Renewable Silver Amalgam Film Electrode Research Articles

Electrochemical determination of budesonide: a common corticosteroid used to treat respiratory diseases such as COVID-19 and asthma

The outbreak of the COVID-19 pandemic has adversely affected the most important areas of the modern world. One of the challenges related to counteracting the effects of the pandemic it was necessary to develop methods for the quantitative determination of pharmaceuticals used in the treatment of patients suffering from this disease and its long-term effects. Budesonide (BUD) is a widely available and inexpensive corticosteroid used extensively not only among people suffering from COVID-19, but also asthma and other respiratory diseases. A significant increase in the consumption of drugs containing this component requires the development of new BUD determination methods, especially in real samples. This paper presents a new voltammetric method for BUD determination at renewable silver amalgam film electrode (Hg(Ag)FE). The electrochemical measurements were conduced in the supporting electrolyte containing 80% of methyl alcohol, 0.04 mol L−1 Britton–Robinson buffer (pH 3.0) and 20 mg mL−1 of NaClO4 under optimized differential pulse voltammetry (DPV) parameters. Detailed studies of the behaviour of the BUD on the surface of Hg(Ag)FE demonstrated the quasi-irreversible nature of the diffusion-controlled, two electrons and two protons reduction process. A calibration curve in the range from 1.0 to 290 µg mL−1 shows limit of detection and limit of quantification equal to 0.06 and 0.21 µg mL−1, respectively. The impact of numerous interferences over a wide range of concentrations on BUD signals was analysed and evaluated. The utility of the proposed method was verified by the quantitative analysis of BUD in two pharmaceutical products and the spiked water samples.Graphical abstract

Rapid direct cathodic voltammetric determination of insecticide flonicamid by renewable silver-amalgam film electrode

ABSTRACT The voltammetric characterisation and determination of insecticide flonicamid (N-cyanomethyl-4-(trifluoromethyl)nicotinamide) were performed for the first time using a simple electrochemical sensor, renewable silver-amalgam film electrode (Hg(Ag)FE). During the development of the direct cathodic square wave voltammetric method (SWV) for the determination of flonicamid, a voltammetric behaviour of a target analyte in aqueous Britton-Robinson buffer solution from pH 2.0 to pH 11.98 was examined. In the investigated pH range, the peak which appeared in the potential span between −0.86 V and −1.56 V vs. saturated calomel electrode depending on the applied pH value was chosen for analytical purposes. As optimal pH for the determination of flonicamid, pH 2.5 was selected. Cyclic voltammetric measurements at pH 2.5 confirmed that the electrode reaction mechanism is an irreversible reduction controlled by the diffusion of flonicamid at Hg(Ag)FE. The optimised Hg(Ag)FE-SWV method resulted in good linearity in the concentration range of 1.96–41.2 µg mL−1 while the relative standard deviation of the method was 0.30%. Flonicamid was successfully determined in commercial formulation Teppeki 500 WG® and spiked river water sample by the developed method using the standard addition procedure. The average value of flonicamid amount found in a commercial formulation based on three repetitions was 497.8 ± 0.9 g kg−1, which is in good agreement with the manufacturer’s declaration (500 ± 25 g kg−1) and with comparative high-performance liquid chromatographic measurements with diode array detection where a found average value of flonicamid content was 497.5 ± 11.5 g kg−1. The obtained results also indicate that the developed SWV procedure using Hg(Ag)FE was appropriate for the determination of flonicamid in a spiked river water sample with the recovery of 92.86% and RSD of 6.19%.

