Differential Pulse Anodic Voltammetry Research Articles

Selective Voltammetric Sensor for the Simultaneous Quantification of Tartrazine and Brilliant Blue FCF.

Tartrazine and brilliant blue FCF are synthetic dyes used in the food, cosmetic and pharmaceutical industries. The individual and/or simultaneous control of their concentrations is required due to dose-dependent negative health effects. Therefore, the paper presents experimental results related to the development of a sensing platform for the electrochemical detection of tartrazine and brilliant blue FCF based on a glassy carbon electrode (GCE) modified with MnO2 nanorods, using anodic differential pulse voltammetry. Homogeneous and stable suspensions of MnO2 nanorods have been obtained involving cetylpyridinium bromide solution as a cationic surfactant. The MnO2 nanorods-modified electrode showed a 7.9-fold increase in the electroactive surface area and a 72-fold decrease in the electron transfer resistance. The developed sensor allowed the simultaneous quantification of dyes for two linear domains: in the ranges of 0.10-2.5 and 2.5-15 μM for tartrazine and 0.25-2.5 and 2.5-15 μM for brilliant blue FCF with detection limits of 43 and 41 nM, respectively. High selectivity of the sensor response in the presence of typical interference agents (inorganic ions, saccharides, ascorbic and sorbic acids), other food dyes (riboflavin, indigo carmine, and sunset yellow), and vanillin has been achieved. The sensor has been tested by analyzing soft and isotonic sports drinks and the determined concentrations were close to those obtained involving the chromatography technique.

Bioremoval of Different Heavy Metals in Industrial Effluent by the Resistant Fungal Strain Aspergillus niger

Developing countries are increasingly concerned with pollution due to toxic heavy metals in the environment. Unlike most organic pollutants which can be destroyed, toxic metal ions released into the environment often persist indefinitely circulating and eventually accumulating throughout the food chain thus posing a serious threat to mankind. The use of biological materials for heavy metal removal or recovery has gained importance in recent years due to their good performance and low cost. Among the various sources, both live and inactivated biomass of organisms exhibits interesting metal binding capacities. Their complex cell walls contain high content of functional groups like amino, amide, hydroxyl, carboxyl, and phosphate which have been implicated in metals binding. In the present study, Aspergillus niger was used to analyze the metal uptake from an aqueous solution. The determination of Cu+2, Pb+2, Cd+2, Zn+2, Co-2 and Ni+2 in samples was carried out by differential Pulse Anodic Voltammetry (DPASV) and the Voltammograms. Production of oxalic acid was carried out by submerged fermentation. The organism used in the present study has the ideal properties to sequester toxic metals and grow faster.

Electrochemical N-Acetyl-β-D-glucosaminidase Urinalysis: Toward Sensor Chip-Based Diagnostics of Kidney Malfunction.

N-Acetyl-β-D-glucosaminidase (GlcNAcase) is a valuable biomarker for kidney health, as an increased urinary level of the enzyme indicates cell damage within the renal tubular filtration system from acute or chronic organ injury or exposure to nephrotoxic compounds. Effective renal function is vital for physiological homeostasis, and early detection of acute or chronic renal malfunction is critically important for timely treatment decisions. Here, we introduce a novel option for electrochemical urinalysis of GlcNAcase, based on anodic differential pulse voltammetry at boron-doped diamond disk sensors of the oxidizable product 4-nitrophenol (4NP), which is released by the action of GlcNAcase on the synthetic substrate 4NP-N-acetyl-β-D-glucosaminide (GlcNAc-4NP), added to the test solution as a reporter molecule. The proposed voltammetric enzyme activity screen accurately distinguishes urine samples of normal, slightly elevated and critically high urinary GlcNAcase content without interference from other urinary constituents. Moreover, this practice has the potential to be adapted for use in a hand-held device for application in clinical laboratories by physicians or in personal home health care. Evidence is also presented for the effective management of the procedure with mass-producible screen-printed sensor chip platforms.

