Differential Pulse Voltammetry Modes Research Articles

Gold nanoparticles decorated kaolinite mineral modified screen-printed electrode: Use for simple, sensitive determination of gallic acid in food samples

The current study offers the nanomolar quantification of gallic acid (GAL) based on gold nanoparticles (AuNps) and kaolinite minerals (KNT) modified on a screen-printed electrode (SPE). The electrochemical behavior of GAL was performed using differential pulse voltammetry (DPV) in Britton Robinson (BR) buffer solution at pH as a supporting electrolyte. Under the optimized DPV mode parameters, the oxidation peak current of GAL (at 0.72 V vs Ag/AgCl) increased linearly in the range between 0.002 μmolL−1 and 40.0 μmolL−1 with a detection limit of 0.50 nmolL−1. The effect of common interfering agents was also investigated. Finally, the applicability of the proposed method was verified by quantification analysis of GAL in black tea and pomegranate juice samples.

"Two-in-One" PtPdCu Trimetallic Multifunctional Nanoparticles-Mediated Dual-Signal-Integrated Aptasensor for Ultradetection of Enrofloxacin.

Balancing the accuracy and simplicity of aptasensors is a challenge in their construction. This study addresses this issue by leveraging the remarkable loading capacity and peroxidase-like catalytic activity of PtPdCu trimetallic nanoparticles, which reduces the reliance on precious metals. A dual-signal readout aptasensor for enrofloxacin (ENR) detection is designed, incorporating DNA dynamic network cascade reactions to further amplify the output signal. Exploiting the strong loading capacity of PtPdCu nanoparticles, they are self-assembled with thionine (Thi) to form a signal label capable of generating signals in two independent modes. The label exhibits excellent enzyme-like catalytic activity and enhances electron transfer capabilities. Differential pulse voltammetry (DPV) and square-wave voltammetry (SWV) are employed to independently read signals from the oxidation-reduction reaction of Thi and the catalytic oxidation of hydroquinone (HQ) to benzoquinone (BQ) by H2O2. The introduced DNA dynamic network cascade reaction modularizes sample processing and electrode surface signal generation, avoiding electrode contamination and efficiently increasing the output of the catalyzed hairpin assembly (CHA) cycle. Under optimized conditions, the developed aptasensor demonstrates detection limits of 0.112 (DPV mode) and 0.0203 pg/mL (SWV mode). Additionally, the sensor successfully detected enrofloxacin in real samples, expanding avenues for designing dual-mode signal amplification strategies.

Electrochemical detection of paracetamol using zeolitic imidazolate framework and graphene oxide derived zinc/nitrogen-doped carbon

A composite of zeolitic imidazolate frameworks and graphene oxide (ZIF-GO) derived 3D–2D Zn/N-doped carbon (ZnNC-rGO) was developed for the electrochemical detection of the analgesic paracetamol (PCT). The pyrolysis of ZIF-GO led to the formation of a nanoscale structure featuring ZnNC cubes embedded in rGO sheets. The Zn0-to-ZnO phase transition was found to mediate electrons during the reversible paracetamol redox reactions, which contributed to the sensing current response. Upon 800 °C heating under a N2 atmosphere, the mesoporosity of ZnNC-rGO(800) was significantly enhanced, thereby increasing the electrochemical surface area and charge transfer efficiency. The electrode sensitivity was optimized at a calibration linearity of 0.526 μA μM−1) with detection limit (0.077 μM) in the range of 0.5 – 70 μM using differential pulse voltammetry mode (DPV). The precision of analytical recovery for trace paracetamol concentrations was maintained based on the excellent reproducibility and selectivity trials in the presence of interference chemicals and in real water samples.

Electrochemical assay of acetamiprid in vegetables based on nitrogen-doped graphene/polypyrrole nanocomposites.