Retractable-pen-based renewable silver amalgam film electrode for microliter sample analysis of electrochemically reducible environmental pollutants

A novel, inexpensive, and simple construction of a retractable-pen-based renewable silver amalgam film electrode (RAE) was introduced in this study for electrochemical sensing of electrochemically reducible compounds in small sample volumes. This electrode is based on a mechanical renewal of the amalgam film achieved by using mechanisms found in a common retractable ballpoint pen. Cadmium(II) and two model environmental pollutants (4-nitrophenol (NP) and 3-nitrobiphenyl (NB)) were used to evaluate the performance of the novel RAE and its utilization in the electrochemical microcell. In order to decrease the high variability of observed reduction potentials of NP and NB on RAE, the influence of the content of silver in the amalgam used for the renewal of the film was investigated. It was found that 4 % of Ag in the amalgam improved the repeatability of peak potentials. Obtained limit of quantification (LOQ) for Cd(II) was 54 nmol L–1 (6.1 ppb) in acetate buffer (pH 4.8); LOQ for NP was 1.2 μmol L–1 in Briton-Robinson (BR) buffer (pH 4.0). LOQ for NB was 2.5 μmol L–1 in BR buffer (pH 6.0) – methanol (8:2, v/v) medium. The possibility of further decrease of LOQ of NB to a nanomolar range with the help of the microcell was demonstrated by the liquid-liquid extraction (LLE) to hexane with the preconcentration factor of 1000. Moreover, RAE offers portability, long-term stability, simple renewal of the surface, a wide cathodic potential window, and it can be considered as an inexpensive, robust, and safe alternative to other mercury-based electrochemical sensors.

A novel catalytic adsorptive stripping voltammetric method for the determination of germanium ultratraces in the presence of chloranilic acid and the V(IV)\xb7HEDTA complex

A novel, sensitive catalytic adsorptive stripping voltammetric procedure which can be used to determine trace amounts of germanium is described. The method is based on the interfacial accumulation of the complex formed by Ge(IV) and the product of the reduction of chloranilic acid on the hanging mercury drop electrode or the renewable silver amalgam film electrode, and its subsequent reduction from the adsorbed state followed by the catalytic action of the V(IV)·HEDTA complex. The presence of V(IV)·HEDTA greatly enhances the adsorptive stripping response of Ge. The reduction of the Ge(IV) in the presence of chloranilic acid and V(IV)·HEDTA was investigated in detail and the effects of pH, electrolyte composition, and instrumental parameters were studied. Under optimal conditions, the catalytic peak current of germanium exhibited good linearity for Ge(IV) concentrations in the range of 0.75–60 nM (for 60 s of accumulation at −0.1 V, r2 = 0.995) and a low limit of detection (LOD = 0.085 nM). The procedure was successfully applied to determine Ge in water samples.

Extremely sensitive germanium stripping voltammetric determination with the use of a new Ge(IV)-catechol-V(IV)-HEDTA catalytic adsorptive system

It was found that the addition of V(IV)-EDTA or V(IV)-HEDTA to a solution containing the Ge(IV)-catechol complex induced certain catalytic processes that significantly enhanced the adsorptive stripping voltammetric (AdSV) response of germanium. The catalytic enhancement achieved with V(IV)-HEDTA was determined to be 7.4 times higher than that in the presence of V(IV)-EDTA; the former oxidant was therefore selected for the development of a new, sensitive catalytic adsorptive stripping voltammetric (CAdSV) procedure of germanium quantification. The optimal CAdSV Ge(IV) response was obtained in a 0.05 M acetate buffer with a pH of 4.4, in the presence of 1.0⋅10−3 M of catechol, 1.0⋅10−3 M of V(IV) and 1.5⋅10−3 M of HEDTA. The sensitivity of the new method was 25.2 nA/nM and the catalytic response was linear within the range of 5·10−11 M to 2·10−8 M Ge(IV) for 80 s of accumulation. The limit of detection was found to be 1.0·10−11 M. The reproducibility was equal to 3.0%. Interferences from inorganic ions and surface-active substances were evaluated. The procedure was applied to determine Ge(IV) in mineral water. It was also shown that both the hanging mercury drop electrode and the non-toxic renewable silver amalgam film electrode can be applied for Ge(IV) quantification by means of the elaborated method, with similar performance.