Voltammetric Determination of Hesperidin on the Electrode Modified with SnO2 Nanoparticles and Surfactants

AbstractHighly sensitive voltammetric method for hesperidin determination is developed using glassy carbon electrode modified with SnO2 nanoparticles (SnO2 NPs) and surfactants. The highest oxidation currents of hesperidin are observed in the case of cationic 0.50 mM cetylpyridinium bromide (CPB). Parameters of hesperidin electrooxidation have been calculated. Adsorptive anodic differential pulse voltammetry (AdADPV) in phosphate buffer pH 7.0 after 120 s accumulation provides linear dynamic ranges of 0.10–10 and 10–75 μM with the detection limit of 0.077 μM. The selectivity of hesperidin response is proved in the presence of inorganic ions, saccharides, ascorbic acid and other natural phenolics.

Development of a fast and sensitive method for the determination of As(III) at trace levels in urine by differential pulse anodic voltammetry using a simple graphene screen–printed electrode

A simple and fast anodic voltammetric method was employed to determine traces of As(III) in urine samples using commercial screen–printed graphene electrodes without subsequent modification. To obtain a sensitive and selective method for As(III) determination, the effects of various parameters such as pH, supporting electrolyte concentration, accumulation potential (Eacc), accumulation time (tacc), and potential scan conditions were studied. The optimum experimental conditions were chosen to be as follows: pH of 2.8 (0.01 mol L−1 phosphate buffer), scan increment of 4 mV, pulse width of 80 ms, pulse period of 0.5 s, and pulse amplitude of 200 mV. Differential pulse voltammograms were obtained by scanning from −0.80 V to 0.80 V without applying an accumulation step. Under these conditions, one peak was observed at 0.27 V due to As0 oxidation. After optimizing the experimental conditions, the anodic peak current for As was found to be linearly related to its concentration up to ca. 5.0 μg L−1, with detection and quantitation limits (DLs, QLs) of 0.28 µg L−1 and 0.92 µg L−1, respectively. The developed method was validated by the determination of As(III) in spiked tap water from our laboratory, which showed an As(III) concentration of 50.64 ± 0.10 μg L−1 (spiked with 50.0 μg L−1); two urine samples (where As was not detected) spiked with As(III) 0.73 μg L−1 and 0.91 μg L−1 (in the cell) showed an As(III) concentration of 0.70 μg L−1 and 0.91 μg L−1, respectively. The method was successfully applied to the determination of Astotal in 16 urine samples obtained from workers occupationally exposed to inorganic arsenic compounds without previous treatment. The results obtained for Astotal were compared with measurements made by an external analytical laboratory, which used HG–AAS. To determine Astotal, As(V) was reduced in the presence of thiosulfate in an acid medium. The electrode showed good stability and repeatability.

L-ARGININE DETERMINATION IN BIOLOGICALLY ACTIVE ADDITIVE BY VOLTAMMETRY

This article reports about the electrochemical determination of L-arginine on a glassy carbon electrode in a dietary supplement using anodic differential pulse voltammetry. The exponential depense of the peak current on the square root of the scan rate (I/v1/2), the shifts of the potential to the negative area and linear correlation between peak potential and logarithm of the scan rate (lg(v)) confirms that electrooxidation of L-arginine is an irreversible process. Moreover, the criteria of Semerano equals 0.4 may indicate the process of electrooxidation without adsorption. The effect of pH, accumulation potential, accumulation time and scan rate was tested on electrochemical behavior of L-arginine. Working conditions for L-arginine determination in model media are following: pH 13; Eacc 0.3 V, tacc 30 s; v = 60 mV s-1. A linear dependence of L-arginine electrooxidation current on its concentration was observed at the 0.9 V in the range between 1.0∙10-4 and 10∙10-4 mol l-1. The detection limit was 1.34∙10-6 mol l-1. A comparative determination of L-arginine in dietary supplement was carried out by the voltammetric method and capillary electrophoresis. Thus, the determination of L-arginine in a dietary supplement on a glassy carbon electrode in NaOH solution (pH 13) was successfully carried out using anodic differential pulse voltammetry. The proposed method does not require sample preparation and allows to quickly determine L-arginine in dietary supplement.

