Pulse Voltammetric Techniques Research Articles

RECENT ADVANCES AND PROSPECTS OF SQUARE-WAVE VOLTAMMETRY

This review concerns recent methodological advances of square-wave voltammetry as one of the most sophisticatedmembers of the pulse voltammetric techniques. Besides addressing recent theoretical works and representatives ofadvanced analytical studies, an emphasis is given to a few novel methodological concepts such as kinetic analysis atconstant scan rate, cyclic square-wave voltammetry, multisampling square-wave voltammetry, and electrochemical faradaicspectroscopy. For the purpose of improving analytical performances of the technique two new methods are proposedfor the first time.

A novel design and synthesis of ruthenium sulfide decorated activated graphite nanocomposite for the electrochemical determination of antipsychotic drug chlorpromazine

A novel electrochemical sensor based on ruthenium sulfide nanoparticles decorated activated graphite sheets (RuS2/AG) was designed and fabricated for the determination of antipsychotic drug chlorpromazine hydrochloride (CPZ). Activated graphite sheets (AG) were prepared by non-explosive, non-hazardous and simple chemical activation technique. Then, the AG sheets were used for the synthesis of RuS2/AG nanocomposite by single step hydrothermal synthesis method. The synthesized materials were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), Raman spectrometer, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The synergistic effect of the RuS2/AG nanocomposite was applied for the determination of CPZ by cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques. Fascinatingly, the RuS2/AG nanocomposite exhibited the excellent electrocatalytic activity and detects the CPZ at very lowest oxidation potential about 0.60 V vs Ag/AgCl in pH-7 PB solution. Moreover, the lowest LOD 8 nM and wider linear ranges from 0.05 to 79.75 and 79.75–1249 μM was obtained towards the CPZ determination. Besides, the proposed sensor shows the good selectivity, satisfactory repeatability, reproducibility and stability. Furthermore, the real time application was evaluated in pharmaceutical tablets and human urine samples.

Theoretical Contribution towards Understanding Specific Behaviour of “Simple” Protein‐film Reactions in Square‐wave Voltammetry

AbstractSurface reactions of uniformly adsorbed redox molecules at working electrode surface are seen as adequate models to studying chemical reactivity of many lipophilic enzymes. When considered under pulse voltammetric techniques, these systems show several uncommon features, whose origin is still not completely clear. The phenomena of “quasireverible maximum”, “splitting” of the net peak in square‐wave voltammetry, and the very steep descent of Faradaic currents of simple surface redox reactions exhibiting fast electron transfer are just some of the features that make these systems quite interesting for further elaborations. In this work, we present a set of theoretical calculations under conditions of square‐wave voltammetry in order try to explain some of aforementioned phenomena. The major goal of our work is to get insight to some voltammetric and chrono‐amperometric features of two considered surface reactions, i. e. (1) the “simple” surface redox reaction, and (2) surface redox reaction coupled to follow‐up irreversible chemical reaction of electrochemically generated redox species (or surface ECirr). We focus on the role of created Red(ads) (here in the reduction pulses only) to the current components of calculated square‐wave voltammograms exhibiting fast electrode reaction. We show that the irreversible chemical removal of electrochemically generated Red(ads) species, created in the potential pulses where half‐reaction of reduction Ox(ads)+ne‐−→Red(ads) is “defined” to take place, causes significant increase of all square‐wave current components. The results presented in this work show how complex the chrono‐amperometric features of surface redox reactions under pulse voltammetric conditions might be. In addition, we point out that both half reactions of a given simple surface redox process can occur, at both, “only reduction” and “only oxidation” potential pulses in square‐wave voltammetry. This, in turn, contributes to the occurrence of many phenomena observed in simple protein‐film voltammetry reactions. The effects of chemical reaction rate to the features of calculated square‐wave voltammograms of surface ECirr systems with fast electrode reaction are reported for the first time in this work.

