Meniscus Modified Silver Solid Amalgam Research Articles

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.

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).

Electrochemical microcell based on silver solid amalgam electrode for voltammetric determination of pesticide difenzoquat

This study presents an application of a non-toxic mercury meniscus modified silver solid amalgam electrode as a reliable, user-friendly and sensitive sensor for the determination of herbicide difenzoquat as a model pollutant in micro volumes of samples. Difenzoquat gave one cathodic peak at around –1.4 V (vs. Ag/AgCl/3 mol L–1 KCl reference electrode) independent on pH (in the range 8–12). Sharp maxima greatly influenced the peak of the analyte and they were eliminated by the addition of gelatine as a surface-active compound. The optimal supporting electrolyte was found to be Britton-Robinson (BR) buffer with pH 12. Determination of the analyte in the 10 μL volume was carried out in a newly developed simple microcell with the amalgam working electrode. A procedure for fast and reliable removal of dissolved oxygen was used. Difenzoquat was therefore successfully determined by differential pulse voltammetry in BR buffer pH 12 and in model river water samples with addition of gelatine with limits of quantification 0.41 and 0.45 μmol L–1, respectively. It was proved that this sensor can be directly used for monitoring of pollutants in volumes of tens of microliters of various samples with similar parameters as the determination in larger volumes.

Reduction behavior of insecticide azoxystrobin and its voltammetric determination using silver solid amalgam electrode

Electrochemical reduction of systemic fungicide azoxystrobin, used to protect a wide variety of crops, was investigated using cyclic voltammetry with a mercury meniscus-modified silver solid amalgam electrode (m-AgSAE). The mechanism of the electrochemical reduction was proposed and supported with high-performance liquid chromatography/mass spectrometry analysis of azoxystrobin solutions electrolyzed on mercury pool electrode. An analytical method for the determination of azoxystrobin by differential pulse voltammetry with m-AgSAE was developed. A wide linear dynamic range (2.0 × 10−6–5.0 × 10−5 mol dm−3) and low limit of detection (7 × 10−7 mol dm−3) were obtained. The accuracy and repeatability of the proposed method were evaluated by the analysis of model solutions with recovery from 96.0 to 104.0% and relative standard deviation of 5 repeated determinations < 3.5%. Finally, a new voltammetric method using m-AgSAE was successfully applied for azoxystrobin determination in real samples, concretely in spiked river water and pesticide preparations.

Voltammetric Determination of Aclonifen at a Silver Amalgam Electrode in Drinking and River Water

Abstract A method for the determination of pesticide Aclonifen (AC) in drinking and river water by differential pulse voltammetry (DPV) on a meniscus modified silver solid amalgam electrode (m-AgSAE) using solid phase extraction (SPE) as a cleanup and preconcentration procedure is described. The limit of detection (LOD) for direct DPV determination of AC in deionized water is 2.7·10-8 mol·dm-3. LOD for DPV determination of AC in tap water after SPE is 1.6·10-10 mol·dm-3, the recovery being 55%. LOD for the determination of AC in Vltava river water is 1.9·10-9 mol·dm-3, the recovery being 65%. Humic acids interfere with the determination in river water; this problem can be resolved by adjusting the pH of the extracted sample to 6. The advantages of this approach are high sensitivity, low LOD, quick and easy sample preparation and fast determination.

Voltammetric determination of trace amounts of diacetyl at a mercury meniscus modified silver solid amalgam electrode following gas-diffusion microextraction