Voltammetric Detection of Catechol and Dopamine Based on a Supramolecular Composite Prepared from Multifarene[3,3] and Reduced Graphene Oxide

AbstractA selective and sensitive modified‐electrode for catechol and dopamine was presented with supramolecular recognition accomplished by making use of the macrocyclic host multifarene[3,3] that was used as a composite with reduced graphene oxide. The morphologies and electrochemical nature of the composite were characterized by atomic force microscopy, transmission electron microscopy, cyclic voltammetry and differential pulse anodic voltammetry. The modified electrode, best operated at a potential around 0.16 V vs. Ag/AgCl, displayed a differential pulse voltammetric response in the linear concentration range of 10–100 nM within a detection limit of 0.51 nM (at S/N=3). It was further applied to detect dopamine (at a working potential of 0.18 V vs. Ag/AgCl) in the linear concentration range of 10–100 nM with a detection limit of 0.62 nM. The modified electrode also exhibited satisfactory results to the determination of dopamine injections. The constructed modified electrode for dopamine detection was investigated in the presence of the interfering substances including glucose, urea and ascorbic acid, indicating a good selectivity.

An enzyme-free sensing platform based on molecularly imprinted polymer/MWCNT composite for sub-micromolar-level determination of pyruvic acid as a cancer biomarker.

Pyruvic acid (PA) has been demonstrated to be an important cancer biomarker. Herein, carbon/carbon nanotube paste electrode was modified with the newly synthesized PA-imprinted polymer (MIP) and used as an enzyme-free sensor for PA assay. Methacrylic acid and ethylene glycol dimethacrylate were copolymerized in the presence of PA to prepare PA-IP. The MIP was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. To analyze PA by the MIP/CNT-CP electrode, the electrode was incubated in the PA solution for a constant time and then, the anodic differential pulse voltammetry signal was recorded. Both extraction and electrochemical determination solutions were the same, making the procedure simple and fast. Presence of the CNT in the MIP electrode led to a great enhancement in the PA signal. The MIP material not only pre-concentrated PA at the electrode surface but also increased the electron-exchange rate. This was confirmed by electrochemical impedance spectroscopy. The effects of electrode composition, extraction condition, and voltammetry parameters on the sensing efficiency were optimized. Dynamic linear range, detection limit, and RSD of the sensor were estimated to be 0.1-200μM, 0.048μM (S/N), and 3.6% (n = 3), respectively. The utility of the method was confirmed by appropriate analysis results obtained for the determination of PA in the plasma and urine samples. Graphical Abstract.

Electrochemical Sensors for Heavy Metals Detection in Gracilaria corticata using Multiwalled Carbon Nanotubes Modified Glassy Carbon Electrode

Electrochemical methods for heavy metals detection have attracted considerable attention due to their simplicity, rapidity and high sensitivity. Voltammetric methods are a valid and very effective alternative for the simultaneous determination of heavy metals. An independent atomic absorption spectroscopic analysis of the seaweed sample was carried out and the results were compared with the World Health Organization permissible limits. The sample was clearly observed in the atomic force microscopic images, characterized by Fourier transform infrared spectroscopy and X-ray diffraction analysis. The electrochemical behavior of heavy metals on a bare glassy carbon electrode and a multiwalled carbon nanotubes modified glassy carbon electrode was studied by cyclic voltammetry, linear sweep anodic voltammetry, square wave anodic voltammetry and differential pulse anodic voltammetry. Very good responses were observed for all the metals when the modified electrode was employed.

Determination of Nitrite from Water Catchment Areas Using Graphite Based Electrodes