Square-wave voltammetry

This text is written as a very basic, first introduction to square-wave voltammetry, as one of the very specific, but most versatile techniques in the family of pulse voltammetric techniques. To make the text self-consistent, a brief introduction to voltammetry is initially given, to make the next elaboration of square-wave voltammetry more easily understandable. For more comprehensive introduction to voltammetric techniques, the previous chem-text is recommended (Scholz in ChemTexts 1:17, 2015). The aim of the current text is to explain the basic features of square-wave voltammetry, to reveal the essential idea behind the specific shape of the excitation signal used, as well as to demonstrate that square-wave voltammetry is highly suited to study the mechanism of electrode reactions. The latter is illustrated by addressing the simplest experimental situation encountered in voltammetry to make the text didactically suited for broader student population studying chemistry and related sciences.

Tailoring of nanostructured material as an electrochemical sensor and sorbent for toxic Cd(II) ions from various real samples

The aim of the present study is the fabrication of electrochemical sensor and sorbent for toxic Cd(II) ion using ion-imprinting technique on vinyl-functionalized multiwalled carbon nanotube. Multiwalled carbon nanotube-based ion-imprinted polymer (MWCNT-IIP) were synthesized using meth acrylic acid as the functional monomer, N,N′methylene-bis-acrylamide as the cross linking agent, and potassium peroxo disulphate as an initiator. The template and porogen used were cadmium chloride and water. To know the importance of MWCNT, ion-imprinted polymer without MWCNT was also prepared. For the purpose of comparison, non-imprinted polymers were also synthesized. The synthesized products were analyzed by FT-IR, XRD, TEM, EDAX, and TGA. An electrochemical sensor was made up by modifying platinum electrode with MWCNT-IIP. Experimental factors that control the routine of the sensor were investigated and optimized. Under optimal conditions, a calibration curve was obtained with a detection limit of 0.03 μM by using differential pulse voltammetric technique. Selectivity studies show irrelevant significance with Zn (II), Cu (II), and Ni (II) ions. The feasibility of modified platinum electrode shows a prospective application in real water sample collected from a lake, pigments, cosmetics, and fertilizers. The synthesized nanostructured material is also used for the extraction of Cd(II) ion from real water samples. The maximum adsorption of Cd(II) by various imprinted and non-imprinted sorbents was calculated, and it was found that maximum adsorption takes place at pH 6. The kinetic studies show that the adsorption of Cd(II) increases with time and reaches equilibrium at 70 min and the kinetic data follow pseudo-second-order kinetics. The adsorption data fitted to the Langmuir adsorption model which confirms the monolayer formation of an IIP layer on MWCNT surface. The selectivity co-efficient of the imprinted sorbent shows high selectivity and specificity towards Cd(II) ion than other metal ions.

Electrochemical Behavior of an Anti-Viral Drug Valacyclovir at Carbon Paste Electrode and Its Analytical Application

Valacyclovir (VCH) is an antiviral drug, used in the management of viral infections such as herpes simplex and varicella-zoster in humans. It is rapidly converted to acyclovir which has antiviral activity against herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) and Varicella-zoster virus (VZV) both in vitro and in vivo. Electrochemical behavior was studied using cyclic voltammetric method, and the analytical application was studied using differential pulse voltammetric technique. The process on the surface of electrode was found to be irreversible and diffusion controlled. The charge transfer coefficient, heterogeneous rate constant, the number of electron transferred and activation parameters were calculated. Possible free radical reaction mechanism taking place on the surface of electrode was proposed. Calibration plot constructed using differential pulse voltammetric technique and applied for quantitative analysis in pharmaceutical and human urine sample. Limit of detection (LOD) and limit of quantification (LOQ) were calculated and found to be 0.028 and 0.09 μM, respectively. The present work describes the electrochemical behavior of an antiviral drug, VCH and its determination in pharmaceutical samples. The method shows the development of a sensor for selective and sensitive determination of VCH.

Femtomolar Detection of Dengue Virus DNA with Serotype Identification Ability.