A new approach was developed for the determination of trace amounts of diacetyl in food products using gas-diffusion microextraction (GDME) and subsequent detection by differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE). Diacetyl is a vicinal diketone responsible for the buttery aroma in many fermented foods and beverages. Its determination is important not only for evaluation of the final product quality (note of mention: health related concerns were associated with continuous diacetyl exposure) but also to monitor fermentation. GDME, a technique combining gas-diffusion and microextraction, particularly aimed to volatile and semi-volatile analytes, seemed the best way to selective extract diacetyl. A solution of 0.05% o-phenylenediamine (OPDA) prepared in a Britton-Robinson buffer (pH 5.0) was chosen as the extracting solution. This solution simultaneously extracts, pre-concentrates and derivatizes diacetyl to 2,3-dimethylquinoxaline (DMQ), enhancing the extraction selectivity and making the analyte electroactive. After finding the optimum conditions for the extraction process (10min at 60°C with 1.0mL of OPDA at pH 5.0), the DPV measurements at the m-AgSAE were conducted with a scan rate of 7mVs−1, a modulation amplitude of 50mV and a modulation time of 100ms. Under these conditions, the resulting DMQ could be easily measured at a potential of −0.6V vs. Ag|AgCl (3molL−1 KCl). The amalgam electrode keeps the advantages of classic mercury electrodes, like high sensitivity, while being environmentally friendly. The GDME/m-AgSAE produced suitable method features for the determination of low amounts of diacetyl (as DMQ) in alcoholic beverages, and in fact, to the best of our knowledge, the limit of quantification of 0.18µgL−1 is one of the lowest reported in literature.

Voltammetric determination of sodium anthraquinone-2-sulfonate using silver solid amalgam electrodes

Voltammetric determination of sodium anthraquinone-2-sulfonate (AQ) was investigated at a polished silver solid amalgam electrode (p-AgSAE) and at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) (inner diameter of both 0.5 mm). The reaction mechanisms of AQ at p-AgSAE and at m-AgSAE were studied by cyclic voltammetry, direct current voltammetry, and by elimination voltammetry with linear scan. Limits of detection obtained by differential pulse voltammetry were 1 × 10−6 mol dm−3 for p-AgSAE and 4 × 10−7 mol dm−3 for m-AgSAE. Both electrodes were successfully applied for differential pulse voltammetry of AQ in model samples of deionized water, river water, and human urine.

Comparison Study of Voltammetric Behavior of Muscle Relaxant Dantrolene Sodium on Silver Solid Amalgam and Bismuth Film Electrodes.

Voltammetric behavior of muscle relaxant dantrolene sodium (DAN) was studied and the voltammetric methods for its determination using polished and mercury meniscus modified silver solid amalgam electrodes (p-AgSAE and m-AgSAE) as well as using bismuth film electrode (BiFE, ex situ plating on GCE) have been proposed. These working electrodes represent the most commonly used alternatives to mercury ones which come wrongfully into disfavor because of alleged toxicity of mercury. Within this work, the obtained results of DAN determination have been completed by corresponding statistical parameters and also some electrochemical characteristics of AgSAEs and BiFE were assessed, especially in comparison with the mercury electrodes.

Investigation of Voltammetric Behaviour of Insecticide Chlorpyrifos on a Mercury Meniscus Modified Silver Solid Amalgam Electrode

This paper is devoted to the study of electrochemical behaviour of insecticide chlorpyrifos with proved endocrine disruptor properties and to the finding of the optimum conditions for its determination using differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE). It was confirmed that the electrochemical reaction is based on the reduction of H+ ions catalysed by chlorpyrifos adsorbed on the surface of the m-AgSAE. Two variants of the m-AgSAE were tested: i) freshly prepared m-AgSAE for each set of measurements with a classical previously published electrochemical activation (5min at −2.2V in 0.2mol.L−1 KCl under stirring and in the presence of oxygen) for which the optimal base electrolyte was found to be the acidic part of the Britton-Robinson (BR) buffer (pH 1.82) containing 15% of methanol and ii) freshly prepared m-AgSAE for each set of measurements with a newly developed simplified electrochemical activation (10s at −2.2V in the stirred base electrolyte alone in the presence of oxygen) for which the optimal base electrolyte was found to be the acidic part of the BR buffer (pH 1.82) containing 30% of methanol.