Dual-mode electrochemical aptasensor based on nitrogen-doped graphene (NG) doped with the conducting polymer polypyrrole (PPy) nanocomposite is proposed for the determination of acetamiprid. NG/PPy was electrodeposited onto the glassy carbon electrode (GCE) using cyclic voltammetry technique. NG/PPy/GCE showed outstanding electrocatalytic activity for the oxidation of nitrite due to "active region" induced by the charge redistribution of carbon atoms. The ultrasensitive dual-mode biosensor for acetamiprid could be easily developed by coupling acetamiprid aptamers with the NG/PPy hybrid. The specific binding between acetamiprid and the aptamers resulted in the increase of differential pulse voltammetry (DPV) signal change and the decrease of chronoamperometry (CA) signal, and the concentration of acetamiprid could be measured. The working potentials of DPV and CA were - 0.2 ~ 0.4V and - 0.4 ~ 0.4V (vs. SCE), respectively. The dual-mode acetamiprid biosensor showed a wide linear range from 10-12 to 10-7gmL-1, with low detection limits of 1.15 × 10-13gmL-1 and 7.32 × 10-13gmL-1 through DPV and CA modes, respectively. Moreover, owing to high active area and superior conductivity, as well as good electrocatalytic ability, the dual-sensing platform based on NG/PPy nanocomposite supported the quantification of acetamiprid in complex samples. A dual-mode electrochemical aptasensor based on NG/PPy nanocomposite for acetamiprid detection was proposed through both the increase of differential pulse voltammetry (DPV) signal change and the decrease of chronoamperometry (CA) signal of the nitrite oxidation electrocatalyzed by NG/PPyn in sensors and biosensors.

Electrochemical behavior of chloramphenicol on carbon electrodes in a microelectrochemical cell

Express determination of antibiotics is an extremely important task today. Portable electrochemical microdevices are a viable alternative to traditional methods of analysis. The development of such devices requires the study of redox processes in detail. This article is devoted to the comparative study of the electrochemical behavior of chloramphenicol in water solvents in standard laboratory and portable microelectrochemical cells. It was found that the electrochemical reduction of chloramphenicol proceeds via a 3-electron mechanism to the formation of a dimer. In the transition from the macrocell to the microcell, a decrease in the electrochemical reduction current and a shift of the peak potential to the cathode region are observed, which is apparently associated mainly with the type of the electrode material. The best characteristics of the direct electrochemical response were obtained in the differential pulse voltammetry mode. Under the selected operating parameters, the peak current of the electrochemical reduction of chloramphenicol is linearly dependent on the concentration of the antibiotic in the range of 2∙10–3–1∙10–5 M with a detection limit of 3∙10–5 M. Obtained characteristics are sufficient for the quality control of pharmaceuticals and can be improved through the use of organic and hybrid modifiers of the working electrode surface.

Dual mode competitive electrochemical immunoassay for dibutyl phthalate detection based on PEI functionalized nitrogen doped graphene-CoSe2/gold nanowires and thionine-Au@Pt core-shell

In this work, a sensitive dual mode competitive electrochemical immunosensor based on differential pulse voltammetry (DPV) and square wave voltammetry (SWV) response modes for quantitative determination of dibutyl phthalate (DBP) was successfully established. According to diethylenetriamine (DETA) assisted hydrothermal strategy, a novel N-doped graphene/CoSe2 nanobelt composite was prepared. Afterwards, PEI functionalized NG-CoSe2 and gold nanowires (AuNWs) were further compounded as a preliminary signal amplification platform for immunosensor. Thionine (Thi)-loaded [email protected] and secondary antibody (Ab2) connected as a signal label. The immobilized coating antigen DBP-BSA and the DBP compete for limited antibody binding sites. The concentration of DBP can be determined by DPV detect the Thi signal loaded on the [email protected]2 label. It can also be determined by SWV mode to detect the current generated by the reaction system of H2O2 and o-phenylenediamine (o-PD) catalyzed by [email protected] with peroxidase like properties. Under optimum conditions, the linear ranges of the DPV and SWV modes were 1 pg mL−1∼1 μg mL−1. And LOD were 0.486 pg mL-1 (DPV) and 0.711 pg mL-1 (SWV), respectively. Besides, it exhibited outstanding selectivity, reproducibility, stability and can be used for sensitive detection of DBP in real samples.

