Square-wave Adsorptive Stripping Voltammetric Research Articles

Voltammetric determination of organic UV filters by carbon paste electrodes modified with pyridinium-based ionic liquids

The rapid and sensitive voltammetric determination of organic UV filters benzophenone-3 (BP-3) and avobenzone (AVO) was performed by an ionic liquid carbon paste electrode (IL-CPE). Namely, the synthesized pyridinium-based ILs, 1-butyl-3-methylpyridinium chloride ([N–C4–3C1Py]Cl) and 1-ethoxyethyl-3-methylpyridinium chloride ([N–C2OC2–3C1Py]Cl) were compared as bulk CPE modifiers for BP-3 determination. [N–C4–3C1Py]Cl-CPE showed more favorable interactions with the target analyte, and it was tested for AVO determination, too. Cyclic voltammetric (CV) studies suggested that the irreversible electrode reaction is adsorption controlled in the case of both UV filters. Also, the square-wave adsorptive stripping voltammetric (SW-AdSV) method was optimized for quantifying selected UV filters. In the model solutions, the linear calibration curve was obtained by the SW-AdSV method in the concentration range from 0.05 to 0.89 μg mL−1 at pH 3.0 for BP-3 (Eacc = −0.7 V, tacc = 100 s), and from 0.05 to 1.77 μg mL−1 at pH 11.98 for AVO (Eacc = 0.2 V, tacc = 100 s). The evaluated limit of detection (LOD) was 0.015 μg mL−1 in both cases, while the relative standard deviation (RSD) was lower than 1.5%. The affordable IL-based voltammetric sensor fulfills the main requirements for application in real samples due to an adequate selectivity towards selected analytes in the presence of interferents usually found in swimming pool water. Therefore, the BP-3 and AVO were quantified in a swimming pool water matrix with good repeatability and recovery. The obtained results demonstrate an excellent potential of the IL-CPEs, especially of the [N–C4–3C1Py]Cl-CPE, for determining selected UV filters in various real samples.

Tetrabutylammonium Chloride Modified Carbon Paste Electrode for Rapid and Highly Sensitive Voltammetric Determination of Carbendazim

The voltammetric characterization and determination of fungicide carbendazim (methyl-1H-benzimidazol-2-yl-carbamate, CBZ) were performed using simple and highly sensitive electrochemical sensor based on tetrabutylammonium chloride (TBACl) ionic liquid as modifier of carbon paste electrode (CPE) and compared to conventional CPE in aqueous Britton-Robinson buffer solution as supporting electrolyte (pH 2.0–11.98). Cyclic voltammetric (CV) studies suggested that electrode reaction is mixed diffusion-adsorption controlled. Also, the square wave voltammetric (SWV) and square-wave adsorptive stripping voltammetric (SW-AdSV) methods were optimized for quantitation of CBZ. In the model solutions of pH 5.0, the linear calibration curves were obtained in CBZ concentration ranges from 2.5 to 280.0 ng ml−1 by SWV and from 1.5 to 40.0 ng ml−1 by SW-AdSV method (Eacc = −0.25 V, tacc = 180 s) with relative standard deviation lower than 2.0%. A great improvement in terms of CBZ electrochemical oxidation with low detection limit as 0.45 ng ml−1 was achieved using proposed highly sensitive SW-AdSV method. TBACl-CPE in combination with the optimized SWV and SW-AdSV methods was successfully applied for trace level determination of CBZ in spiked fruit juice and river water samples, respectively, with good recovery and reproducibility, demonstrating the reliability and accuracy of the developed methods.

Sensitive and selective determination of Cu2+ at d-penicillamine functionalized nano-cellulose modified pencil graphite electrode

A novel electrochemical sensor based on d-penicillamine anchored nano-cellulose (DPA-NC) modified pencil graphite electrode was fabricated and used for highly selective and sensitive determination of copper (II) ions in the picomolar concentration by square wave adsorptive stripping voltammetric (SWV) method. The modified electrode showed better and increased SWV response compared to the bare and NC modified electrodes which may be related to the porous structure of modifier along with formation of complex between Cu2+ ions and nitrogen or oxygen containing groups in DPA-NC. Optimization of various experimental parameters influence the performance of the sensor, were investigated. Under optimized condition, DPA-NC modified electrode was used for the analysis of Cu2+ in the concentration range from 0.2 to 50 pM, and a lower detection limit of 0.048 pM with good stability, repeatability, and selectivity. Finally, the practical applicability of DPA-NC-PGE was confirmed via measuring trace amount of Cu (II) in tap and river water samples.