A miniaturized electrode system for voltammetric determination of electrochemically reducible environmental pollutants

A newly designed miniaturized electrode system (MES) based on a mercury meniscus modified silver solid amalgam electrode as the working electrode was developed for voltammetric determination of electrochemically reducible organic compounds in small sample volumes. Genotoxic 2-aminofluoren-9-one (2-AFN) was chosen as a model environmental pollutant in this study to test the performance of the introduced MES. The determination of 2-AFN was carried out by differential pulse voltammetry in 100μL samples under following conditions, using two different ways of air oxygen removal: (i) a supporting electrolyte methanol–Britton–Robinson (BR) buffer of pH 4.0 (1:9, v/v), with regeneration potentials Ereg,1=0mV and Ereg,2=−1200mV and with oxygen removal by bubbling with nitrogen, and (ii) a supporting electrolyte methanol–BR buffer of pH 10.0 (1:9, v/v), with regeneration potentials Ereg,1=−200mV and Ereg,2=−1600mV and with oxygen removal by the addition of solid sodium sulfite as a reducing agent. The calibration curves were measured in the concentration range from 1 to 100μmolL−1 of 2-AFN, with the limits of quantification about 1μmolL−1 reached in both media. The practical applicability of the newly developed voltammetric methods using the MES was successfully verified on the direct determination of 2-AFN in model samples of drinking and river water.

Voltammetric determination of fenitrothion and study of its interaction with DNA at a mercury meniscus modified silver solid amalgam electrode

A mercury meniscus modified silver solid amalgam electrode was used for the first time for the determination of submicromolar concentrations of fenitrothion (FNT). The medium of ethanol–Britton–Robinson buffer of pH 7.0 (1:9) was chosen as the optimal one. The newly developed direct current and differential pulse (DP) voltammetric methods are fast, reliable, and robust. Moreover, the applicability of the DP voltammetric method was verified for the determination of FNT in spiked samples of drinking and river water, with the limits of quantification in the concentration order of 10−7 mol dm−3. Furthermore, the interaction of FNT with double-stranded (ds) DNA was investigated directly in a solution. From changes in the FNT electrochemical signals, we assume a formation of a FNT–dsDNA complex in which FNT bounds to dsDNA by electrostatic forces. DP voltammetry was employed to probe this interaction, while cyclic voltammetry was used for the investigation of voltammetric data of free FNT and FNT bound to dsDNA.

Voltammetry of benzodiazepines on meniscus-modified silver solid amalgam electrode

This paper describes voltammetric behavior of 1,4-benzodiazepines (BDZs) on meniscus-modified silver solid amalgam electrode with aim of their determination. Cyclic voltammetry was used for the study of electrochemical behavior (reversibility, adsorption-diffusion process, and charge transfer coefficient) of BDZs. Differential pulse voltammetry was utilized for proposing reaction mechanism, finding supporting electrolyte with optimal pH, and determining diazepam in urine. The pH effect was studied in different media (Britton-Robinson, phosphate, citrate buffer, and 0.1 mol dm−3 NaOH). The calibration dependences exhibited good linearity in the range from 10−7 to 10−4 mol dm−3 under the optimum pH conditions. The advantage of the developed methods was simple, fast, and low-cost procedure for the determination of BDZs. The developed method was successfully used for the diazepam determination in the model sample of urine. The proposed method exhibits the recovery 97.8 % with standard deviation of 2.28 %.

Voltammetric detection of phytochelatin transported across unmodified and protoplast modified model phospholipid membranes

Possibility of phytochelatin PC2 transport was examined using developed electrochemical cell with two compartments separated by a phospholipid membrane created in pores of polycarbonate support. At first cell penetrating peptides (transportan 10 and mastoparan X) were used to allow the transfer of phytochelatin PC2. The results demonstrated that transportan 10 is several times more efficient than mastoparan X for transferring of phytochelatin across model membrane. Voltammetry with hanging mercury drop electrode or with solid amalgam electrodes was applied for detection of transported species. For determination of PC2, hanging mercury drop electrode and mercury meniscus-modified silver solid amalgam electrode were suitable. Modified model phospholipid membrane was prepared with parts of protoplasts from barley roots or leaves, and transport of phytochelatin PC2 has been confirmed. Electrochemical impedance spectroscopy was utilized to monitor formation, stability, and qualitatively the transporting process across the supported phospholipid membranes.