Chiral single-walled carbon nanotubes as chiral selectors in multimode enantioselective sensors.

Single-walled carbon nanotube-(7,6) chirality was used for the design of multimode enantioselective sensors using different carbon matrices such as graphene paste, graphite paste, and carbon nanopowder-based paste. l- and d-malic acids were used as model analytes. The responses of the multimode sensors were evaluated for potentiometric and differential pulse voltammetry (DPV) modes. When carbon nanopowder was used as matrix, the multimode sensor was enantioselective for d-malic acid in the concentration range 10-3 to 10-15 mol/L for the potentiometric mode and 10-5 to 10-8 mol/L for the DPV mode. The graphite paste-based sensor was enantioselective for l-malic acid in the ranges: 10-10 to 10-13 for the potentiometric mode and 10-4 to 10-7 mol/L for the DPV mode. The sensors based on graphene and chiral single-walled carbon nanotubes were enantioselective for d-malic acid, and a response was obtained only in the DPV mode. Accordingly, the matrix influenced both the enantioselectivity and the sensitivity of the measurements. The application of the sensors was for the enantioanalysis of malic acid in wines and apple juice samples. The proposed method is fast and reliable and allows the quantification of l- and d-malic acids using electrochemical methods based on different principles, from the real samples after a buffering of the samples. The enantioanalysis of malic acid in wine and juice samples was performed with high recoveries (higher than 90.00%) and low relative standard deviation (RSD) (%) values (lower than 1.00%).

Study of electrochemical behavior of escitalopram oxalate using hanging mercury drop electrode and its determination in human urine and pharmaceuticals

Escitalopram oxalate (ESC-OX) is among the most currently used antidepressant drugs. This study aimed to determine ESC-OX in human urine and different pharmaceutical dosage forms via the electrochemical method. The electrochemical behavior of ESC-OX was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques at hanging mercury dropping electrode (HMDE). The maximum reduction potential was determined to be − 0.55 and − 0.57 V at pH 6.5 in a cell containing 5% (v/v) methanol and 0.3 M KCl. Under the optimized conditions, the calibration curve of the cathodic peak current versus the concentration was linear in the range of 4.143–29.0 µg mL−1. The LOD and LOQ were found to be 1.15 µg mL−1 and 1.31 µg mL−1, 3.490 µg mL−1 and 3.97 µg mL−1 for pharmaceutical and urine samples, respectively. The investigation of electrochemical reduction of ESC-OX on the HDME by using CV resulted in a quasi-reversibility, mainly diffusion-controlled reaction that involves a four-electron reduction of the nitrile group. For analytical purposes, a stable and well-defined peak was obtained in DPV mode. The average accuracy was found to be 101.60% ± 0.48 and 99.72% ± 5.64 for pharmaceutical and urine samples, respectively. Moreover, the developed method was precise with RSD % below 2% for both samples. The validation of the developed method was carried out as stated in the ICH Q2(R) 1 guideline. The proposed technique was effectively utilized for the determination of ESC-OX in different pharmaceutical formulations and urine samples. Neither excipients nor endogenous substances have electroactive interferences.

Nano Structured and Pyrolytic Deposited Carbon Electrodes for Detection of Nitroaromates – a Comparison