Quantitative determination of the veterinary drug monensin in horse feed samples by square wave voltammetry (SWV) and direct infusion electrospray ionization tandem mass spectrometry (DI–ESI–MS/MS)

This paper presents for the first time the determination of monensin monosodium salt (MnzNa) by means of square wave voltammetry (SWV), cyclic voltammetry (CV), and, in parallel, direct infusion electrospray ionization tandem mass spectrometry (DI–ESI–MS/MS). The influence of various factors, such as pH, buffer composition, and SWV parameters on current response was studied. The best SWV signal was obtained at about −1.50 V versus an Ag/AgCl/KCl reference electrode in Britton–Robinson (B–R) buffer. Under optimal conditions, the SWV response of the renewable silver amalgam film electrode Hg(Ag)FE was linear over two MnzNa concentration ranges, from 7.5 × 10−8 to 5.0 × 10−7 mol L−1 and from 5.0 × 10−7 to 1.0 × 10−5 mol L−1. The limits of detection and quantification were 1.27 × 10−8 mol L−1 and 4.23 × 10−8 mol L−1, respectively. The applicability of the developed SWV method was investigated in the determination of MnzNa in horse feed by the standard addition method. CV was applied to understand the electrode mechanism of MnzNa. Finally, direct infusion electrospray ionization tandem mass spectrometry (DI–ESI–MS/MS) was used to determine MnzNa in horse feed samples by the external calibration method. The detector response was linear in the concentration range of 1.1 × 10−7 to 1.4 × 10−6 mol L−1. The obtained limits of detection and quantification were 3.4 × 10−8 mol L−1 and 1.1 × 10−7 mol L−1, respectively. Statistical analysis of MnzNa determination results from SWV and DI–ESI–MS/MS did not reveal any significant differences between them.

Voltammetric determination of thujone by a renewable silver amalgam film electrode in herbal matrices and thuja oil

Thujone is a ketone and a dicyclic monoterpene which naturally occurs in a variety of common plants, but in large quantities may be toxic for humans. In this work a simple and rapid DPV methodology of thujone determination on renewable silver amalgam film electrode is proposed. It was observed that the reduction of thujone in nitric acid is a quasi-reversible two-electron process, while the reaction was controlled by surface phenomena. Experimental conditions such as composition of the supporting electrolyte and operation parameters were optimized. The promising results were obtained in 0.0115molL−1 HNO3 (pH1.85) and 9.6% ethanol. The calibration graph was linear from 0.7–142mgL−1 with correlation coefficient r=0.9996. Obtained sensitivity was 0.0724μA/mgL−1, while detection limit 0.05mgL−1. In the presence of copper the sensitivity was reduced to 0.0504μA/mgL−1. Procedure was verified using complex herbal matrices spiked by the thujone. Recovery of the low analyte concentration i.e. 0.7–2.1mgL−1 significantly depends on the level of the interferences. A self-referencing strategy of thujone determination in thuja oil was also developed and applied in exploration of thujone without preparation of the sample in commercially available product.

Voltammetric determination of aluminum-Alizarin S complex by renewable silver amalgam electrode in river and waste waters

The direct voltammetric determination of aluminum is difficult because it is reduced at very low potential −1.75V versus Ag/AgCl. Therefore, in this work a simple and rapid stripping voltammetry method of Alizarin S-Al complex determination on renewable silver amalgam film electrode was proposed. The electrode process in complex electrolyte is irreversible and controlled by the surface phenomena. Experimental conditions such as preconcentration time and operation parameters were optimized. The promising results were obtained in 0.1M ammonia buffer, 0.01M KBrO3, 0.25μM Ca, 0.1μM EDTA. The calibration graph was linear from 5 to 45μgL−1 with sensitivity of 14.6μA/mgL−1, detection limit of 0.2μgL−1 and repeatability below 3.5%. With accumulation time of 4s the sensitivity increases to 17.4μA/mgL−1 with r=0.9978 but the range of linearity was limited to 20μgL−1. The problem of the main interferent which is zinc was resolved by the EDTA addition. Procedure was verified using waste waters CRMs with recovery 99–110% and spiked Vistula River water.

