Multiwall Carbon Nanotube Paste Electrode Research Articles

Electrochemical behavior of gatifloxacin at multi-walled carbon nanotube paste electrode and its interaction with DNA

The electrochemical oxidation of an antibacterial drug, gatifloxacin (GTF), at multi-walled carbon nanotube paste electrode was studied employing cyclic and differential pulse voltammetry methods. The effect of scan rate, pH, different electrolytes, pulse amplitude and accumulation time on electrochemical behavior of GTF were investigated. GTF shows a well-defined oxidation peak at +1.05 V in acetate buffer of pH 5.0±0.01. Under optimized conditions, the peak current is linear over the concentration range 2.13×10-5–1.7×10-4m with detection limit of 4.5×10-9m. The applicability of the proposed method is further extended to in vitro determination of the drug in biological fluids. Differential pulse voltammetry and UV-VIS absorption techniques were employed to probe the interaction between GTF and calf thymus DNA. The addition of ds-DNA to the analyte containing GTF results in a decrease of the peak current and a positive shift of the peak potential of GTF in differential pulse voltammetry analysis, indicating the dominance of the intercalating interaction. The spectroscopic data also confirm the interaction between GTF and ds-DNA. The combining constant (β) and combining number (m) of GTF-mDNA were also determined.

Voltammetric determination of homocysteine using multiwall carbon nanotube paste electrode in the presence of chlorpromazine as a mediator.

We propose chlorpromazine (CHP) as a new mediator for the rapid, sensitive, and highly selective voltammetric determination of homocysteine (Hcy) using multiwall carbon nanotube paste electrode (MWCNTPE). The experimental results showed that the carbon nanotube paste electrode has a highly electrocatalytic activity for the oxidation of Hcy in the presence of CHP as a mediator. Cyclic voltammetry, double potential step chronoamperometry, and square wave voltammetry (SWV) are used to investigate the suitability of CHP at the surface of MWCNTPE as a mediator for the electrocatalytic oxidation of Hcy in aqueous solutions. The kinetic parameters of the system, including electron transfer coefficient, and catalytic rate constant were also determined using the electrochemical approaches. In addition, SWV was used for quantitative analysis. SWV showed wide linear dynamic range (0.1–210.0 μM Hcy) with a detection limit of 0.08 μM Hcy. Finally, this method was also examined as a selective, simple, and precise electrochemical sensor for the determination of Hcy in real samples.

Multiwalled carbon nanotube paste electrode as an easy, inexpensive and highly selective sensor for voltammetric determination of Risperidone

A carbon paste electrode (CPE) modified with multi-walled carbon nanotube (MWCNT) was proposed for determination of Risperidone (Risp). The method was based on adsorptive accumulation of the Risp on to paste electrode, followed by reduction of the accumulated species by voltammetric scan. The parameters influencing the peak current were optimized. Under the optimum conditions, the electrode established linear response over a wide range of Risp concentrations (0.04 to 10 μmol L−1), the detection limit was 0.012 μmol L−1 (after 150 s accumulation). The method was applied to the determination of Risp in a pharmaceutical preparation and in human serum samples, and satisfactory results were obtained.

Fabrication of a new multi-walled carbon nanotube paste electrode for stripping voltammetric determination of Ag(i)

A new modified carbon paste electrode based on multi-walled carbon nanotubes and a synthesized Schiff base of N,N'-bis(2-hydroxybenzylidene)-2,2'(aminophenylthio) ethane, acting as a chelating agent for Ag(I) ions, is described. The electroanalytical procedure for the determination of Ag(I) was comprised of two steps: the chemical accumulation of the analyte under open-circuit conditions followed by replacing the medium with a 0.1 M HCl solution where the accumulated Ag(I) was reduced for 20 s in -0.7 V. The potential was then scanned from -0.2 to +0.2 V to obtain the voltammetric peak. The effective parameters in the sensor response were examined. Under optimized operational conditions, a linear response range from 0.5-200 ng mL(-1) was obtained. The detection limit for silver determination was 0.092 ng mL(-1). For 7 successive determinations of 15.0 and 60.0 ng mL(-1) of Ag(I), relative standard deviations of 2.2% and 1.2% were obtained, respectively. The procedure was applied in determining Ag(I) in X-ray photographic films and water samples.