IntroductionNitroaromatics like 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT) are long-lasting organic pollutants in natural water and soil caused mainly by the military usage. Nano structured electrodes are established in detection of such compounds in water by linear sweep voltammetry (DP) [1]. On the other hand, it could be shown that screen printed carbon electrodes [2] and such made of pyrolytic deposited carbon are also suited for that purpose [3]. Both kind of electrodes were investigated regarding the determination of nitroaromatic compounds in aqueous solution. The aim of this paper is to compare the performance of both electrodes in comparison to commercial electrodes respecting sensitivity, selectivity and long-term stability.ExperimentalElectrodes using carbon nano-tubes and gold nano-particles on printed carbon are commercially available (DropSens, Spain DRP-110CNT-GNP). Screen printed electrodes (SPCE) of 3mm in diameter were industrially like produced on an alumina substrate with a commercial carbon ink (DuPont) carbon paste. Pyrolytic graphite layer were deposited by high temperature decomposition (1050 °C) of aromatic vapor for 15 min with high reproducibility (PyGE). Solid state analyses as XRD and SEM analysis show crystalline carbon with a sp2 hybridization (Fig. 1). The setup of the electrodes is seen in Fig. 2. All experiments were performed in a three electrode arrangement using platinum counter electrode and Ag/AgCl,Cl--reference electrode in a buffer solution. Voltammetric experiments were performed by a PalmSens potentiostate (Palm Instruments, NL). DRP-110CNT-GNP were investigated by linear sweep voltammetrie. SPCE and PyGE were measured in differential pulse voltammetry mode (DPV). The parameter for the DPV were selected as follows: scan rates of 15 mV∙s-1 to 20 mV∙s-1, amplitude of 50 mV and step height of 5 mVResults and discussionThe potentials of the single reduction peak of nitro-aromates can be clearly separated (Fig. 3) for both kind of electrodes, SPCE and PyGE. The nitroaromates trinitrotoluene (TNT) and dinitrotoluene (DNT) are reduced and dopamine is oxidized in DPV mode (Fig.4). The peak currents are proportional to the TNT concentrations with a sensitivity of 2.7 nA/ppb for SPCE (Fig.5) and 0.78 for PyGE (Fig. 6) at the characteristic peak potential of -0.59 V (R²=0.99). Commercial electrodes DRP-110CNT-GNP made of carbon with gold nano particles require a special treatment in cyclo-voltammertic mode up to stable measuring conditions. The sensitivity of 2.8 nA/ppb is high compared to PyGEs. The relative errors in measuring cycles (35 %) are very much higher than those for PyGEs (5 %). PyGE do not need a special pretreatment before use.Screen printed and pyrolytic deposited carbon electrodes can be applied in air saturated aqueous solutions like in field application. For both electrodes, SCPE and PyGE, the oxygen reduction peak do not interfere with the reduction of the nitro groups. The manufacturing tolerances become smaller in the row DRP-110CNT-GNP, SPCE, PyGE. PyGEs can be produced in few steps with very small deviations. They can stored in air or in water over years without a loss of performance. Commercial electrodes are very complex in setup and obviously not so easy to produce in proper quality. Furthermore, their signals are remarkably influenced by oxygen so that measurements in air are not possible.

Dual-Mode Electrochemical Assay of Prostate-Specific Antigen Based on Antifouling Peptides Functionalized with Electrochemical Probes and Internal References.

Sensitive and selective detection of target analytes in complex biological samples is currently a major challenge. Herein we constructed a dual-mode antifouling electrochemical sensing platform for the detection of prostate-specific antigen (PSA) based on two kinds of antifouling peptides functionalized with a graphene oxide-Fe3O4-thionine (GO-Fe3O4-Thi) probe and internal reference ferrocene (Fc), respectively. The longer peptide (Pep1) modified with the GO-Fe3O4-Thi probe was designed to contain a peptide sequence (HSSKLQK) capable of being recognized and cut by PSA. The GO-Fe3O4-Thi probe functions not only as a peroxidase mimick (GO-Fe3O4) but also works as an electrochemical probe due to the presence of thionine (Thi). The concentration of PSA can be measured through both the increase of differential pulse voltammetry (DPV) signal change of Thi and the decrease of chronoamperometry (CA) signal of the reduction of H2O2 electrocatalyzed by GO-Fe3O4. The shorter peptide (Pep2) was tagged with Fc, whose DPV signal remained constant and was independent of the presence of PSA, and it was used as an internal reference to ensure the reliability and accuracy of the measurement. The dual-mode PSA sensor exhibits a wide linear range from 5 pg/mL to 10 ng/mL, with low detection limits of 0.76 and 0.42 pg/mL through DPV and CA modes, respectively. More importantly, owing to the antifouling capability of the designed peptides, the biosensor performances remained operable even in human serum, indicating feasibility of the electrochemical biosensor for practical PSA quantification in complex samples.