β–Cyclodextrins incorporated multi-walled carbon nanotubes modified electrode for the voltammetric determination of the pesticide dichlorophen

In this work, a glassy carbon electrode modified with β–cyclodextrins and multi–walled carbon nanotubes (β–CDs/MWCNTs/GCE) was constructed and applied for the square-wave adsorptive stripping voltammetric (SWAdSV) determination of the pesticide dichlorophen (Dcp). For the first time, this compound was electrochemically investigated. The voltammetric measurements were conducted in phosphate buffer (PBS) at pH 6.5 as a supporting electrolyte, and SWAdSV technique parameters were optimized. A linear calibration curve in the wide concentration range from 5.0 × 10−8molL−1 to 2.9 × 10−6molL−1 was obtained. Excellent analytical performance in terms of limit of detection (LOD) of 1.4 × 10−8molL−1 was achieved. The utility of the proposed method was verified by the quantitative analysis of Dcp in Pilica River water samples with satisfactory results. The characterization of modified electrodes was conducted by means of atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Moreover, in this work, the dissociation constants (pKa) of Dcp using potentiometric pH titration were estimated. The stoichiometry of the Dcp–β–CDs inclusion complex formed in solution was determined by proton nuclear magnetic resonance (1H NMR) spectroscopy, and a binding constant (β2) was estimated from NMR titration studies.

Adsorptive Stripping Voltammetric Determination of Trace Level Ricin in Castor Seeds Using a Boron‐doped Diamond Electrode

AbstractRicin, (Ricinus communis agglutinin, RCA) is one of the most poisonous of naturally occurring substances and has great potential for bioterrorism because no antidote exists. Fast detection at low concentrations is a challenge, and vital to the development of proper countermeasures. In this study, a square wave adsorptive stripping voltammetric (SWAdSV) method for determining RCA using a cathodically polarized boron‐doped diamond (BDD) electrode is presented. An irreversible electrochemical RCA oxidation peak was identified on the BDD electrode by different voltammetric techniques using both direct and adsorptive stripping modes. An adsorption‐controlled (slope log Ip vs log v of 0.80) pH‐dependent process was observed. For values of 1.0≤pH≤9.0, the numbers of protons and electrons associated with the oxidation reaction were estimated (ca. 1.0) by differential pulse voltammetry. The RCA oxidation step may correspond to the oxidation of tryptophan amino acid residues, and occurs in a complex mechanism. The excellent analytical performance of the cathodically polarized BDD electrode in combination with the stripping mode ramp was verified with RCA by using a short deposition time in an open circuit potential (120 s). Under optimized analysis conditions, a linear response in the range of (3.3–94.0)×10−9 mol L−1 (r2=0.9944) and a limit of detection of 6.2×10−10 mol L−1 were estimated. This LOD is lower than several methods found in the literature. For example, it is 168 times lower than that obtained by using square wave voltammetric with a glassy carbon electrode. Moreover, an even lower LOD might be achieved by using the SWAdSV method with a higher pre‐concentration time. In addition, trace levels of RCA were successfully determined in different castor seed cultivars with an overall average recovery from 99.2±1.6 % for the three different RCA‐A concentration levels. The high accuracy of the analytical data highlights the use of the proposed method for determining RCA in other samples.

A New and Cost Effective Approach for Simultaneous Voltammetric Analysis of two Related Benzimidazole Drugs and their Determination in Biological Fluids

AbstractA polymerized film of eriochrome black T (EBT) was prepared on the surface of pencil graphite electrode in alkaline solution by cyclic voltammetry. The redox response of the poly (EBT) film at the electrode appeared in a couple of redox peak in 0.1 M sodium hydroxide. The poly (EBT) film‐coated electrode exhibited excellent electrocatalytic activity towards the oxidation of rabeprazole sodium (RAB sodium) and domperidone (DOM) in Britton‐Robinson buffer (pH 4.0). The polymer film modified electrode conspicuously enhanced the redox currents of the cited mixture and could sensitively and separately determine them. Both cyclic voltammetry (CV) and square wave adsorptive stripping voltammetric (SWAdSV) methods were utilized to determine this mixture. The linearity of CV ranged from 4.1‐120 μM and 5.2‐90 μM for RAB sodium and DOM, respectively while SWAdSV was 7.5‐80×10−7M and 5–70×10−7M for RAB sodium and DOM, respectively. With good selectivity and sensitivity, the present method provides a simple method for selective detection of RAB sodium and DOM binary mixture in synthetic mixtures and biological fluids.