Modified carbon nanotube paste electrode for voltammetric determination of carbidopa, folic Acid, and tryptophan.

A simple and convenient method is described for voltammetric determination of carbidopa (CD), based on its electrochemical oxidation at a modified multiwall carbon nanotube paste electrode. Under optimized conditions, the proposed method exhibited acceptable analytical performances in terms of linearity (over the concentration range from 0.1 to 700.0 μM), detection limit (65.0 nM), and reproducibility (RSD = 2.5%) for a solution containing CD. Also, square wave voltammetry (SWV) was used for simultaneous determination of CD, folic acid (FA), and tryptophan (TRP) at the modified electrode. To further validate its possible application, the method was used for the quantification of CD, FA, and TRP in urine samples.

Determination of ascorbic acid by a modified multiwall carbon nanotube paste electrode using cetrimonium iodide/iodine

A new modified graphite-multiwall carbon nanotube paste electrode for the determination of ascorbic acid (AA) based on cetrimonium iodide-iodine is described. The electrochemical response characteristics of the modified electrode toward AA were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in phosphate buffer solution (pH 2.0). When compared to activated carbon, graphite, and multiwall carbon nanotube paste electrode containing new modifier, the proposed modified paste electrode not only shifted the oxidation potential of AA towards less positive potential but also enhanced its oxidation peak current. Further, the oxidation of AA was highly stable at the modified paste electrode. The optimum analytical conditions were sought. The current response of AA increases linearly while increasing its concentration from 5.6 \times 10^{-5} to 1.2 \times 10^{-2} M with the correlation coefficient of 0.999 and a detection limit (3\sigma) was found to be 1.2 \times 10^{-6} M. The present modified paste electrode was also successfully used for the determination of AA in the presence of common interference compounds. The present modified electrode was successfully used in the determination of AA in pharmaceutical and food samples.

Simultaneous determination of cysteamine and folic acid in pharmaceutical and biological samples using modified multiwall carbon nanotube paste electrode

A carbon paste electrode (CPE) chemically modified with multiwall carbon nanotubes and ferrocene (FC) was used as a selective electrochemical sensor for the simultaneous determination of trace amounts of cysteamine (CA) and folic acid (FA). This modified electrode showed very efficient electrocatalytic activity for the anodic oxidation of CA. The peak current of differential pulse voltammograms of CA and FA increased linearly with their concentration in the ranges of 0.7–200 μmol/L CA and 5.0–700 μmol/L FA. The detection limits for CA and FA were 0.3 μmol/L and 2.0 μmol/L, respectively. The diffusion coefficient (D) and transfer coefficient (α) of CA were also determined. These conditions are sufficient to allow determination of CA and FA both individually and simultaneously.

Highly improved electrooxidation of formaldehyde on nickel/poly ( o-toluidine)/Triton X-100 film modified carbon nanotube paste electrode

In present work, o-toluidine (OT) monomer is electropolymerized in the presence of an aqueous acidic solution containing Triton X-100 (TX-100) non-ionic surfactant onto multi-walled carbon nanotube paste electrode (CNTPE). The as-prepared substrate is used as a porous matrix for dispersion of Ni (II) ions by immersing the modified electrode in a nickel (II) sulfate solution. The modified electrodes are characterized by field emission scanning electron microscopy (FE-SEM) and electrochemical methods. The electrochemical characterization of the nickel/poly ( o-toluidine)/Triton X-100 film modified carbon nanotube paste electrode (Ni/POT (TX-100)/MCNTPE) exhibits redox behavior of Ni(III)/Ni(II) couple in alkaline medium. It has been shown that POT/TX-100 film at surface of the CNTPE improves efficiency of the catalyst toward formaldehyde electrooxidation. Moreover, the effects of various parameters such as TX-100 concentration, formaldehyde concentration, OT concentration, film thickness and accumulation time on the electrooxidation of formaldehyde as well as long-term stability of the Ni/POT (TX-100)/MCNTPE have also been investigated.

