Carbon Nanotube Paste Electrode Research Articles

Benzoylferrocene-modified carbon nanotubes paste electrode as a voltammetric sensor for determination of hydrochlorothiazide in pharmaceutical and biological samples

The electrooxidation of hydrochlorothiazide (HCT) at the surface of a benzoylferrocene modified multi-walled carbon nanotube paste electrode was studied using electrochemical approaches. Under the optimized conditions (pH 7.0), the square wave voltammetric peak current of HCT increased linearly with HCT concentration in the ranges of 6.0 × 10−7 to 3.0 × 10−4 M. The detection limit was 9.0 × 10−8 M HCT. The diffusion coefficient (D = 1.75 × 10−5 cm2/s) and electron transfer coefficient (α = 0.45) for HCT oxidation were also determined. The proposed sensor was successfully applied for the determination of HCT in human urine and tablet samples.

Carbon paste electrode incorporating multi-walled carbon nanotube/ferrocene as a sensor for the electroanalytical determination of N-acetyl-L-cysteine in the presence of tryptophan

The preparation and electrochemical performance of the carbon nanotube paste electrode modified with ferrocene (FCMCNPE) was investigated for electrocatalytic behaviour toward oxidation of N-acetyl-L-cysteine (NAC) in the presence of tryptophan (Trp) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results showed an efficient electrocatalytic activity of FCMCNPE toward oxidation of NAC and Trp, as the electrooxidation of NAC and Trp together gave two well-defined anodic peaks, revealing the applicability of this modified electrode for simultaneous voltammetric detection of mentioned compounds in the same solution. The values of catalytic rate constant (k) and the apparent diffusion coefficient (Dapp) were also calculated using chronoamperometry. The DPV method was applied as a sensitive method for the quantitative detection of trace amounts of NAC and Trp. A linear dynamic range from 1.0 to 18.0 $\upmu $ M for NAC and 2.0 to 150.0 $\upmu $ M for Trp was obtained using DPV method in pH 7.00 buffered solution and the detection limit (3σ) was determined as 0.49 $\upmu $ M and 0.54 $\upmu $ M for NAC and Trp, respectively. The proposed method was also applied for analysis of NAC tablet, investigating the applicability of the proposed voltammetric method for determination of NAC in real sample.

Evaluation of antioxidant activity of crocin, podophyllotoxin and kaempferol by chemical, biochemical and electrochemical assays

The present study was designed to evaluate the antioxidant potential of three natural origin drugs, namely crocin, kaempferol and podophyllotoxin by chemical, biochemical and electrochemical assays. The chemical assay was carried out by DPPH and reducing power assays while the biochemical assay evaluated the lipid peroxidation inhibition capacity, using brain cells as models; the electrochemical characterization was performed by cyclic voltammetry and differential pulse voltammetry using multi-walled carbon nanotube paste electrode (MWCNTPE) in 0.02M acetate buffer (pH 4.5). The superoxide radical scavenging activity was performed at dropping mercury electrode (DME) in 0.1M KCl. All the species proved to have antioxidant activity, and particularly, by the electrochemical techniques, it has been shown that these drugs showed scavenging ability on superoxide anion produced by electrochemical reduction of oxygen. The highest scavenging property of crocin may be due to the hydroxyl and glucose moieties that could provide the necessary component as a radical scavenger.

Voltammetric method optimized by multi-response assays for the simultaneous measurements of uric acid and acetaminophen in urine in the presence of surfactant using MWCNT paste electrode

In the present study, an electroanalytical method for the simultaneous determination of acetaminophen (AC) and uric acid (UA) in urine samples with a carbon nanotube paste electrode (CNTPE) employing a cationic surfactant (cetylpyridinium bromide, CPB) was developed. The optimization of the proposed differential pulse voltammetric method was performed by means of multi-response assays, highly recommended for simultaneous analysis. Under optimized conditions (pH 7.7, phosphate concentration of 0.1molL−1, pulse amplitude of 123mV, modulation time of 5ms, CPB concentration of 0.30mmolL−1 and scan rate of 100mVs−1), a remarkable peak separation of UA and AC at 174mV was achieved. The linear curves for the simultaneous determination of UA and AC were built in concentration range of 5.0–92.6μmolL−1 with satisfactory regression of 0.995 for UA and 0.999 for AC. Limits of detection were found to be 0.25 and 0.57μmolL−1 for UA and AC, respectively, and the precision assessed as relative standard deviation (RSD) for ten determinations was found to be 3.20% and 1.34% for respective concentrations of 10.0 and 72.5μmolL−1 for UA and 4.3% and 1.6% for AC. The electrochemical sensor with anti-fouling features was successfully applied for the free-interference simultaneous determination of UA and AC in urine samples.