Iron oxide (Fe2O3) nanoparticles modified carbon paste electrode as an advanced material for electrochemical investigation of paracetamol and dopamine

Abstract The electrochemical behavior of paracetamol (PA) and dopamine (DA) has been investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV) using a selective and sensitive iron oxide (Fe2O3) nanoparticle modified carbon paste electrode (IOCPE). The PA and DA showed an anodic peak potential at 0.458 V and 0.247 V and a cathodic peak potential at 0.088 V and 0.11 V (vs Ag/AgCl), respectively. In the DPV mode, PA and DA gave linear responses over the concentration range of 2–150 μM (R2 = 0.998) and 2–170 μM (R2 = 0.989), respectively. The limit of detection (LOD = 3 s/m) for PA and DA were found to be 1.16 and 0.79 μM, respectively. IOCPE possesses an excellent electrocatalytic activity towards the determination of PA and DA. The proposed method could be successfully validated for the simultaneous and individual determination of PA and DA present in pharmaceutical and real samples.

OH functionalized Multi-Walled Carbon Nanotube modified electrode as electrochemical sensor for the detection of Aceclofenac

ABSTRACTThe rapid electrochemical determination of Aceclofenac (ACF) has been employed by cyclic voltammetry (CV), differential pulse voltammetry (DPV) using developed OH-functionalised multiwalled carbon nanotube carbon paste electrode (OH-MWCNT/CPE). Modified electrode was characterised by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), X-ray diffraction spectroscopy (XRD), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The ACF exhibits two oxidation peaks at +0.4 V, +0.66 V and one reduction peak at +0.3 V. The active surface area of the bare carbon paste electrode (BCPE) and modified electrode have been characterised by using K3[Fe(CN)6] solution containing 0.1 M KCl. In DPV mode, variation of ACF gave the limit of detection (LOD = 3s/m) 0.246 μM over the concentration range 1.0 to 190.0 μM (R2 = 0.9994). The developed electrode has good stability, reproducibility and could be successfully validated for the detection of ACF in pharmaceutical samples and biological fluids.

Dual-Mode Electrochemical Immunoassay for Insulin Based on Cu7S4-Au as a Double Signal Indicator.

The detection of insulin by electrochemical (EC) immunoassay is desirable but highly challenged due to the obstacle of improving its accuracy, especially in a single-response system. In this work, based on Cu7S4-Au as a dual signal indicator, we fabricated a dual-mode electrochemical immunoassay for insulin. Especially, Cu7S4 presents a strong differential pulse voltammetry (DPV) signal for the electron transfer between Cu2+ and Cu+, without the addition of K3[Fe(CN)6] or other electron transfer mediators. Furthermore, Cu7S4 displays high sensitivity and high electrocatalytic activity toward the reduction of H2O2 through chronoamperometry (CA). The introduction of Au nanoparticles can not only link on the surface of Cu7S4 by the chemical bond of Au-SH, but also connect the second antibody (Ab2) by the chemical bond of Au-N. Due to the superior electroconductivity of Au nanoparticles and the synergistic effect between the Au nanoparticles and Cu7S4, a high sensitivity is achieved by means of DPV and CA. To improve the loading capacity of antibodies, nanofiber polyaniline covalently grafted graphene (GS-PANI) linked with Au nanoparticles (GS-PANI-Au) as the matrix material was prepared. Based on Cu7S4-Au as a double signal indicator, the developed EC immunoassay for insulin exhibits a wide linear response for insulin detection in the range from 0.1 pg/mL to 50 ng/mL, with a low detection limit of 35.8 and 12.4 fg/mL through DPV and CA modes, respectively. Furthermore, the immunosensor displays an excellent analytical capability for insulin and promises application in quantitative detection of other disease markers in clinical diagnosis.

