 M KOH, and high removal efficiency (100%) was observed for 5 ppm N2O and 90% for 10 ppm N2O. A limiting potential change in the in-situ LSV of the chemically synthesized Ni(I)TSPc was taken and derived from the calibration plot and validated by an ex-situ potentiometric titration using an oxygen reduction potential electrode. Using the obtained calibration plot, electrogenerated Ni(I)TSPc allowed a direct determination in a liquid flow cell. The gas flow sensor developed using a KOH/Ni(II)CN4 (TCN (II))-fabricated silver solid amalgam electrode showed an excellent response to N2O concentrations up to 32 ppm. A calibration plot with known concentration was derived and validated by gas chromatography. The response time and sensitivity obtained were approximately 500s and −0.012 mA ppm−1 cm−2, respectively. The sensor stability test confirmed its good stability. Finally, the developed in-situ electrochemical flow sensors were applied to the sustainable automation of N2O pollutant removal.

Screen-printed amalgam electrodes

Silver amalgam screen-printed electrodes (AgA-SPEs) were designed, prepared and tested for the first time as perspective representatives among SPEs that allow measuring at high negative potentials. For this purpose, the precise electrochemical (coulometric) preparation procedure for mercury deposition at the silver working electrode surface of the commercial silver-SPE was developed and a universal method of preparing amalgam electrodes from different metal-SPEs was described. An optimal electrolyzer construction for the mercury deposition, electrolyte composition, electrolysis potential, and a way to activate the electrode surface for its uniform coverage by mercury were proposed. The effect of the mercury content in amalgam on the potential of hydrogen evolution (PHE) at AgA-SPEs was investigated. The maximum PHE value (−1979 ± 4 mV; RSD = 0.17 %; N = 5) was found on AgA-SPE with 50 % (w/w) of Hg content in 0.1 mol L−1 NaOH, which is more negative than in the case of the original silver-SPE for 387 mV (−1592 ± 12 mV; RSD = 0.69 %; N = 5). Determination of the iodine content in iodinated table salt was used for the AgA-SPEs practical testing. Measurement parameters were optimized for three electrochemical cell arrangements: i) the electrodes area of AgA-SPE was covered by 50 μL of the sample solution and differential pulse voltammetric (DPV) measurements were carried out; ii) 3-electrode batch arrangement with only working electrode from AgA-SPE connected with an analyzer for DPV-measurements; iii) amperometric measurements in a flow system. The results of iodine analysis by all three methods were consistent with the manufacturer declared values.

Enhanced sustainable electro-generation of a Ni (I) homogeneous electro-catalyst at a silver solid amalgam electrode for the continuous degradation of N2O, NO, DCM, and CB pollutants

This paper reports the sustainable and enhanced generation of a Ni(I) active electro-catalyst using AgSAE as a cathode material for the sustainable degradation of N2O, NO, dichloromethane (DCM), and chlorobenzene (CB) by electroscrubbing in a series operation. The AgSAE electrode showed 1.66 times higher Ni(I) formation than the Ag metal electrode. The AgSAE achieved 20% ± 2% Ni(I) generation in a highly concentrated alkaline medium, whereas Ag metal only achieved 12% ± 2% Ni(I) generation at the same current density. Electrochemical impedance spectroscopy and voltammetric studies determined that the kinetics of the charge-transfer reaction was also preferential at the AgSAE, with the cathodic peak at −1.26 V vs. Ag/AgCl confirming Ni(I) formation. Initially, the change in the oxygen reduction potential and reduction efficiency of Ni(I) confirmed the removal of N2O, NO, DCM and CB. In addition, the gas Fourier transform infrared (FTIR) spectrum revealed 99.8% removal efficiency of toxic pollutants. Therefore, the regeneration of Ni(I) confirmed the sustainable removal of toxic pollutants. Furthermore, the FTIR spectra revealed the formation of NH3 during the reduction of N2O and NO. On the other hand, DCM and CB were reduced to benzene derivatives in the solution phase. In addition, a plausible reduction mechanism was derived. As a result, the AgSAE cathode exhibited two-fold higher removal efficiency of N2O, NO, DCM, and CB than the previously reported electrodes.

Preparation of a New Copper/Mercury‐Based Amalgam Electrode with Minimal Mercury Content and Its Application for the Determination of Azathioprine in Biological Fluids

AbstractHerein, a new copper/mercury‐based amalgam electrode with 45 wt % copper was introduced. An amalgam electrode with the lowest mercury content among all amalgam electrodes, reported so far,was introduced. The method of making and activating the electrode was investigated and the working conditions were established. The as‐prepared electrode was employed to determine azathioprine(Aza) using differential pulse adsorptive stripping voltammetry (DPASV) method. The required factors were considered for the electrode voltammetric response to evaluate and optimize Aza level. The proper response of this electrode was obtained in Brinton‐Robinson buffer(BRB) (pH 2) at −0.15 V for 200 seconds. The electrode response to the target compound was linear in the concentration range from 0.04 to 1.0 μM. The detection limit was found to be about 1.6×10−8 M. The relative standard deviation (RSD) for 5 determinations was obtained to be about 3.5 % (the average of RSDs calculated for all concentrations, represented in the calibration curve). The method was successfully applied for Aza determination in plasma and urine samples which led to satisfactory results. It can be concluded that the presence of high levels of potential interfering agents such as ascorbic acid and cysteine did not affect the Aza determination.