Preparation of Tetraheptylammonium Iodide-Iodine Graphite-Multiwall Carbon Nanotube Paste Electrode: Electrocatalytic Determination of Ascorbic Acid in Pharmaceuticals and Foods

The present work describes the construction of a new modified graphite-multiwall carbon nanotube paste electrode by casting the appropriate mixture of tetraheptylammonium iodide-iodine as a new modifier. The modified paste electrode was used for the determination of ascorbic acid (AA) in a phosphate buffer solution (pH 2.0). When compared to activated carbon, a graphite and multiwall carbon nanotube paste electrode containing a new modifier, the proposed modified paste electrode not only shifted the oxidation potential of AA towards a less-positive potential but also enhanced its oxidation peak current. Further, the oxidation of AA was highly stable at the modified paste electrode. The optimum analytical conditions were sought. The current response of AA increases linearly while increasing its concentration from 5.6 × 10(-5) to 1.2 × 10(-2) M with a correlation coefficient of 0.9991; the detection limit (3σ) was found to be of 3.6 × 10(-5) M. The present modified paste electrode was also successfully used for the determination of AA in the presence of common interference compounds. The present modified electrode was successfully demonstrated towards the determination of AA in pharmaceutical and food samples.

Adsorptive stripping voltammetric determination of podophyllotoxin, an antitumour herbal drug, at multi-walled carbon nanotube paste electrode

Adsorption stripping voltammetry, a very sensitive electroanalytical method, was employed to determine podophyllotoxin, a kind of antitumour herbal drug at a multi-wall carbon nanotube (MWCNT)-modified carbon paste electrode (CPE) surface. In the following anodic sweep from 0.5 to 1.5 V, podophyllotoxin, adsorbed at the MWCNT-modified CPE surface, was oxidized and yielded a sensitive oxidation peak with E1/2/Ep approximately 1.16 V/1.18 V over the scan rates of 10–120 mV s−1. From CV and SWV studies of podophyllotoxin in the acetate buffers of various pH values, it was found that protons were involved in the oxidation of the drug at the H+/e− ratio of one (∆Ep/pH = 56 mV at 25 °C). Its electrochemical behaviour was irreversible. The experimental conditions, such as supporting electrolyte, pH value, accumulation time, ionic strength and scan rate, were optimized for the measurement of podophyllotoxin. The best results were obtained in 0.02 M acetate/acetic acid buffer (pH 4.6) containing 0.04 M KCl (1:49, v/v) for 60 s accumulation. The oxidation peak current varies linearly with the concentration of podophyllotoxin over the range of 199–1796 pg mL−1. The limits of detection and quantification of the pure drug are 4.5 and 14.96 pg mL−1, with the correlation coefficient, r = 0.998 and the relative standard deviation, RSD = 1.3% (n = 5). This new method was successfully applied to the determination of podophyllotoxin in a plant sample of the rhizome of Podophyllum hexandrum. Recoveries were 99.173–101.231%. The relative standard deviations of intraday and interday analyses for podophyllotoxin were 0.55 and 0.61%, respectively (n = 3).