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.

TiO2 modified carbon paste sensor for voltammetric analysis and chemometric optimization approach of amlodipine in commercial formulation

A new square wave adsorptive stripping voltammetric (SWAdSV) approach using experimental design and optimization methodology was developed for the quantitative estimation of amlodipine (AMP) in pharmaceutical tablets. To this end, a new carbon paste electrode (CPE) system was fabricated using titanium dioxide (TiO2) nanoparticles to get very well-defined oxidation peak current of AMP under the optimized conditions. Optimal electrochemical conditions for three factor variables, the pH, the accumulation potential, and the accumulation time, were obtained by applying a 33 full factorial design and optimization technique to the oxidation of AMP on the TiO2 modified CPE (TiO2-CPE) system. The numerical values of the optimal voltammetric parameters consisting of the pH, accumulation potential, and accumulation time were found to be 5.69, 562.30 mV, and 64.30 s for the analysis of AMP in samples, respectively. The newly developed voltammetric method for the determination of AMP offers a linear relationship between the peak current and concentration in the range of 1.0 × 10−8 − 1.0 × 10−6 M with the correlation coefficient (r = 0.9990) and the detection limit (LOD = 2.97 × 10−9 M). The lifetime of prepared electrode was also tested, and the current intensity of AMP was nearly stable at least 2 months by using TiO2-CPE. The validity of the method was tested by analyzing standard samples containing the analyzed compound. Under optimized and validated experimental conditions, the proposed method was successfully applied for the quantitative analysis of AMP in commercial tablets.

Electroanalytical determination of heavy metals in drinking waters in the eastern province of Saudi Arabia

The direct and simultaneous determination of lead(II), cadmium(II), and zinc(II) heavy metals in drinking water was carried out using the square wave adsorptive stripping voltammetric (SWASV) technique at different Bi-modified carbon electrode surfaces, including glassy carbon, carbon paste, and graphite pencil. Among the various trace metal technologies, electrochemical stripping analysis is most likely to meet the requirements of on-site metal analysis. In the absence or presence of 600 ppb Bi(III) in an acetate buffer solution (0.1 M, pH 3.5), the metal ions were deposited by reduction at –1.4 V (vs. Ag/AgCl Sat. KCl) onto the carbon electrode surfaces. The deposited metals were oxidized by scanning the potential of the electrode surface from –1.5 to 0.0 V using the SWASV measurements. The stripping currents arising from the oxidation of the corresponding metals were correlated to the concentration of the metals in the water sample. The analytical utility of the bismuth-coated sensors developed here depended on an understanding of their fundamental properties. The obtained results enable heavy metal detection at low (ppb) detection limits, significantly impact the monitoring of inorganic contaminants in drinking water, and improve our management of drinking water supplies.

The new application of renewable silver amalgam film electrode for the electrochemical reduction of nitrile, cyazofamid, and its voltammetric determination in the real samples and in a commercial formulation

Until recently cyanides were considered to be electrochemically non-reducible in aqueous solutions at mercury electrodes, but reducible at nickel, copper and silver electrodes. In our studies we noticed that the process is going on also at a renewable silver amalgam film electrode (Hg(Ag)FE). The electrochemical reduction of a novel fungicide with nitrile group, cyazofamid (Cfd) at the Hg(Ag)FE was studied for the first time. A rapid, sensitive, and new square-wave adsorptive stripping voltammetric (SWAdSV) method using a Hg(Ag)FE has been developed for the determination of Cfd. In order to understand the Cfd electrode mechanism, CV and SWAdSV techniques were applied. Cfd reduces at the Hg(Ag)FE with the cathodic signals being dependent on pH. The signal obtained at about -1.10V (citrate-phosphate (C-F) buffer, pH 2.6) was used for analytical purposes. Various parameters of the procedure, such as: pH, conditioning potential and time, frequency, amplitude, step potential, accumulation potential and time, were investigated. The developed SWAdSV method enabled Cfd determination in the concentration range of 4.00×10−6-2.00×10−5molL−1. The procedure was successfully validated. The standard addition method was applied to determine Cfd in spiked Danube water and potato samples, and in the commercial formulation RANMAN Top. The effect of common interfering pesticides and heavy metal ions was also investigated. The adsorption of Cfd at the mercury electrode was studied.