Dengue surveillance trusts only on reverse transcription-polymerase chain reaction (RT-PCR) type methodologies for confirmation of dengue virus serotypes; however, its real time application is restricted due to the expensive, complicated, and time-consuming process. In search of a new sensing system, here, we have reported a two-way-detection method for Dengue virus (DENV) serotype identification along with DNA quantification by using a new class of nanocomposite of gold nanoparticles (AuNP) and nitrogen, sulfur codoped graphene quantum dots (N,S-GQDs). The N,S-GQDs@AuNP has been used for serotype detection via a simple fluorescence technique using four dye-combined probe DNAs which is further validated by confocal microscopy. The quantification of the DNA has been measured by the differential pulse voltammetric (DPV) technique using methyelene blue as a redox indicator. Results obtained in this study, clearly demonstrate that the N,S-GQDs@AuNP can efficiently detect the four serotypes of DENV individually in the concentration range of 10-14 to 10-6 M with the LOD of 9.4 fM. In addition, to confirm its applicability in long chained complex DNA system, the sensor was also applied to the clinically isolated DENV DNA and showed satisfactory performances for serotype identification as well as quantification. We hope this simple and reliable method can pave an avenue for the development of sensitive and robust sensing probes in biomedical applications.

Development of an effective electrochemical platform for highly sensitive DNA detection using MoS2 - polyaniline nanocomposites

Molybdenum disulfide (MoS2) and its associated nanocomposites are widely explored in different applications like capacitance, batteries, sensing etc. However, the nanosheet formation of MoS2 exhibits excellent properties for DNA adsorption without any further surface or probe DNA modification which makes it a suitable matrix for the less explored DNA sensing application. In this present work, an ultrasensitive electrochemical DNA biosensor, based on few layered MoS2 nanosheets blended with conducting polymer, polyaniline is constructed as a sensing platform and used as a DNA sensing probe via differential pulse voltammetric technique. The sensor works well even at concentrations as low as 10−15 M of target DNA without labeling or any use of amplifiers. The sensing performances show highly satisfactory results in case of serum samples and in presence of other interferrants. In addition, the sensor can successfully recognize any positional mismatch in a known concentration of targeted DNA which can lead to a DNA mismatch senor in near future. The detection method described here expands the application of MoS2 in the biosensor field with a viable alternative for easy, cost effective electrochemical DNA detection technique with mismatch identification capability.

MWCNT/CdSe quantum dot modified glassy carbon electrode for the determination of clopidogrel bisulfate in tablet dosage form and serum samples

In this study, clopidogrel (CLP), which is an antiplatelet agent widely used in the prevention of ischemic stroke, was analyzed using functionalized multi-walled carbon nanotubes (fMWCNTs) and CdSe quantum dots (QDs) modified glassy carbon electrode. The dependence of intensities of currents and potential on pH, concentration, scan rate, nature of the buffer was further investigated. The oxidation process exhibited mixed diffusion under adsorption controlled process depending on pH. For the analytical application, adsorptive stripping differential pulse voltammetric (AdSDPV) technique was used and all operational parameters were optimized. The plot of peak current vs CLP concentration consisted of a linear segment in the concentration range between 2.0 × 10−6 M and 4.0 × 10−5 M and the detection limit (3σ) was obtained 7.55 × 10−8 M in pH 2.14 phosphate buffer solution. Moreover, in order to evaluate the analytical applicability of the proposed method, it was applied to the determination of CLP in serum samples with linear range of 2.5 × 10−6–1.5 × 10−5 M and the detection limit value of 2.99 × 10−7 M. Determination of CLP in tablet dosage form Atervix® was also proposed with acceptable recovery values.

Synthesis and characterization of nanostructured nickel phosphate as a robust electrocatalyst for the highly sensitive voltammetric determination of chlorpromazine in biological sample

Abstract The exploration of highly active and cost-effective catalysts for the electrochemical sensor is crucial to facilitate the improvement in detection techniques. In this study, we report a facile hydrothermal synthesis of nanostructured nickel phosphate (NiP) for the application towards the electrochemical determination of chlorpromazine (CPZ) in biological samples. The synthesized nanostructured NiP was characterized using powder X-ray diffraction, Fourier transforms infrared spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and elemental mapping techniques. The characterization results exhibit that the prepared electrocatalyst material showed rice bundle-like nanostructure. Furthermore, electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetric techniques were performed to analyze the electrochemical properties of the prepared nanocomposite. Remarkably, as-prepared rice bundle like NiP modified electrode delivers an excellent sensing performance for the detection of CPZ. The nanostructured NiP modified electrode showed the excellent linear range (0.008–34 µM; 36–221.4 µM), low-level detection limit (0.002 µM) and high sensitivity (8.526 µA/µM cm2), which is superior to that of all other electrocatalysts to sense CPZ. The most active nanostructured NiP modified electrode exhibited good selectivity towards CPZ, and the detection of CPZ in real sample (human urine) showed satisfactory recoveries. Thus, this facile and super active nanostructured NiP material proven to be a promising electrode material in electrochemical sensors.