Improved electroanalytical characteristics for flumetralin determination in the presence of surface active compound

The use of square wave voltammetry (SWV) and square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a cyclic renewable silver amalgam film electrode for the determination of flumetralin is presented. Poor separation of two overlapped reduction peaks is significantly improved when hexadecyltrimethylammonium bromide is used as a component of the supporting electrolyte solution (together with BR buffer pH 9.5). The SW technique parameters were investigated and found optimal as follows: frequency 50 Hz, amplitude 40 mV, and step potential 5 mV. Accumulation time and potential were studied to select the optimal conditions in adsorptive voltammetry. The analytical curve was linear for the flumetralin concentration range from 1.0 × 10−6 to 1.0 × 10−5 mol dm−3 and from 5.0 × 10−9 to 1.0 × 10−7 mol dm−3 for SWV and SWAdSV, respectively. Detection limit of 6.5 × 10−10 mol dm−3 was calculated for accumulation time 60 s at −0.2 V. The repeatability of the method was determined at a flumetralin concentration level equal to 5.0 × 10−9 mol dm−3 and expressed as %RSD = 5.0% (n = 6). The proposed method was applied and validated successfully by studying the recovery of herbicide content in spiked environmental samples.Graphical abstract

Voltammetric behavior and determination of the macrolide antibiotics azithromycin, clarithromycin and roxithromycin at a renewable silver – amalgam film electrode

The renewable silver-amalgam film electrode (Hg(Ag)FE) was applied for voltammetric characterization and determination of semi-synthetic macrolide antibiotics azithromycin (AZI), clarithromycin (CLA) and roxithromycin (ROX) in the Britton-Robinson buffer as supporting electrolyte ranging the pH from 4.0 to 11.9. All three macrolides showed reduction signals in fairly negative potential range.During direct cathodic square wave voltammetric (SWV) investigations conducted over the potential range from −0.75V to −2.00V vs SCE, either one or two reduction peaks were obtained in the potential range from −1.5 to −1.9V. The shapes and intensities of the signals depend on the applied pH values in wider pH ranges. For analytical purposes concerning the development of direct cathodic SWV and adsorptive stripping SWV (SW-AdSV) methods the neutral and slightly alkaline media were suitable as pH 7.2, pH 7.4 and pH 7.0 for AZI, CLA and ROX, respectively. Based on the cyclic voltammograms recorded at these pH values, adsorption-controlled electrode kinetics process can be proposed for all three macrolides. Furthermore, the water suppressed 1H NMR measurements in the pH range between 6.0 and 10.5 indicated that the macrolide molecules at the optimal analytical conditions are predominantly in protonated form via their tertiary amino groups which supported in all three cases their adsorption on the appropriately polarized Hg(Ag)FE electrode. The optimized direct cathodic SWV methods showed good linearity in concentration ranges 4.81–23.3μgmL−1, 1.96–28.6μgmL−1 and 1.48–25.9μgmL−1 for AZI, CLA and ROX, respectively. The development of the SW-AdSV methods resulted in the linear responses at lower concentration ranges as 1.0–2.46μgmL−1, 0.05–0.99μgmL−1 and 0.10–0.99μgmL−1, for AZI, CLA and ROX, respectively. The relative standard deviation for all developed methods was not higher than 1.0% except the SWV method for AZI with 4.7%. In the case of all three investigated macrolide antibiotics the protonated form of the tertiary amino group(s) at appropriate accumulation potential and time favored the adsorption of the ionic form of the target molecules offering the opportunity for the development of SW-AdSV methods for their trace level analysis on Hg(Ag)FE. Optimized SW-AdSV method was applied for determination of ROX in pharmaceutical preparation Runac®.

Comparative Study on Electroanalysis of Fenthion Using Silver Amalgam Film Electrode and Glassy Carbon Electrode Modified with Reduced Graphene Oxide

AbstractOxidation and reduction processes of the insecticide fenthion was comparatively investigated at a reduced graphene oxide modified glassy carbon electrode (RGO‐GCE) and a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) using square wave stripping voltammetry (SWSV). The influence of pH and SW parameters was investigated. The linear concentration ranges were found to be 1 × 10−6 – 2 × 10−5 and 1 × 10−7 – 2 × 10−5 mol L−1 for Hg(Ag)FE and RGO‐GCE, respectively. The detection and quantification limits were calculated as 1.3 × 10−7 and 4.5 × 10−7 mol L−1 for Hg(Ag)FE and 7.6 × 10−9 and 2.5 × 10−8 mol L−1 for RGO‐GCE. Both of the developed electroanalytical methods offer rapid and simple detection of fenthion and were used on spiked tap and river water and apple juice samples. Scanning electron microscopy was used for RGO‐GCE surface characterization.