Conditioning of renewable silver amalgam film electrode for the characterization of clothianidin and its determination in selected samples by adsorptive square-wave voltammetry

A new square-wave adsorptive stripping voltammetric (SWAdSV) method was developed for the determination of the neonicotinoid insecticide clothianidin (Clo), based on its reduction at a renewable silver amalgam film electrode (Hg(Ag)FE). The key point of the procedure is the pretreatment of the Hg(Ag)FE by applying the appropriate conditioning potential (-1.70 V vs. Ag/AgCl reference electrode). Under the optimized voltammetric conditions, such pretreatment resulted in the peak for the Clo reduction in Britton-Robinson buffer pH 9.0 at about -0.60 V, which was used for the analytical purpose. The developed SWAdSV procedure made it possible to determine Clo in the concentration range of 6.0×10(-7)-7.0×10(-6) mol L(-1) (LOD=1.8×10(-7) mol L(-1), LOQ=6.0×10(-7) mol L(-1)) and 7.0×10(-6)-4.0×10(-5) mol L(-1) (LOD=1.3×10(-6) mol L(-1), LOQ=4.2×10(-6) mol L(-1)). The repeatability, precision, and the recovery of the method were determined. The effect of common interfering pesticides was also investigated. Standard addition method was successfully applied and validated for the determination of Clo in spiked Warta River water, corn seeds samples, and in corn seeds samples treated with the commercial formulation PONCHO 600 FS.

Square-wave adsorptive stripping voltammetric determination of antihypertensive agent telmisartan in tablets and its application to human plasma

The adsorptive stripping voltammetry of telmisartan was investigated with a hanging mercury drop electrode. This compound produced a catalytic hydrogen wave at -1.5 V in Britton Robinson buffer of pH 10.38, and the peak current increased with adsorptive accumulation at the electrode. Adsorptive stripping voltammetry with the catalytic hydrogen wave could provide a sensitive novel method for the determination of telmisartan. Various chemical and instrumental parameters affecting the monitored electroanalytical response were investigated and optimized for telmisartan determination. Under these optimized conditions the squarewave adsorptive stripping voltammetric ( SWAdSV ) peak current showed a linear dependence on drug concentration over the range 0.05-3.00 µg/mL (1 × 10 -7 ⎯6 × 10 -6 M) (r = 0.999) with accumulation for 120 s at -1.0 V vs. Ag/AgCl. The proposed electrochemical procedure was successfully applied for the determination of telmisartan in pharmaceutical tablets and human plasma. The results of the developed SW� AdSV method were comparable with those obtained by reported analytical procedures.

Determination of gemfibrozil in pharmaceutical and urine samples by square-wave adsorptive stripping voltammetry using a glassy carbon electrode modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film

Glassy carbon electrode modified with functionalized multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film was used to develop a sensitive and simple square-wave adsorptive stripping voltammetric (SWAdSV) method for the determination of gemfibrozil. The cyclic voltammograms obtained showed one irreversible anodic peak for gemfibrozil at a potential of 1.3V using a 0.1molL−1 phosphate buffer solution (pH2.0). The cyclic voltammetric responses were studied with regard to scan rate, and the number of electrons transferred during the oxidation process was calculated. A calibration curve for gemfibrozil in the concentration range from 75 to 1000nmolL−1 with a detection limit of 53nmolL−1 were obtained. The proposed SWAdSV method was successfully applied to determine gemfibrozil in pharmaceutical and urine samples with good accuracy and precision.