Application of silver solid amalgam electrode for determination of formamidine amitraz

The voltammetric behavior of pesticide amitraz was investigated at polished silver solid amalgam electrode (p-AgSAE) and at mercury meniscus modified silver solid amalgam electrode (m-AgSAE) (inner diameter 0.5 mm). The results were compared with those obtained using hanging mercury drop electrode. The reaction mechanism was studied by direct current voltammetry and elimination voltammetry with linear scan. Optimum conditions for determination using differential pulse adsorption stripping voltammetry of this compound were found in Britton–Robinson buffer mixed with ethanol (4:1 v/v). The limits of detection were calculated as 8.9 × 10−9 mol dm−3 (with t acc = 20 s) for m-AgSAE and as 0.168 × 10−6 mol dm−3 (with t acc = 20 s) for p-AgSAE. The proposed method was successfully applied for determination of amitraz in real samples of river water.

Sensitive voltammetric method for determination of herbicide metribuzin using silver solid amalgam electrode

New sensitive voltammetric method for determination of triazinone herbicide metribuzin (MTZ) was developed employing polished and mercury meniscus-modified silver solid amalgam electrode (p-, m-AgSAE). MTZ yielded two reduction signals on both used working electrodes in acidic and slightly acidic media and the positively situated peak [at about −650 mV vs. Ag|AgCl|KCl (sat.)] was found suitable for further analytical measurements. The highest responses were recorded in Britton–Robinson buffer of pH 2 (p-AgSAE) or 3 (m-AgSAE). Various voltammetric techniques like cyclic, linear sweep, and differential pulse voltammetry were used for examination of the voltammetric behavior of MTZ. Parameters of differential pulse voltammetry were optimized and low detection limits were reached (LODm-AgSAE = 6.0 × 10−8 mol dm−3 and LODp-AgSAE = 7.5 × 10−8 mol dm−3). Moreover, excellent repeatability of determination and measurements as well was confirmed by low values of relative standard deviations of five repeated determinations [RSD (5) ≤ 6.0 %] and of 11 repeated measurements [RSD (11) ≤ 4.5 %], respectively. Finally, practical applicability of newly proposed methods was verified by the analysis of spiked tap and river water and by determination of MTZ in pesticide preparation with excellent results. All the obtained results were compared with those gained for classic mercury electrode.

The Use of the Silver Solid Amalgam Electrode for Voltammetric Determination of 9-nitroanthracene

ABSTRACTThe voltammetric behavior of 9-nitroanthracene was investigated at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE; inner diameter of 0.5 millimeter) by differential pulse voltammetry (DPV) and adsorptive stripping DPV (DPAdSV). Optimum conditions were found for the determination of this analyte in Britton-Robinson buffer (pH = 10.5): pulse width of 80 milliseconds, pulse height of −50 millivolts, initial potential (Ein) = −100 millivolts, final potential (Efin) = −1200 milivolts, potential of accumulation (Eacc) = −100 millivolts, scan rate of 20 millivolts per second. The limit of detection was found to be 0.7 nanomole per liter (tacc = 60 seconds) by DPAdSV at m-AgSAE. The method was successfully applied for the determination of 9-nitroanthracene in drinking and river water.