Electrochemical Behaviour of a Modified Carbon Nanotube Paste Electrode and Its Application for Simultaneous Determination of Epinephrine, Uric Acid and Folic Acid

Electrochemical Behaviour of a Modified Carbon Nanotube Paste Electrode and Its Application for Simultaneous Determination of Epinephrine, Uric Acid and Folic Acid

Square wave voltammetric determination of methiocarb insecticide based on multiwall carbon nanotube paste electrode

Cyclic voltammogram of methiocarb in 0.1 M H2SO4 exhibited an irreversible anodic peak at about +1285 mV versus Ag/AgCl. Electro-oxidation and determination of methiocarb in spiked soil, river water and agrochemical formulation were realized on a newly prepared carbon-nanotube paste electrode by applying square wave voltammetry (SWV). The dE p /dpH value indicated that the oxidation mechanism involved the coupling of H+ with the oxidation process. The peak signals were linearly related to methiocarb concentration in the range of 1.5–59.1 mgL−1 with a detection limit of 0.45 mgL−1. The accuracy and selectivity of the proposed method were shown by calculating the recoveries of methiocarb from soil, river water and pesticide formulation Mesurol®. The calculated percent recoveries for soil and river water samples spiked with 30.0 μg g−1 and 40.0 μg mL−1 levels were 99.3 ± 1.2 and 98.5 ± 0.3 at 95 % confidence limit, respectively.

Catalytic Voltammetric Determination of Vanadium in Crude Oil at Carbon Nanotube Paste Electrode

A catalytic voltammetric method for the determination of vanadium(V) at a multi-wall carbon nanotube paste electrode (MWCNT-PE) in a 4-(2-pyridylazo)-resorcinol(PAR)-bromate system is proposed. The voltammetric response of V(V)-PAR complex at MWCNT-PE was significantly enhanced because of a catalytic cycle consisting of electrochemical reduction of V(V) ion in the complex and subsequent chemical oxidation of the reduction product of V(V) by bromate. In pH 2.70 H2SO4 solution containing 5.0×10-6 mol•L-1 PAR and 3.0×10-2 mol•L-1 KBrO3 without any preconcentration, the linear sweep voltammetric peak current of the catalytic wave was proportional to the vanadium concentration in the range of 8.0×10-9 to 3.0×10-6 mol•L-1. The detection limit was 2.5×10-9 mol•L-1. Using the proposed method, the vanadium concentration in crude oil was evaluated and the results were compared with those of atomic absorption spectrometry.

Electrochemical behavior of dopamine at a [1,1′-binaphthalene]-4,4′-diol-modified carbon nanotube paste electrode and the simultaneous determination of dopamine, folic acid and uric acid

The electro-oxidation of dopamine (DA), uric acid (UA), folic acid (FA), and their mixture has been studied using a modified carbon nanotube paste electrode of [1,1′-binaphthalene]-4,4′-diol (BND) using cyclic voltammetry, chronoamperometry and differential pulse voltammetry. The electrocatalytic process was greatly dependent on the pH of the supporting electrolyte. This modified electrode was quite effective, not only in the detection of DA, UA and FA but also in the simultaneous determination of these species in a mixture. The catalytic peak current obtained was linearly dependent on the DA, UA and FA concentrations in the range of 5.0–600.0 μM, 6.5–752.0 μM and 9.5–1128.0 μM, respectively, and the detection limits for DA, UA and FA were 0.49, 4.28 and 7.69 μM, respectively. The diffusion coefficient (D/cm2 s−1 = 6.8 × 10−6) and the kinetic parameters such as the catalytic rate constant (k/M−1 s−1 = 18.22 × 103) and the electron transfer coefficient (α = 0.36) for DA were determined using electrochemical approaches.

Osmium-Polymer Modified Carbon Nanotube Paste Electrode for Detection of Sucrose and Fructose

The aim of the work was the modification of a carbon nanotube paste electrode with a highly original osmium-polymer hydrogel for the development of a new amperometric biosensor for detection of sucrose and fructose. The biosensor for sucrose is based on the activity of the enzymes invertase and fructose dehydrogenase (FDH) immobilized into a carbon nanotube paste (CNTP) electrode properly modified with the Os-polymer. A second biosensor, for fructose only, is constructed containing inactive invertase and used for detection of fructose and for signal subtraction. The biosensors exhibit a detection limit for sucrose of 2 mM and for fructose of 1 mM, linearity up to 5 mM for both biosensors, high sensitivity (1.98 mA·cm-2·mM for sucrose and 1.95 mA·cm-2·mM for fructose), a good reproducibility (RSD = 2.5% for sucrose and 2.1% for fructose), fast response time (8 s for sucrose and 4 s for fructose) and a stability of about 4 months for both biosensors when stored under wet conditions at 4°C. Finally, the biosensors were applied for specific determination of sucrose and fructose in several commercial fruit juice samples and validated with a commercial spectrophotometric enzymatic kit.