Nanocarbon material-supported conducting poly(melamine) nanoparticle-modified screen-printed carbon electrodes for highly sensitive determination of nitrofuran drugs by adsorptive stripping voltammetry.

The toxicity of nitrofuran drugs has attracted great attention, and the reported electroanalytical methods suffered limited sensitivity. In this work, a sensitive electrochemical assay in the cathodic region is developed to determine four nitrofuran derivatives, including nitrofurantoin (NFT), nitrofurazone (NFZ), furaltadone (FTD), and furazolidone (FZD). The screen-printed carbon electrode (SPCE) was used as the electrode substrate, and the sensing surface was composed of multi-walled carbon nanotube (MWCNT) and conducting poly(melamine) (PME). The overoxidation-pretreated MWCNTs affect the surface morphology of the electrodeposited PME and, thus, the interaction with nitrofuran drugs. The characteristics of the nanocomposite-modified electrode surfaces were well characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and surface water contact angle experiments. The nanocomposite-modified electrodes exhibited excellent adsorption and electrochemical reduction of nitrofurans by cyclic voltammetry. The proposed assay exhibited a linear range of sub-micro to micro molar concentrations for the four drugs under the optimized differential pulse voltammetric (DPV) technique. The detection limits were found to be in the nanomolar ranges. The developed assay was applied to detect NFT in two real samples, and the results showed good recoveries that ranged from 99.0 to 104.8% and 98.0 to 103.2% for milk and lake water samples, respectively. Graphical abstract ᅟ.

Poly (glycine) modified carbon paste electrode for simultaneous determination of catechol and hydroquinone: A voltammetric study

The poly (glycine) modified carbon paste electrode (MCPE) was fabricated for the determination of catechol and hydroquinone by cyclic voltammetric and differential pulse voltammetric techniques. The poly (glycine) MCPE exhibits high sensitivity and selectivity in the determination of catechol and hydroquinone in a binary mixture. The effect of scan rate was examined and it was found to be adsorption-controlled. The effect of concentration was studied in the range of 20-180 μM. The limit of detection (3S/M) and limit of quantification (10S/M) for CC were found to be 0.16 μM and 0.55 μM, respectively and for HQ the values were 0.20 μM and 0.66 μM, respectively. In order to show the selectivity of the electrode interference study was performed by varying the concentration of one analyte while keeping another analyte constant. Overall, a simple experimental procedure for fabricating the poly (glycine) MCPE was proposed with the merits of sensitivity, selectivity, reproducibility, and anti-fouling property towards the electroactive species and also in biological matrices.

A state-of-the-art approach for facile and reliable determination of benzocaine in pharmaceuticals and biological samples based on the use of miniaturized boron-doped diamond electrochemical sensor

For the first time, the miniaturized thick-film boron-doped diamond electrode was applied as progressive electrochemical sensor for simple, facile and reliable quantification of local anesthetic agent, benzocaine (BZC). Cyclic voltammetric measurements revealed that the electrode reaction of this analyte was manifested by one irreversible and diffusion-driven oxidation peak at +1.0 V in Britton-Robinson buffer at pH 4.0. Pulse voltammetric techniques with the suitably chosen values of operating parameters were used for the construction of calibration curves for BZC determination with the essential analytical characteristics as follows: the linear concentration range of 0.1–400 μM and 0.4–200 μM, the limit of detection of 80 nM and 100 nM for differential pulse voltammetry (DPV) and square-wave voltammetry (SWV), respectively. The excellent repeatability with the relative standard deviation below 5% was reached for both pulse voltammetric techniques. The developed protocols were applied to analysis of the commercial pharmaceuticals with the recoveries ranging from 97.4 to 104.5% and from 97.0 to 102.7% for DPV and SWV procedures as well as model human urine samples with recoveries from 96.0 to 104.0% and from 98.5 to 100.8%. This platform based on biocompatible, portable and easy-to-operate electrochemical sensor could encourage the viability of the proposed state-of-the-art approach for field applications, such as quality control of pharmaceuticals and monitoring of BZC in biological samples.