Voltammetric analysis of disulfiram in pharmaceuticals with a cyclic renewable silver amalgam film electrode

Electrochemical properties of disulfiram, representative of highly significant bioactive compounds, were studied with a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) using square wave cathodic stripping voltammetry (SWCSV). The influence of various factors such as pH, buffer concentration, buffer composition, and SWCSV parameters on current response was investigated. The optimum results in terms of signal shape and intensity were recorded in Britton--Robinson buffer (pH 7.5) at -0.5 V versus Ag/AgCl/3 mol L$^{-1}$ KCl. An elaborated electroanalytical procedure was used to determine disulfiram at the Hg(Ag)FE in the concentration range from 0.05 to 5.00 $\mu $M. Precision, repeatability, and accuracy of the method as well as the influence of possible interferences were ascertained. The detection and quantification limits were 11 nM and 37 nM, respectively. The applicability of the developed method was tested in the determination of disulfiram in the commercial formulation Anticol. Thin-layer chromatography with image processing software was used to validate the accuracy of the method.

Nanomaterials vs Amalgam in Electroanalysis: Comparative Electrochemical Studies of Lamotrigine

This paper reports a comparative study of electrochemical oxidation and reduction of lamotrigine (LMT) at a modified glassy carbon electrode (MWCNT/RGO–GCE) and a cyclic renewable silver amalgam film electrode (Hg(Ag)FE). Therefore, square wave voltammetry was employed to enable comparison of electrode mechanisms and analytical responses by analysis of voltammetric signals. The analytical performance of both electrodes, including quantification and detection limits, recovery, and reproducibility, was evaluated. The prepared sensors showed good sensitivity and selectivity for LMT determination in pharmaceutical formulations and urine samples. The results indicated that both of the tested electrodes and the developed methods can be considered as suitable tools and interesting alternatives in terms of analytical determination of lamotrigine. It was also stated that the recorded reduction signal is a consequence of two-electron process involving reduction of the azo group, while the oxidation peak is attributed to grafting and further dimerization of LMT molecules. AFM microscopy was used to characterize the modified electrode structure.

Voltammetric and corrosion studies of the ionophoric antibiotic–salinomycin and its determination in a soil extract

Salinomycin monosodium salt (SLM) is a widely used ionophoric antibiotic with a broad spectrum of activity. In this paper, a study is reported on the first electrochemical investigation of SLM. The use of square wave voltammetry (SWV) in combination with a renewable silver amalgam film electrode (Hg(Ag)FE) is presented for the determination of SLM in a spiked soil extract. A reduction peak at −1.40V vs. an Ag/AgCl/KCl reference electrode was obtained in Britton–Robinson (B–R) buffer (pH7.0). The influences of conditioning potential and time, frequency, amplitude, step potential and equilibration time were studied. This electroanalytical procedure was used to determine SLM on an Hg(Ag)F electrode at a concentration range of 2.5×10−7–2.5×10−6molL−1. The precision and repeatability of the method were checked. The limit of detection and quantification were 7.8×10−8molL−1 and 2.5×10−7molL−1, respectively. To understand the SLM electrode mechanism, the cyclic voltammetry (CV) technique was applied. Moreover, the effect of SLM on the corrosion properties of stainless steels used to produce metal bowls and feed troughs was studied using the potentiodynamic method.