Multimode sensors as new tools for molecular recognition of testosterone, dihydrotestosterone and estradiol in children's saliva.

Increased levels of testosterone (T2 ), dihydrotestosterone (DHT) and estradiol (E2 ) in children may be responsible for their early/delayed puberty and obesity conditions. Therefore, multimode sensors based on carbon matrices, such as graphite, graphene, fullerene C60 and multiwall carbon nanotubes modified with maltodextrin, were designed to assess reliably T2 , DHT and E2 in children saliva. The modes used for the assay of hormones were stochastic mode (for qualitative and quantitative determination of hormones) and differential pulse voltammetry mode (for quantitative determination of hormones). The advantage of this type of sensors, for hormone analysis, is their possibility to reach low concentration levels- are placed for children saliva under the detection limit of standard methods (e.g. ELISA used for the determination of these hormones in saliva). This made the multimode sensors an excellent tool for clinical analysis and especially for determination of substances of clinical importance in saliva samples. The proposed method is fast and simple, and no sampling of saliva is required.

Multimode Microsensors Based on Carbon Matrices Used for the Assay of IL-6 in Whole Blood Samples

High levels of interleukin-6 (IL-6) are associated with different diseases like prostate cancer, breast cancer, stress, cardiovascular diseases and obesity. Therefore, a fast and simple method of screening of IL-6 is needed to early diagnose these diseases and reduce mortality rate. Multimode microsensors (microsensors that can operate in both stochastic and differential pulse voltammetry modes) based on carbon matrices, such as graphite, graphene, fullerene (C60) and multiwall carbon nanotubes modified with maltodextrin were designed for the assay of IL-6 in whole blood samples. Multimode sensing is a good alternative for classic methods because it provides quantitative (response obtained in both stochastic and DPV mode) and qualitative analysis (response obtained in stochastic mode) in short time (6 min), with no sampling pretreatment. The lowest limit of determination (10 fg/mL) was recorded using the multimode microsensor based on MD and fullerene (C60) in stochastic mode.

Molecular recognition of HER-1 in whole-blood samples.

Multimode sensing was proposed for molecular screening and recognition of HER-1 in whole blood. The tools used for molecular recognition were platforms based on nanostructured materials such as the complex of Mn(III) with meso-tetra (4-carboxyphenyl) porphyrin, and maltodextrin (dextrose equivalence between 4 and 7), immobilized in diamond paste, graphite paste or C60 fullerene paste. The identification of HER-1 in whole-blood samples, at molecular level, is performed using stochastic mode and is followed by the quantification of it using stochastic and differential pulse voltammetry modes. HER-1 can be identified in the concentration range between 280 fg/ml and 4.86 ng/ml using stochastic mode, this making possible the early detection of cancers such as gastrointestinal, pancreatic and lung cancers. The recovery tests performed using whole-blood samples proved that the platforms can be used for identification and quantification of HER-1 with high sensitivity and reliability in such samples, these making them good molecular screening tools.

Electroactive behavior assessment of poly(acrylic acid)‐graphene oxide composite hydrogel in the detection of cadmium

ABSTRACTSuper absorbent polymers of acrylic acid‐graphene oxide (PAA‐GO) were synthesized with different percentage of chemical neutralization (0, 10, and 20%) of the acrylic acid monomer before its polymerization. The influence of their swelling and adsorption/desorption capacity of cadmium ions in aqueous solutions were studied and revealed that the GO enables greater mechanical stability in the materials. The PAA hydrogels, with the same degrees of neutralization, were also prepared without GO to compare with the composites. Additionally, carbon paste electrodes (CPE) modified with the composites PAA‐GO were used to asses and compare their adsorption properties with cadmium(II). The anodic stripping voltammetry (ASV) peak, in the differential pulse voltammetry mode, for cadmium oxidation was found to be influenced by the presence of GO into the polymer, and also by their percentage of neutralization. The accumulation of cadmium(II) on the surface of the modified CPEs was performed under open‐circuit conditions taking an account the preconcentration time of the metal cation. The presence of GO enhances the electrical signal of the electrodes in short times of immersion in cadmium(II) solutions. This property contributed to get linear responses of the CPEs modified with the composites, which were influenced by their degrees of neutralization. The PAA‐GO 10N electrode with 10% of neutralization combined the influence of GO and the degree of neutralization in the same matrix, and also showed good performance in terms of its mechanical stability, it was chosen for preliminary studies on the selectivity of the electrode toward Zn(II) and Cu(II). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40846.