Electrochemical determination of a hemorheologic drug, pentoxifylline at a multi-walled carbon nanotube paste electrode

The electrochemical oxidation of a hemorheologic drug, pentoxifylline was investigated at a multi-walled carbon nanotubes-paraffin oil paste electrode using cyclic and differential pulse voltammetry. The oxidation process was irreversible over the pH range studied and exhibited an adsorption-controlled behavior. All experimental parameters have been optimized. Under the optimum conditions, the oxidation peak current was linearly proportional to the concentration of pentoxifylline in the range of 3.0 × 10 − 5 to 2.0 × 10 − 4 M with a detection limit of 1.69 × 10 − 7 M by differential pulse voltammetry with 180 s accumulation. The proposed method was successfully applied to pentoxifylline determination in pharmaceutical and urine samples. Satisfactory recoveries of the analyte from the real samples and a good agreement between the concentration ranges studied and the real ranges encountered in the urine samples, when treated with the drug make the developed method applicable in clinical analysis. This method can also be employed in quality control and routine determination of drugs in pharmaceutical formulations.

Simultaneous voltammetric determination of Brilliant Blue and Tartrazine in real samples at the surface of a multi-walled carbon nanotube paste electrode

A carbon paste electrode (CPE) chemically modified with multi walled carbon nanotubes (MWCNTs) was used for the sensitive and selective determination of Brilliant Blue (BB) and Tartrazine (Tz) by voltammetric methods such as cyclic, differential pulse and square wave voltammetry (CV, DPV, and SWV), and chronoamperometry (CHA). The peak current increased linearly with the BB concentration within the concentration range of 0.05 to 22.0 μmol l−1 for DPV and from 0.05 to 25.0 μmol l−1 for SWV. The detection limits (S/N > 3) for BB by DPV and SWV were found to be 9.0 and 5.0 nmol l−1, respectively. Results of CV showed two well-resolved anodic waves with the peak separation approximately 200 mV for the electrochemical oxidation of BB and Tz, which makes it possible for simultaneous determination of both compounds. The treatment of the CV data showed that the redox of BB and Tz was reversible diffusion-controlled and totally irreversible reactions, respectively. The diffusion coefficient (D/cm2 s−1 = 2.8 × 10−5) for BB was determined using chronoamperometry. DPV method was applied for the quantitative determination of BB and Tz. High sensitivity and selectivity, low detection limit (nanomolar), good reproducibility, easy preparation and regeneration of the electrode make it very suitable for the determination of BB and Tz in soft drinks.

Molecularly imprinted-multiwall carbon nanotube paste electrode as a biosensor for voltammetric detection of rutin

A new molecularly imprinted polymer–multiwall carbon nanotube paste electrode (MIP–MWNPE) was prepared as a voltammetric sensor for rutin. The electrochemical behavior of rutin at the surface of the modified electrode was studied using cyclic voltammetry (CV) and square wave voltammetry (SWV). Under the optimized conditions, the oxidation peak current of rutin showed two linear dynamic ranges (0.08–1.4 μM and 2.0–160.0 μM) with a detection limit of 0.05 μM, using square wave voltammetric method. The RSD% for 5.0 and 10.0 μM determination of rutin were 2.7% and 2.9%, respectively. The kinetic parameters such as electron transfer coefficient (α) and charge transfer rate constant (ks/s−1) were also determined using the electrochemical approach. The modified electrode showed good sensitivity, special selectivity, and stability for rutin analysis. It was successfully applied for the determination of rutin in real samples such as urine and pharmaceutical formulation with satisfactory results.

Electrochemical fabrication of novel Pt/poly ( m-toluidine)/Triton X-100 composite catalyst at the surface of carbon nanotube paste electrode and its application for methanol oxidation

In this work, for the first time an aqueous solution of Triton X-100 (TX-100) non-ionic surfactant is used as an additive for electropolymerization of m-toluidine (MT) onto multi-walled carbon nanotube paste electrode (CNTPE), which is investigated as a novel matrix for dispersion of platinum particles. Electrochemical response of the poly ( m-toluidine) film prepared in the presence of TX-100 (PMT/TX-100) is, at least, 20 times higher than that obtained in the absence of the surfactant. The as-prepared substrate is used as porous matrix for dispersion of platinum particles by potentiodynamic method. As-formed novel support and composite catalyst are characterized by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), and electrochemical methods. The SEM images reveal that the deposits are composed of spherical Pt particles. The EDS confirms the presence of Pt on the modified electrode. The electrochemical methanol oxidation reaction (MOR) is studied at the surface of this modified electrode. It has been shown that the PMT/TX-100 at the surface of CNTPE improves the catalytic efficiency of the deposited platinum particles toward MOR. Then, the influence of scan rates of potential and switching potential on the MOR as well as long-term stability of this modified electrode have been investigated by chronoamperometric and cyclic voltammetric methods.