Electrochemical determination of closantel in the commercial formulation by square-wave adsorptive stripping voltammetry

In this paper, the square-wave adsorptive stripping voltammetric (SWAdSV) determination of the veterinary drug closantel using a renewable silver amalgam film electrode (Hg(Ag)FE) is presented. As observed in SWAdSV, closantel provided one well-shaped reduction peak suitable for analytical purposes at potential ca. −1.4 V in the Britton–Robinson (B-R) buffer at pH 7.0. At optimal conditions, the SWAdSV response of Hg(Ag)FE for determining closantel was linear over two concentration ranges of 5.0 × 10−8 to 2.0 × 10−7 mol dm−3 and 2.0 × 10−7 to 1.2 × 10−6 mol dm−3 with a detection limit of 1.1 × 10−8 mol dm−3. In addition, a relevance of the developed SWAdSV method was successfully verified by the quantitative analysis of closantel in the commercial formulation Closamectin Pour-On with satisfactory results (RSD = 5.8%, recovery = 101.8%). The results showed that the developed procedure can be adequate for screening purposes. Also, the electrochemical behavior of closantel was characterized by cyclic voltammetry, and it was found that closantel exhibited a quasi-reversible behavior with cathodic peak on the forward scan at ca. −1.4 V and anodic peak on the reverse scan at ca. −1.35 V vs. Ag/AgCl in B–R buffer, pH 7.0. As the obtained results showed that the electrode mechanism of closantel is controlled by the adsorption, the effect of adsorption was studied using the electrochemical impedance spectroscopy technique.Graphical abstract

New sensitive square-wave adsorptive stripping voltammetric determination of pesticide chlornitrofen, and an evaluation of its corrosivity towards steel agricultural equipment

The electrochemical reduction of a fungicide, chlornitrofen (Cnf), was carried out on a renewable silver amalgam film electrode (Hg(Ag)FE). A new and sensitive square-wave adsorptive stripping voltammetric (SWAdSV) method of its determination was developed. The cathodic signal of Cnf at about −0.6V vs. Ag/AgCl/KCl was investigated in Britton–Robinson (B–R) buffer, pH8.8. Under optimized conditions, a linear calibration curve in the concentration range from 1.0×10−7molL−1 to 1.5×10−6molL−1 was obtained. The proposed SWAdSV method exhibited acceptable analytical performance in terms of the detection limit (LOD=3.0×10−8molL−1). The satisfactory repeatability of the voltammetric response for the different concentrations of Cnf was obtained (RSD=1.1%÷6.6%). Additionally, the practical applicability of the method was verified by the quantitative analysis of micromolar concentrations of Cnf in Warta River water samples. The corrosivity of pesticide Cnf towards stainless steel was tested using electrochemical techniques.

Rapid and Sensitive Voltammetric Determination of Aclonifen in Water Samples.

This paper presents the use of square wave voltammetry (SWV) and square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) for the determination of aclonifen in spiked water samples. A reduction peak at -0.65 V versus Ag/AgCl was obtained in the selected buffer (borax buffer with pH 9.2), exhibiting the characteristics of an irreversible reaction. The effect of square wave (SW) frequency, SW amplitude and step potential, as well as accumulation parameters (time and potential) were studied to select the optimal experimental conditions. The calibration curve was linear in the aclonifen concentration range from 1.0×10(-7) to 1.0×10(-6) mol L(-1) and from 1.0×10(-8) to1.0×10(-7) mol L(-1) for SWV and SWAdSV, respectively. The detection and quantification limits were found to be 3.1×10(-8) mol L(-1); 1.0×10(-7) mol L(-1) and 2.9×10(-9) mol L(-1); 9.6×10(-9) mol L-1 for SWV and SWAdSV, respectively. The proposed method was applied successfully in the determination of aclonifen in spiked water samples. The developed procedure can be adequate at least for screening purposes, where positive results should be confirmed by more selective method.

Voltammetric behavior of erythromycin ethylsuccinate at a renewable silver-amalgam film electrode and its determination in urine and in a pharmaceutical preparation