Selective electrochemical detection of dopamine based on molecularly imprinted poly(5-amino 8-hydroxy quinoline) immobilized reduced graphene oxide

The dopamine-imprinted conducting polymer film of 5-amino 8-hydroxy quinoline (AHQ) was electrodeposited on reduced graphene oxide (rGO)-modified glassy carbon (GC) electrode and was applied as a molecular recognition element for the selective determination of dopamine. The molecularly imprinted polymer (MIP)-modified electrode showed an excellent affinity towards dopamine due to the presence of imprinted site through hydrogen bonding interaction between dopamine and poly (AHQ) membrane. The molecular recognition ability of MIP-modified electrode was analyzed by cyclic voltammetric and differential pulse voltammetric techniques. The most stable geometry of the template–monomer complex in the pre-polymerization mixture was calculated by computational approaches. The rGO modification augmented both surface area and electron transfer kinetics of the bare electrode. The GC/rGO/MIP electrode possessed 2.83 fold current enhancements when compared to GC/MIP electrode, indicating the improvement in sensitivity due to rGO modification. The limit of detection and sensitivity of GC/rGO/MIP electrode was observed to be 32.7 nM and 13.3 AM−1 cm−2, respectively. The imprinting methodology provided an exceptional selectivity towards the detection of dopamine even in the presence of high concentration of possible physiological interferents. Moreover, the fabricated electrode was successfully employed for the detection of dopamine in human blood plasma samples proving the effectiveness of the sensor for the sensitive detection of dopamine from real samples.

Modification of glassy carbon electrode with poly(hydroxynaphthol blue)/multi-walled carbon nanotubes composite and construction a new voltammetric sensor for the simultaneous determination of hydroquinone, catechol, and resorcinol

A novel voltammetric sensor is developed based on a poly(hydroxynaphthol blue)/multi-walled carbon nanotubes-modified glassy carbon electrode for the simultaneous determination of the dihydroxybenzene isomers hydroquinone (HQ), catechol (CC), and resorcinol (RS). The preparation and basic electrochemical performance of the sensor are investigated in details. The electrochemical behavior of the dihydroxybenzene isomers at the sensor is studied by the cyclic and differential pulse voltammetric techniques. The results obtained show that this new electrochemical sensor exhibits an excellent electro-catalytic activity towards oxidation of the three isomers. The mechanism of this electro-catalytic activity is discussed. Using the optimum parameters, limit of detection obtained 0.24, 0.24, and 0.26 μmol L−1 for HQ, CC, and RS, respectively. The modified electrode is also successfully applied to the simultaneous determination of dihydroxybenzene in water samples.

Interference free detection of dihydroxybenzene isomers at pyrogallol film coated electrode: A voltammetric method

A carbon paste electrode was modified with pyrogallol red film using a cyclic voltammetric method (CV) and the influence of number of sweep segments on the surface area of was examined. The fabricated film coated electrode exhibited excellent electrocatalytic performance for the electro-oxidation of 1, 2- dihydroxybenzene and 1, 4-dihydroxybenzene. To know the kinetics of electrode process, scan rate study was conducted and it confirms the adsorption controlled electrode kinetics. The redox potentials were dependents on pH and witnessed an identical number transfer of protons and electrons. Also a linearity was observed for the peak current and concentration of both HQ and CC by using differential pulse voltammetric technique (DPV) and gave a detection limit of 0.018 and 0.021 μM respectively. Furthermore, successful selective separation of phenolic isomers was achieved in a binary mixture. A good analytical results were observed towards the quantification of CC and HQ in a tap water sample.