An electroanalytical study of the drug proflavine

A square wave adsorptive stripping voltammetric (SWAdSV) method was developed for the determination of proflavine. The electrochemical behaviour of proflavine was investigated by cyclic (CV) and square wave voltammetry (SWV) at the hanging mercury drop electrode (HMDE) and carbon paste electrode (CPE). Different parameters were tested to optimize the conditions of the determination. Better results were obtained by square wave voltammetry using CPE where two oxidation and a reduction peak, appeared, at 0.19, 0.94 and 0.20 V, respectively. The peak at 0.19 V is quasi-reversible and deposition dependent. Linearity was observed in the range of (0.2–23.4) × 10−8 M (r = 0.998) during the anodic scan and in the range of (1.17–117) × 10−8 M (r = 0.999) during the cathodic scan. The second peak at 0.94 V is irreversible and deposition independent. The linearity of this peak was observed in the range of (1.29–11.7) × 10−8 M (r = 0.998). The method was applied to the analysis of bovine serum and gave satisfactory results.

Voltammetric quantitation at the mercury electrode of the anticholinergic drug flavoxate hydrochloride in bulk and in a pharmaceutical formulation

Abstract Flavoxate hydrochloride, 2-piperidinoethyl 3-methyl-4-oxo-2-phenyl-4-H-chromene-8-carboxylate, is a smooth muscle antispasmodic. Its electrochemical behavior was studied at the mercury electrode in buffered solutions containing 30% (v/v) methanol using dc-polarography, differential-pulse polarography, cyclic voltammetry, and linear sweep-and square-wave adsorptive stripping voltammetry. Sensitive and precise procedures were developed for determination of bulk flavoxate hydrochloride and in the pharmaceutical formulation Genurin® S.F, without sample pretreatment or extraction. Limits of quantitation (LOQ) of 1 × 10−5, 5 × 10−6, 1 × 10−8 and 1 × 10−9 M flavoxate hydrochloride were achieved by dc-polarography, differential-pulse polarography, linear sweep and square-wave adsorptive stripping voltammetric, respectively.

Square-wave adsorptive stripping voltammetric determination of danazol in capsules

Based on the interfacial adsorptive character of danazol onto the hanging mercury drop electrode (HMDE), a simple and sensitive square-wave adsorptive stripping voltammetric (SW-AdSV) procedure for the electrochemical analysis of this drug in pharmaceutical formulations has been developed and validated. Cyclic and SW-AdSV voltammograms showed a single well-defined irreversible cathodic peak. Various chemical and instrumental parameters affecting the monitored electroanalytical response were investigated and optimized for the danazol determination. Under these optimized conditions the SW-AdSV peak current showed a linear dependence on drug concentration over the range 7.5x10(-8)-3.75x10(-7) mol l-1 (r=0.999) with estimated detection limit (at a S/N ratio of 3) of 5.7x10(-9) mol l-1 (1.78 ng ml-1). A mean recovery of 100.9+/-1.2% and relative standard deviation of 1.07% were achieved. Possible interferences by substances usually present in the pharmaceutical tablets and formulations were also evaluated. The proposed electrochemical procedure was successfully applied for the determination of danazol in pharmaceutical capsules (Danol 100 mg) with mean recoveries of 100.48+/-0.87%. Results of the developed SW-AdSV method were comparable with those obtained by reported analytical procedures.

A novel method for determination of magnesium in urine and water samples with mercury film-plated carbon paste electrode

A square wave adsorptive stripping voltammetric (SWAdSV) method for the indirect determination of trace amounts of magnesium with thiopentone sodium (TPS) as an electroactive ligand, at carbon paste mercury film electrode (CP-MFE) is proposed. It is observed that the increase of the square wave voltammetric cathodic peak current of TPS, under alkaline conditions, is linear with the increase of Mg concentration. Under optimum experimental conditions viz.; pH 10.75, 3×10−5M TPS and 0.05M phosphate buffer (Na2HPO4–NaH2PO4), a linear relation in the range 6×10−9 to 9×10−8M Mg2+ (0.14–2.16ppb), at 60s deposition time, is obtained. The detection limit of Mg2+ is 0.14ppb for 60s deposition time with the relative standard deviation is 0.5% (n=5). The proposed method was successfully applied to the determination of magnesium in urine and tap water samples with satisfactory results. The data obtained are compared with the standard flame atomic absorption spectrophotometric method (FAAS).