In this study, four electrodes based on unmodified graphite (G) and graphite modified with iron (II) phthalocyanine (Fe(II)Pc), nickel (II) phthalolocyanine (Ni(II)Pc) and Chitosan from crab shells (Ch) were compared and evaluated for determination of nitrites in different types of water samples using differential pulse anodic voltammetry. For the Ni(II)Pc modified graphite sensor, a high sensitivity (6.62 × 10−8 A mg L−1) and a lower quantification limit (0.0014 mg L−1) were obtained in comparison with G (sensitivity of 3.23 × 10−8 A mg L−1; LOD of 0.0040 mg L−1 and LOQ of 0.0046 mg L−1) and Fe(II)Pc/G (sensitivity of 3.13 × 10−8 A mg L−1; LOD of 0.0032 mg L−1 and LOQ of 0.0460 mg L−1). For the modified graphite microsensor based on Chitosan from crab shells a lower limit of detection (0.0002 mg L−1) and a lower limit of quantification (0.0005 mg L−1) were obtained. The unmodified graphite microsensor has a detection limit of 0.0040 mg L−1 for nitrite. These microsensors are indeed all suitable and reliable to employ for the assay of nitrite in different types of water samples from aquatic ecosystems in Romania with an RSD less that 0.11%.

Template- and Additive-free Electrosynthesis and Characterization of Spherical Gold Nanoparticles on Hydrophobic Conducting Polydimethylsiloxane.

Carbon-doped poly(dimethylsiloxane) (C-PDMS) modified with gold nanoparticles (AuNPs) is a highly promising material for the development of flexible lab-on-chip biosensors. Here, we present an electrochemical method to prepare stabilizer-free AuNPs directly on hydrophobic conducting substrates like C-PDMS without physical or chemical pre-treatment of the C-PDMS substrate. Using a potentiostatic triple pulse strategy, spherical, non-stabilized AuNPs of diameter 76±5 nm could be deposited within 5 s with narrow size-dispersion on the hydrophobic C-PDMS substrate in the absence of any structure directing or stabilizing agent. The detailed investigation of the mechanism of electrochemical formation of gold seeds and their three-dimensional growth on the hydrophobic surface along with nanomechanical atomic force-scanning electrochemical microscopy (QNM-AFM-SECM) characterization as well as conductive AFM allowed developing this fast electrochemical strategy with control in the desired size and size-dispersion of AuNPs. A detailed electrochemical investigation using cyclic voltammetry, anodic differential pulse voltammetry, and electrochemical impedance spectroscopy was conducted to characterize the electrochemical behavior of uncapped AuNPs deposited on C-PDMS. The Fc+ (MeOH)2 /Fc(MeOH)2 redox reaction at AuNPs-C-PDMS showed an improved charge transfer coefficient and heterogeneous charge transfer rate constant compared to the bare C-PDMS substrate.

Cyclic voltammetry behavior of tamoxifen in different electrolytes, electrochemical characterization, and its measurement by differential pulse anodic voltammetry

Cyclic voltammetry (CV) was performed on tamoxifen (tam) using different electrodes and in various acidic electrolytes containing 10% v v$^{-1}$ methanol (MeOH). Tam oxidation was found to be most favorable using 0.1 mol L$^{-1}$ H$_{2}$SO$_{4}$. To investigate the mechanism, we performed chronoamperometry, CV at different scan rates, differential pulse anodic voltammetry (DPAV), and electrochemical impedance spectroscopy on tam-covered glassy carbon electrodes (GCEs). The electrode area, diffusion coefficient, and surface concentration ($\Gamma )$ of tam were calculated to be 0.062 cm$^{2}$, 3.65 $\times $ 10$^{-6}$ cm$^{2}$ s$^{-1}$, and 3.2 $\times $ 10$^{-10}$ mol cm$^{-2}$ respectively. Then the effects of different parameters on the DPAV were optimized. The best conditions were 2.5% v v$^{-1}$ cMeOH, 0.1 mol L$^{-1}$ H$_{2}$SO$_{4}$, deposition potential 0.4 V, deposition time 30 s, and GCE rotating rate 400 rpm. Therefore, the calibration curve was plotted in the range of 0.5 to 5 $\mu $g mL$^{-1}$. The limits of detection and quantitation (LOD and LOQ) were found to be 0.008 and 0.025 $\mu $g mL$^{-1}$, respectively. The relative bias and standard deviation of 2 $\mu $g mL$^{-1}$ tam were estimated to be 5% (n = 5) and 2.3%, respectively. Finally, the proposed method was successfully employed for the determination of tam in real samples.