Rapid, Sensitive and Simultaneous Determination of Plutonium and Neptunium Using Ruthenium Nanoparticles Decorated Glassy Carbon Electrode

Sensitive determination of actinides is of utmost importance to maintain regular surveillance over the environment in the vicinity of nuclear power plants. The noble metal nanoparticles (NPs) exhibit high electrocatalytic activity, and could be employed for the sensitive and rapid quantifications of plutonium (Pu) and neptunium (Np) ions in the aqueous matrices. Therefore, the Ru NPs decorated glassy carbon electrode (RuNPs/GCE) was examined towards the electrocatalytic redox reaction of Pu and Np respectively. Differential pulse voltammetric (DPV) technique was used for rapid and sensitive quantification of Pu and Np. The RuNPs/GC based DPV technique could be used to determine the concentration of Pu and Np in a few minutes. Both Pu and Np gave sensitive oxidation peaks at 470mV and 840 mV respectively in 1M H2SO4 versus silver/silver chloride electrode. The detection limits were found to be 1.5 μM for Pu and 6.5 μM for Np. The investigated method showed good stability, reproducibility, and repeatability.

Electropolymerized Congo Red Film based Sensor for Dopamine: A Voltammetric Study

The polymerization film of Congo red was prepared on the surface of carbon paste electrode by electropolymerization using cyclic voltammetric method. The higher catalytic activity was obtained for electrocatalytic oxidation of Dopamine, with drastic enhancement of the reversibility and peak current in 0.2 phosphate buffer solution of pH 7.0 at the sweep rate 100 mV/s. The variation of sweep rate and pH were investigated. The limit of detection of Dopamine was found to be 0.06 μM. The effect of interference studies was done by differential pulse voltammetric technique. In the simultaneous look at, Dopamine and Uric acid were well separated by cyclic voltammetric technique. The proposed method showed good sensitivity, selectivity, and reproducibility.

Electrochemical studies of dopamine in presence of uric acid and hydroquinone at TiO2 nanoparticles: a voltammetric study

Commercially available titanium oxide nanoparticles (TiO2NPs) and its stable sensitive voltammetric determination of dopamine in the presence of uric acid and hydroquinone was studied by cyclic voltammetric and differential pulse voltammetric technique. TiO2NPs was characterized by using scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and infrared spectroscopy (IR).The TiO2NPs modified carbon paste electrode (TiO2NPs/MCPE) shows excellent electrochemical enhancement of peak currents for dopamine. The detection limit for dopamine was determined from a differential pulse voltammetric technique was found to be 3.6 × 10−8 M and quantification limit was 12.8 × 10−8 M. The interference studies reveal that the TiO2NPs/MCPE exhibits an excellent selectivity towards dopamine in the presence of large excess of uric acid and hydroquinone. From the concentration study, the oxidation of dopamine was found to be adsorption controlled. The use of TiO2NPs/MCPE is demonstrated for the detection of dopamine in blood serum and injection samples.

Development of an Electrochemical Sensor Based on Covalent Molecular Imprinting for Selective Determination of Bisphenol‐A

AbstractIn this study, an electrochemical sensor was developed and used for selective determination of bisfenol‐A (BPA) by integrating sol‐gel technique and multi‐walled carbon nanotubes (MWCNTs) modified paste electrode. BPA bounded by covalently to isocyanatopropyl‐triethoxy silane (ICPTS) was synthesized as a new precursor (BPA‐ICPTS) and then BPA‐imprinted polymer (BPA‐IP) sol‐gel was prepared by using tetramethoxysilane (TMOS) and BPA‐ICPTS. Non‐imprinted polymer (NIP) sol‐gel was obtained by using TMOS and (3‐Aminopropyl) triethoxysilane. Both BPA‐IP and NIP sol‐gels were characterized by nitrogen adsorption‐desorption analysis, FTIR, SEM, particle size analyzer and optical microscope. Carbon paste sensor electrode was fabricated by mixing the newly synthesized BPA‐IP with MWCNTs, graphite powder and paraffin oil. The electrochemical characterization of the sensor electrode was achieved with cyclic and differential pulse voltammetric techniques. The response of the developed sensor under the most proper conditions was linear in BPA concentration range from 4.0×10−9 to 1.0×10−7 mol L−1 and 5.0×10−7 to 5.0×10−5 mol L−1 and the detection limit was 4.4×10−9 mol L−1. The results unclosed that the proposed sensor displayed high sensitivity and selectivity, superior electrochemical performance and rapid response to BPA.