Erythromycin, a macrolide antibiotic, has similar antimicrobial spectrum to penicillin and it is widely used, especially in the treatment of patients who are allergic to penicillin.In this work, the application of a renewable silver-amalgam film electrode (Hg(Ag)FE) for the characterization and determination of erythromycin ethylsuccinate (EES), a widely used esterified form of this antibiotic, by means of cyclic voltammetry (CV) and square wave voltammetry (SWV) is presented. In the aqueous Britton-Robinson buffer (pH 5.0–9.0) that served as the supporting electrolyte, one reduction peak of EES was observed in the investigated potential range between −0.75V and −1.80V vs SCE, with peak potential maxima ranging from −1.59V to −1.70V, which strongly depended on the applied pH, as did the peak shape. For the analytical purposes the pH of 7.0 was selected, since in this electrolyte the EES peak was well-shaped and separated from the background current of the supporting electrolyte in both cases; in the direct cathodic SWV and in the case of square wave adsorptive stripping voltammetry (SW-AdSV). It was established, by the Ep-pH correlation, that protons strongly influenced the electrochemical reduction of EES. The CVs recorded between 0.025–0.50Vs−1 at pH 7.0 confirmed that the electrode reaction is adsorption-controlled. Based on the series of 1H NMR measurements it is proved that the tertiary amino group of EES is mainly in its protonated form at pH 7.0 which may lead, at appropriate accumulation potential and time, to the favored adsorption of the target ionic form of the analyte improving on such way the sensitivity of the SW-AdSV method.The optimized procedures resulted in stable SWV responses with good linear correlation in the EES concentration range from 4.53 to 29.8μgmL−1 (LOD=1.36μgmL−1), and from 0.69μgmL−1 to 2.44μgmL−1 (LOD 0.21μgmL−1) in the case of optimized SW-AdSV. The relative standard deviation is below 1.5%. The reliability of the elaborated procedures and thus the accuracy of the obtained results were validated by comparing them with those obtained by means of HPLC-DAD measurements. The direct cathodic SWV method was successfully applied for the determination of EES in the pharmaceutical preparation Eritromicin®, while SW-AdSV was applied in the case of the spiked urine sample. In both cases, the standard addition method was used.

Voltammetric and corrosion studies of the fungicide fludioxonil

A new, simple, rapid, and inexpensive voltammetric method for the determination of a novel fungicide, fludioxonil (Flu), was firstly developed using square wave voltammetry (SWV). This was based on its electrochemical cathodic reduction at about -1.1V vs. an Ag/AgCl/KCl reference electrode in citrate–phosphate (C–P) buffer (pH 3.7) on a renewable silver amalgam film electrode (Hg(Ag)FE). To select the optimum experimental conditions, the effect of the supporting electrolyte, pH, conditioning potential and conditioning time, frequency, amplitude, step potential, and equilibration time were studied. Under optimized conditions, the proposed method exhibited acceptable analytical performances in terms of linearity (over a concentration range from 2.00×10−6 to 2.25×10−5molL−1), the detection limit (LOD=5.81×10−7molL−1) and the quantification limit (LOQ=1.94×10−6molL−1) for a solution containing Flu. The validation of the method was carried out. The developed procedure was successfully applied to determine Flu in the spiked Warta River water samples. To understand the Flu electrode mechanism, the cyclic voltammetry (CV) technique was applied. The reduction mechanism was also confirmed using mass spectrometry with the electrospray ionization (ESI–MS) technique. The influence of Flu on the corrosion properties of stainless steels used to produce agricultural tools were investigated using electrochemical techniques.

Ultra trace level determination of fenoxanil by highly sensitive square wave adsorptive stripping voltammetry in real samples with a renewable silver amalgam film electrode

A new, simple, and highly sensitive voltammetric method for the determination of low concentrations of a novel fungicide, fenoxanil (Fen), was developed using square wave voltammetry (SWV) and square wave adsorptive stripping voltammetry (SWAdSV) on a renewable silver amalgam film electrode (Hg(Ag)FE). The electrochemical reduction of Fen at the Hg(Ag)FE in Britton-Robinson (B-R) buffer at pH 6.8 was studied for the first time. The effect of the supporting electrolyte, pH, conditioning potential and conditioning time, frequency, amplitude, step potential, and accumulation potential and accumulation time were studied to select the optimum experimental conditions. The developed method can determine Fen in the concentration range of 5×10−7–4×10−6molL−1 for SWV and 1×10−10–9×10−10molL−1 for SWAdSV. Validation of the method was carried out. The method was successfully applied for trace level determination of Fen in spiked Warta River water and spiked rice samples by the standard addition method. The interference of common agents and metal ions was also examined. Fen adsorption at the mercury electrode was studied.