Conducting polyaniline-graphene oxide fibrous nanocomposites: preparation, characterization and simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid

Polyaniline/graphene oxide (PANI-GO) fibrous nanocomposites have been prepared and the electrochemical catalytic activity towards the electro-oxidation of ascorbic acid (AA), Dopamine (DA) and Uric acid (UA) has been investigated. The nanocomposites were synthesized via an in situ chemical polymerization method. The morphology, composition, thermal and electrochemical properties of the resulting nanocomposites were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, FT-IR spectroscopy, thermo gravimetric analysis and cyclic voltammetry. The catalytic behavior of PANI-GO nanocomposite modified glassy carbon electrode (GCE) towards AA, DA and UA has been investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV). The PANI-GO/GCE showed excellent catalytic activity towards electrochemical oxidation of AA, DA and UA compared to the bare GCE. The electrochemical oxidation signal of AA, DA and UA are well separated into three distinct peaks with peak potential separation of 343 mV, 145 mV and 488 mV between AA-DA, DA-UA and AA-UA respectively in CV studies and the corresponding peak potential separation in DPV mode are 320 mV, 230 mV and 550 mV. Under the optimized DPV experimental conditions, the peak current of AA, DA and UA give linear response over the range of 25–200 μM (R2 = 0.9955), 2–18 μM (R2 = 0.9932) and 2–18 μM (R2 = 0.9902) with detection limit of 20 μM, 0.5 μM and 0.2 μM at S/N = 3, respectively. The attractive features of PANI-GO provide potential applications in the simultaneous detection of AA, DA and UA. The excellent electrocatalytic behavior of PANI-GO may lead to new applications in electrochemical analysis.

Functionalized-graphene modified graphite electrode for the selective determination of dopamine in presence of uric acid and ascorbic acid

Graphene is chemically synthesized by solvothermal reduction of colloidal dispersions of graphite oxide. Graphite electrode is modified with functionalized-graphene for electrochemical applications. Electrochemical characterization of functionalized-graphene modified graphite electrode (FGGE) is carried out by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The behavior of FGGE towards ascorbic acid (AA), dopamine (DA) and uric acid (UA) has been investigated by CV, differential pulse voltammetry (DPV) and chronoamperommetry (CA). The FGGE showed excellent catalytic activity towards electrochemical oxidation of AA, DA and UA compared to that of the bare graphite electrode. The electrochemical oxidation signals of AA, DA and UA are well separated into three distinct peaks with peak potential separation of 193mv, 172mv and 264 mV between AA–DA, DA–UA and AA–UA respectively in CV studies and the corresponding peak potential separations in DPV mode are 204mv, 141mv and 345mv. The FGGE is successfully used for the simultaneous detection of AA, DA and UA in their ternary mixture and DA in serum and pharmaceutical samples. The excellent electrocatalytic behavior of FGGE may lead to new applications in electrochemical analysis.

Electrochemical oxidation behavior of nitrite on a chitosan-carboxylated multiwall carbon nanotube modified electrode

A novel chitosan-carboxylated multiwall carbon nanotube modified glassy carbon electrode (MC/GCE) was developed to investigate the oxidation behavior of nitrite using cyclic voltammetry and differential pulse voltammetry modes. The electrochemical mechanism of the MC/GCE towards nitrite was discussed. The MC/GCE exhibited fast response towards nitrite with a detection limit of 1 × 10 −7 mol l −1 and a linear range of 5 × 10 −7–1 × 10 −4 mol l −1. The possible interference from several common ions was tested. The proposed method was successfully applied in the detection of nitrite in real samples.