A new voltammetric sensor for sensitive and selective determination of xanthine based on DNA and polyaniline composite Langmuir–Blodgett film

DNA–polyaniline (PAn) complex Langmuir–Blodgett film modified glassy carbon electrode (GCE) was used as a new voltammetric sensor (DNA/PAn-LB/GCE) for xanthine (XA) detection. The characteristic of DNA/PAn-LB film was studied by electrochemical impedance spectroscopy and scanning electron microscope. Electrochemical behaviors of XA at the sensor were studied in pH 7.0 phosphate buffer solutions by cyclic voltammetry and differential pulse anodic voltammetry. The results showed that this new modified electrode exhibited an excellent immunity from uric acid and hypoxanthine interference and a new sensitive and selective electroanalytical method for XA was proposed with wider linear range. Under the optimum conditions, the calibration curve for XA was obtained over the range of 7.0×10−8–1.0×10−5molL−1, with the detection limit of 3.0×10−8molL−1. The practicability of this method was demonstrated by determining the concentration of XA in human serum samples.

A Glassy Carbon Electrode Modified with LangmuirBlodgett Film Composed of DNA and Polyaniline for the Sensitive Determination of Salbutamol

AbstractA composite LangmuirBlodgett film prepared from DNA and polyaniline was deposited on the surface of a glassy carbon electrode (GCE) to give a new voltammetric sensor for the β2‐agonist salbutamol (SAL). Cyclic voltammetry and electrochemical impedance spectroscopy were employed to study the characteristic of the modified electrode. The electrochemistry of SAL at the modified electrode was investigated at pH 6.8 by cyclic voltammetry and differential pulse anodic voltammetry. The oxidation of SAL at this electrode is an adsorption‐controlled irreversible process. A sensitive electroanalytical method for determination of SAL was worked out that displays high precision and good reproducibility. The method was applied to quantify SAL in tablets with satisfactory results.

Electrochemical behavior and analytical determination of Reactive Red 231 on glassy carbon electrode

The electrochemical behavior of the Reactive Red 231 has been investigated in phosphate buffer solutions by cyclic and differential pulse voltammetry on a glassy carbon electrode. The electrochemical oxidation of the dye exhibits two well-defined pH-dependent anodic peaks. The first one is quasi-reversible, while the second one at higher potential is irreversible process and mainly diffusion-controlled. The anodic oxidation properties of the dye in phosphate buffer at pH 3.77 allowed its sensitive determination at sub-micromolar levels by anodic differential-pulse voltammetry and presented a linear relationship from 0.25 μM to 200 μM. The reproducibility (at the 50 μM level) expressed in terms of relative standard deviation was 4.7% (for five determinations). A detection limit of 0.20 μM was achieved. The detection limit was around 50 times lower than that verified by spectrophotometric method. The applicability of the method was demonstrated by the determination of the dye in environmental water samples.

Electro‐oxidation and simultaneous determination of amlodipine and atorvastatin in commercial tablets using carbon nanotube modified electrode

Amlodipine besylate and atorvastatin calcium have been determined by the simultaneous voltammetric method at a multi-walled carbon nanotubes:graphite (MWCNTs:G) paste electrode. In comparison with a glassy carbon electrode, the prepared electrode showed an increase in the peak current because of the high electroactive surface area and excellent electronic conductivity of MWCNTs. The dependence of currents and potentials on pH were investigated for these components at the surface of the MWCNTs:G paste electrode. Differential pulse voltammetry was applied as a sensitive technique for simultaneous determination of the drugs in commercial tablets. By anodic differential pulse voltammetry, the calibration plot was linear in the range of 2.5-100 μg/ml with standard deviation between 2.7-7.1 and 1.8-8.3% for amlodipine and atorvastatin, respectively. The detection limit was 1 μg/ml at the prepared electrode in the buffered solution pH 6.