Ultrasensitive determination of selenium in foodstuffs and beverages using an electroanalytical approach

This work describes the development of an electroanalytical methodology to the determination of nanomolar levels of selenium, which is sensitivity, selectivity, simple, low cost, quickness, and robustness. Therefore, it was employed a silver solid amalgam electrode modified by a thin and stable mercury film (f-AgSAE) allied to square-wave cathodic adsorptive stripping voltammetry (SWCASV). Besides this, the adsorptive and square-wave voltammetry parameters were previously optimized following the built of analytical curves in the linear range from 1.00 × 10−7 to 8.00 × 10−6 mol L−1, that resulted in a correlation coefficient of 0.9989, repeatability of 1.64%, reproducibility of 4.90%, detection limit of 1.01 × 10−9 mol L−1 and quantification of 3.36 × 10−9 mol L−1. This methodology proposed can be compared with similar data obtained by sophisticated spectroscopic techniques and other electroanalytical techniques. The procedure proposed was applied to selenium determination in in natura food (apple, orange, potato, spinach and tomato) and beverage (coconut water, soy juice and soy milk) samples. These samples were digested using a simple procedure that resulted in very satisfactory recovery percentages, confirming suitable robustness of the proposed methodology.

Long-term stable and selective conversion of carbon dioxide to formate using dental amalgam electrode

The process of electrochemical conversion of CO2 to a valuable chemical requires the use of an electrode material with high selectivity and stability. In this study, we successfully fabricated a dental amalgam composition on a copper foam electrode and demonstrated the selective conversion of CO2 to formate. The faradaic efficiency was 80–100 % at current densities ranging from 50 to 250 mA∙cm−2. The residual electricity was used solely to produce H2, and all the carbon atoms in CO2 were converted to formate. It enabled the easy separation of the highly water-soluble formate from the gaseous hydrogen. The produced formate concentration was up to 2.4 M (18 wt%), and the electrolyzer based on the dental amalgam electrode was effectively operated both continuously and intermittently for over a month. The results demonstrated the feasibility of the economic and large-scale CO2-to-formate conversion process.

Electrochemical Determination of Trifluralin Herbicide Using Silver Solid Amalgam Electrode: Application in Fresh Food Samples

This paper reports the use of polished silver solid amalgam electrode (p-AgSAE) allied to square wave voltammetry (SWV) in the development of a simple, sensitive, fast and green electroanalytical methodology for the trifluralin herbicide determination in fresh food samples. The experimental (supporting electrolyte and potential and time accumulation) and voltammetric (pulse frequency, pulse amplitude and scan increment potential) parameters were previously optimized, which were employed in the construction of analytical curves. Therefore, these curves have enabled the calculation of analytical parameters (linearity range, equation of the analytical curves, coefficients of determination, limits of detection and quantification, recovery efficiency, and relative standard deviations for intraday and interday experiments) and they indicated that the use of the p-AgSAE is suitable for determining any contamination by trifluralin. So, the proposed methodology had to minimize the toxic residues due to the use of liquid mercury or the adsorbed products from the redox reaction that promotes passivation in the other solid surfaces. Furthermore, the optimized methodology was used to trifluralin determination in eggplant, carrot, tomato, grape juice and orange juice, and the results indicated that the proposed methodology presented high robustness, stability and sensitivity, good reproducibility, and hence it is applicable for complex samples.

Voltammetric Behavior and Reliable Method for the Determination of Coccidiostat Robenidine in Animal Feed and Poultry Meat

AbstractThe voltammetric behaviour of coccidiostat robenidine was investigated. The outcomes have revealed that reduction of robenidine causes an appearance of one diffusion‐controlled cathodic peak on a static mercury drop electrode (SMDE) and a silver solid amalgam electrode (p‐AgSAE). The influence of pH, a supporting electrolyte, a scan rate and accumulation parameters was evaluated. The mechanism of robenidine reduction involving two electrons and one proton was studied for the first time. The calibration curves with the wide linear concentration ranges (more than two concentration orders) were obtained under optimized experimental conditions and operating parameters. The reduction current linearly increases when increasing the concentration of coccidiostat. The methods of voltammetric determination of robenidine in feed and meat have been developed. The limits of quantitation of the methods of robenidine determination in feed are 9.5 mg/kg and 2.5 mg/kg on SMDE and p‐AgSAE, respectively. Calculated recoveries ranges of robenidine were between 88.8 % and 101.5 %.

Determination of heavy metal poisoning antidote 2,3-dimercapto-1-propanesulfonic acid using silver solid amalgam electrode

Voltammetric behavior of heavy metal poisoning antidote 2,3-dimercapto-1-propane-sulfonic acid (DMPS) was investigated using linear scan voltammetry (LSV), differential pulse cathodic stripping voltammetry (DPCSV), differential pulse anodic stripping voltammetry (DPASV), and elimination voltammetry with linear scan (EVLS) at a polished (p-AgSAE) and at a meniscus modified (m-AgSAE) silver solid amalgam electrode. It was confirmed that the mechanism of the electrode process involves two consecutive reductive desorptions with coupled proton/electron transfer preceded by a kinetic process prominent at higher scan rates as revealed by EVLS. Voltammetric and complexation behavior of DMPS in the presence of Pb2+ was further investigated by DPASV and DPCSV titrations confirming reductive desorption, complex formation, and transmetalation. Optimum conditions for DPCSV were as follows: Britton-Robinson buffer (BRB) of pH 10, Eacc = −200 mV and tacc = 30 s for p-AgSAE and BRB of pH 5, Eacc = 0 mV and tacc = 15 s for m-AgSAE. Limits of quantification (LOQs) and detection (LODs) were 0.3 and 0.1 μmol L−1 at m-AgSAE and 0.8 and 0.3 μmol L−1 at p-AgSAE, respectively. The practical applicability of the newly developed method was verified by determination of DMPS in commercial drug Dimaval and in human urine samples.