A novel, effective and low cost catalyst for methanol oxidation based on nickel ions dispersed onto poly( o-toluidine)/Triton X-100 film at the surface of multi-walled carbon nanotube paste electrode

In this work, for the first time an aqueous solution of Triton X-100 (TX-100) [t-octyl phenoxy polyethoxy ethanol] non-ionic surfactant is used as an additive for electropolymerization of o-toluidine (OT) onto multi-walled carbon nanotube paste electrode (CNTPE), which is investigated as a novel matrix for dispersion of nickel ions. The growth of polymeric film in the absence of TX-100 is poor, while it considerably increases in the presence of the surfactant and its growth is continued up to 60th cycle. The as-prepared substrate is used as porous matrix for dispersion of transition metal ions of Ni(II) to POT/TX-100 film by immersing the modified electrode in a 0.1 M nickel sulfate solution. The electrochemical characterization of this modified electrode exhibits redox behavior of Ni(III)/Ni(II) couple. It has been shown that POT/TX-100 at the surface of CNTPE improves catalytic efficiency of the dispersed nickel ions toward methanol oxidation. Then, using a chronoamperometric method, the catalytic rate constant, k, for methanol oxidation is found to be 7.40 × 10 4 cm 3 mol −1 s −1. At the end of this work, long-term stability of this modified electrode has been investigated.

Electrocatalytic oxidation of hydroxylamine at Ni(II)-morin complex modified carbon nanotube paste electrode

A modified electrode, nickel(II)-morin complex modified multi-wall carbon nanotube paste electrode (Ni(II)-MR-MWCNT-PE), has been fabricated by electrodepositing Ni(II)-MR complex on the surface of MWCNT-PE in alkaline solution. The Ni(II)-MR-MWCNT-PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple compared with Ni(II)-MR complex modified carbon paste electrode (CPE). It also shows better electrocatalytic activity toward the oxidation of hydroxylamine than the Ni(II) modified MWCNT-PE (Ni(II)-MWCNT-PE) and Ni(II)-MR-CPE. Kinetic parameters such as the electron transfer coefficient α, rate constant k s of the electrode reaction and the catalytic rate constant k cat of the catalytic reaction are determined. Moreover, the catalytic currents present linear dependence on the concentration of hydroxylamine from 2.5 × 10−6 to 4.0 × 10−4 mol L−1 by amperometry. The detection limit and sensitivity are 8.0 × 10−7 mol L−1 and 56.2 mA L mol−1, respectively. The modified electrode for hydroxylamine determination is of the property of simple preparation, good stability, fast response and high sensitivity.

Simultaneous voltammetric determination of acetaminophen, aspirin and caffeine using an in situ surfactant-modified multiwalled carbon nanotube paste electrode