Voltammetric Behavior of the Insecticide Pymetrozine on a Mercury Meniscus Modified Silver Solid Amalgam Electrode

ABSTRACTA novel sensitive voltammetric method for the determination of the insecticide pymetrozine was designed using a solid working electrode. A mercury meniscus modified silver solid amalgam electrode in connection with differential pulse voltammetry was found to be appropriate for the determination of the insecticide. Pymetrozine provided one well-developed reduction peak suitable for analytical purposes at approximately −800 millivolts (vs. the Ag/AgCl electrode) in an acidic medium. The voltammetric behavior of pymetrozine as a function of the pH of the supporting electrolyte and scan rate was investigated using cyclic voltammetry and direct current voltammetry, respectively. The optimum conditions for determination using differential pulse voltammetry were in a Britton-Robinson buffer at pH 3.0 with a limit of detection of 5.4 × 10−8 moles per liter and a linear dynamic range from 2 × 10−7 to 1 × 10−4 moles per liter. The relative standard deviations of repeated determinations (n = 5) at various concentrations of pymetrozine did not exceed 3%. The results obtained using a silver solid amalgam electrode were compared with those achieved on hanging mercury drop electrode. The influence of possible interfering agents was also studied. The practical application of the method was verified by analysis of pesticide preparations and fortified river water.

Voltammetric Analysis of Herbicide Picloram on the Silver Solid Amalgam Electrode

ABSTRACTA silver solid amalgam electrode was employed for the first time for the determination of the pyridine herbicide picloram. The voltammetric behavior of this herbicide was studied using cyclic, direct current, and differential pulse voltammetry on the mercury meniscus modified silver solid amalgam electrode. All results were compared with those achieved on the classic hanging mercury drop electrode. One reduction signal, which was suitable for analytical purposes, was recorded on the amalgam electrode after addition of picloram. The current response of the herbicide increased linearly in the concentration range from 1 × 10−7 to 8 × 10−5 moles per liter, and a limit of detection of 8.78 × 10−8 moles per liter was obtained using differential pulse voltammetry under the optimized conditions. The selectivity and applicability of the voltammetric technique was verified by an interference study and analysis of fortified environmental samples with excellent recoveries: 100.0%(tap water), 100.5% (dam water), and 95.0% (river water).

Green electrochemical sensors based on boron-doped diamond and silver amalgam for sensitive voltammetric determination of herbicide metamitron

Novel sensitive voltammetric methods for determination of herbicide metamitron were developed using polished and mercury meniscus-modified silver solid amalgam electrode (p-, m-AgSAE) and boron-doped diamond electrode (BDDE). It was found that metamitron yields one analytically utilizable reduction (AgSAEs) and one oxidation (BDDE) signal. All three tested working electrodes connected to different voltammetric techniques were found to be appropriate for the analysis of the herbicide. The optimum conditions for metamitron determination were ascertained in Britton-Robinson buffer solution of pH 2.0 (m-AgSAE, BDDE) and in 0.05 mol dm−3 H2SO4 (p-AgSAE), respectively, with the limits of detection 3.6 × 10−8 mol dm−3 (m-AgSAE), 1.0 × 10−7 mol dm−3 (p-AgSAE), and 1.2 × 10−6 mol dm−3 (BDDE). Calculated values of relative standard deviations of repeated determinations (n = 5) in various concentration levels of metamitron did not exceed 5 % for either of the tested electrodes. Finally, practical applicability of newly proposed methods was verified by the analysis of pesticide preparation and spiked river water.

Determination of 5-nitroindazole using silver solid amalgam electrode

The voltammetric behavior of 5-nitroindazole was investigated at polished (p-AgSAE) and at mercury meniscus-modified (m-AgSAE) silver solid amalgam electrodes (inner diameter 0.5 mm) by direct current voltammetry and by differential pulse voltammetry. The results were compared with those obtained using hanging mercury drop electrode. Optimum conditions for differential pulse voltammetry determination of 5-nitroindazole were found in Britton-Robinson buffer of pH 8. The reaction mechanism was investigated using direct current voltammetry and elimination voltammetry with linear scan. Differential pulse voltammetry with optimized parameters was applied for determination of the compound in model and real samples. The limits of detection were calculated as 0.14 × 10−6 mol dm−3 for m-AgSAE and as 0.47 × 10−6 mol dm−3 for p-AgSAE. The proposed method was successfully applied for determination of 5-nitroindazole in real samples of river water. .