Investigation of tetrabromobisphenol A interacting with DNA nitrogen bases using experimental and density functional theory methods

The interactions of tetrabromobisphenol A (TBBPA) with the DNA nitrogen bases – guanine, adenine, thymine, and cytosine – were investigated, using ultraviolet–visible spectroscopy, cyclic voltammetry, anodic differential pulse voltammetry, and density functional theory simulation. Bonding constants of the TBBPA–DNA nitrogen base complexes were calculated. Global chemical reactivity descriptors including chemical potential, electronegativity, and electrophilicity indices were adopted to evaluate the chemical reactivity of TBBPA and DNA nitrogen bases. The condensed Fukui function was calculated to reveal reactive sites. The interaction energies between TBBPA and the nitrogen bases were also calculated. TBBPA interacted as an electrophile with guanine, adenine, and cytosine; with thymine, it served as a nucleophile. The interactions of TBBPA with the nitrogen bases followed the order: guanine > adenine > thymine > cytosine. The TBBPA–guanine complex exhibited the highest charge transfer, the largest bonding constant, and the most negative interaction energy.

Electrochemical determination of lead using bismuth modified glassy carbon electrode

Electrochemical application of bismuth film modified glassy carbon electrode was studied with the objective of lead detection. Bismuth film on glassy carbon substrate was formed in a plating solution of 2 mmol/L Bi(NO3)3, in 1 mol/L HCl at −1.1 V (vs. Ag/AgCl) for 300 s. Lead was detected by differential pulse anodic voltammetry in acetate buffer of pH 5.0 in the concentration range of 7.5 nmol/L to 12.5 μmol/L. Factors influencing the anodic stripping performance, including deposition time, solution pH, Bi(III) concentration, potential, pulse amplitude, pulse width, have been optimized. Three linear calibration plots in the range 7.5 nmol/L to 0.1 μmol/L, 0.25 to 1 μmol/L, 2.5 to 12.5 μmol/L with regression coefficients of 0.991, 0.986 and 0.978 respectively were obtained. The theoretical detection limit equivalent to three times standard deviation for 7.5 nmol/L lead (n = 5) was calculated to be 5.25 nmol/L utilizing a 5 min deposition time and sensitivity 83.97 A L/mol. The sensitivity and detection limit of the method was compared with reported voltammetric methods for detection of lead and the result obtained was found to be promising for determination of lead.

Nickel-ion detection on a boron-doped diamond electrode in acidic media

This work demonstrates the potential to assess Ni(II) concentration in neutral and acidic chloride environments on a boron-doped diamond electrode, without the introduction into the solution of an external chelating agent or markedly raising the pH. The nickel-ion quantification was achieved in solutions with pH values ranging from 8 to 4 using the electrochemical response associated with the Ni(II)/Ni(III) transition on a bare boron-doped diamond electrode. The associated electrochemical reaction was determined to be sensitive to the pH with a dependence relying on a proton stoichiometric number of 0.5 per mole of electrons. The detection protocol consisted of a reagentless electrodeposition of Ni in neutral or acidic solutions followed by oxidation to Ni(II) using differential pulse anodic voltammetry. This allowed the nickel-ion quantification with a limit of detection of 26.1μM and a linearity over the concentration interval from 10 to 500μM in a solution pH of 6.2. The regeneration of the pristine electrode surface was also achieved in the sample solution with an electropolishing treatment by holding the applied potential at +1.3V vs. Ag/AgCl for 30–240s, thus allowing a fast and efficient surface recovery.

Electrochemical detection of dihydromyricetin using a DNA immobilized ethylenediamine/polyglutamic modified electrode

A novel voltammetric sensor, based on DNA immobilized on the surface of an ethylenediamine/polyglutamic (En/PGA) modified glassy carbon electrode (GCE), was constructed and used for determination of dihydromyricetin (DMY). The electrochemical behaviour of DMY at this sensor was investigated in pH 3.6 NaAc-HAc buffer solutions by cyclic voltammetry (CV) and differential pulse anodic voltammetry (DPV). The oxidation of DMY is an adsorption-controlled irreversible process. The oxidation mechanism was proposed and discussed. It was found that the modified electrode exhibited a linear voltammetric response for DMY in the range of 4.0 × 10(-8) mol L(-1) to 2 × 10(-6) mol L(-1), with a detection limit of 2 × 10(-8) mol L(-1). The method was also applied successfully to detect DMY in an ampelopsis sample with satisfactory results.