A carbon nanotube paste electrode modified in situ with Triton X 100 was developed for the individual and simultaneous determination of acetaminophen (ACOP), aspirin (ASA) and caffeine (CF). The electrochemical behavior of these three molecules was investigated employing cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronocoulometry (CC) and adsorptive stripping differential pulse voltammetry (AdSDPV). Kramers–Kronig transformation implied that the resulting impedance data were validated and were of very good quality. These studies revealed that the oxidation of ACOP, ASA and CF is facilitated at an in situ surfactant-modified multiwalled carbon nanotube paste electrode (ISSM-CNT-PE). After optimization of analytical conditions employing this electrode at pH 7.0 in phosphate buffer (0.1 M), the peak currents for the three molecules were found to vary linearly with their concentrations in the range of 2.91 × 10 −7–6.27 × 10 −5 M with detection limits of 2.58 × 10 −8, 8.47 × 10 −8 and 8.83 × 10 −8 M for ACOP, ASA and CF respectively using AdSDPV. The prepared modified electrode showed several advantages, such as a simple preparation method, high sensitivity, very low detection limits and excellent reproducibility. Furthermore, the proposed method was employed for the simultaneous determination of ACOP, ASA and CF in pharmaceutical formulations, urine and blood serum samples and the obtained results were found to be satisfactory.

Simultaneous Determination of Ascorbic Acid and Uric Acid by a New Modified Carbon Nanotube-Paste Electrode Using Chloromercuriferrocene

The electrochemical behavior of ascorbic acid (AA) and uric acid (UA) at the surface of a multiwall carbon nanotube-paste electrode (MCNTPE) modified with incorporate chloromercuriferrocene (CMF) was investigated. The voltammetric studies using the MCNTPE/CMF electrode show two well-resolved anodic peaks for AA and UA with a potential difference of 430 mV, revealing the possibility of the simultaneous electrochemical detection of these compounds. The optimum analytical conditions were sought. Linear calibration plots were obtained over the range of 8.0 x 10(-6)-6.9 x 10(-4) M and 2.4 x 10(-6)-6.9 x 10(-4) M with detection limits (3sigma) of 2.6 x 10(-6) and 7.9 x 10(-7) M for AA and UA, respectively. The electrode with the best conditions is applied for selective determination of AA and UA in complex biological and clinical matrices.

Amperometric immunosensor for ricin by using on graphite and carbon nanotube paste electrodes

Ricin is a scheduled chemical warfare agent and biological warfare agent. Attempts were made for the detection of ricin in water samples by utilizing amperometric immunosensors. These electrodes were made by mixing Paraffin oil with graphite powder and multiwalled carbon nanotubes. The graphite paste electrode (CPE) and multiwalled carbon nanotubes paste electrode (MWCNTPE) were tested for their ability to detect 1-naphthol. A sandwich enzyme linked immunosorbent assay system was used to detect ricin. The detection limit for both electrodes was compared. It was found that the response of amperometric sensor is proportional to the ricin concentration in both the cases and is linear in the range 0.625-25 ng/ml for MWCNTPE and 2.5-25 ng/ml for CPE. The SEM showed that the MWCNTPE has revealed crevices/voids in which the antibodies may get trapped. Spectroscopic experiments proved that MWCNTPE adsorbs antibodies better than CPE. The high sensitivity of MWCNTPE was attributed to its better electrochemical properties rather than to its efficiency to adsorb antibodies.

Nickel(II)–baicalein complex modified multiwall carbon nanotube paste electrode and its electrocatalytic oxidation toward glycine

A modified electrode, nickel(II)–baicalein complex modified multiwall carbon nanotube paste electrode (Ni(II)–BA–MWCNT–PE), has been fabricated by electrodepositing Ni(II)–BA complex on the surface of MWCNT–PE in alkaline solution. The Ni(II)–BA–MWCNT–PE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple compared with Ni(II)–BA–carbon paste electrode (CPE). It also shows better electrocatalytic activity toward the oxidation of glycine than Ni(II)–MWCNT–PE. Kinetic parameters such as the electron transfer coefficient α, rate constant k s of the electrode reaction, the diffusion coefficient D of glycine, and the catalytic rate constant k cat of the catalytic reaction are determined. Moreover, the catalytic currents present linear dependence on the concentration of glycine from 20 μM to 1.0 mM by amperometry. The detection limit and sensitivity are 9.2 μM and 3.92 μA mM −1, respectively. The modified electrode for glycine determination is of the property of simple preparation, fast response, and good stability.