Electrocatalytic determination of cysteamine using multiwall carbon nanotube paste electrode in the presence of 3,4-dihydroxycinnamic acid as a homogeneous mediator

The electrooxidation of cysteamine (CA) was studied by modified carbon nanotubes paste electrode in the presence of 3,4-dihydroxycinnamic acid (3,4-DHCA) using cyclic voltammetry, chronoamperometry and linear sweep voltammetry. Using the modified electrode, the kinetics of CA electrooxidation was considerably enhanced by lowering the anodic over-potential through a catalytic fashion. The mechanism of CA electrochemical behavior at the modified electrode surface was analyzed by various electrochemical methods in the presence of mediator. The prepared modified electrode showed voltammetric responses with high sensitivity for CA, making it very suitable for the detection of CA at trace levels. A linear dynamic range of 0.25-400 µmol L-1 for CA was obtained in buffered solutions with pH 7.0. The limit of detection was 0.09 µmol L-1.

Electrooxidation and determination of methacetin (p-acetanisidide) by square wave voltammetry using multiwalled carbon nanotube electrode

A multiwall carbon nanotube paste electrode (MWCNTPE) was fabricated to investigate the detailed electrochemical behavior of methacetin and achieve its sensitive electroanalytical determination. The sensitive and selective square wave anodic peak seen at +1.06 V was linearly related to methacetin concentration in the range of 0.11 to 22.3 mg L−1 [0.665 to 135 μM]. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.032 mg L−1 [0.193 μM] and 0.11 mg L−1 [0.665 μM], respectively. The percentage recovery of methacetin calculated from natural lake water samples spiked at the 5.0 μg mL−1 [30.3 μM] level was 94.2% with a relative standard deviation of 0.21%. The considerably high recoveries and low standard deviations were evidence for the high accuracy and precision of the recommended method. The recovery of 10.0 μg mL−1 [60.5 μM] methacetin in the presence of the same concentrations of other pesticides such as benzanilide, propanil, tribenuron methyl, rimsulfuron, metsulfuron methyl and chlorsulphuron ranged from 89.2% to 98.3%. The oxidation peak of 10 mg L−1 [65.3 μM] dopamine appeared at +0.740 V(vs. Ag/AgCl) and did not display a significant interfering effect, therefore methacetin and dopamine could be simultaneously determined.

Nano-Structured Ni(II)–Baicalein Modified Multiwall Carbon Nanotube Paste Electrode for the Electrocatalytic Oxidation of Hydroxylamine

A nano-structured Ni(II)–baicalein(BA) film is electrodeposited on a multiwall carbon nanotube paste electrode in alkaline solution. The modified electrode shows electrocatalytic activity toward the oxidation of hydroxylamine. Kinetic parameters such as the electron transfer coefficient α, rate constant ks of the electrode reaction and the catalytic rate constant kcat of the catalytic reaction are determined. The catalytic currents present linear dependence on the concentration of hydroxylamine from 2.5×10-6 mol•L-1 to 4.0×10-4 mol•L-1 by amperometry. The detection limit and sensitivity are 6.0×10-7 mol•L-1 and 31.2 mA•L•mol-1, respectively. The modified electrode has been applied to determine hydroxylamine in water samples with satisfactory results.

Adsorptive stripping voltammetric study of vitamin B1 at multi-walled carbon nanotube paste electrode

The electrochemical response of vitamin B1 at different types of carbon electrodes viz: glassy carbon electrode (GCE), carbon paste electrode (CPE), single walled carbon nanotube paste electrode (SWCNTPE) and multi walled carbon nanotube paste electrode (MWCNTPE) has been investigated using cyclic voltammetric (CV) and differential pulse adsorptive stripping voltammetric (DPAdSV) methods. A simple and selective differential pulse adsorptive stripping voltammetric method has been developed for the determination of vitamin B1 in pure form and in pharmaceutical preparations. Various parameters that can influence the peak signal (effect of buffer, accumulation time, pH, scan rate, accumulation potential, and pulse amplitude) have been scrutinized. The best results were obtained in acetate buffer (pH 6.3) using multi-walled carbon nanotube paste electrode at a deposition time of 80s, deposition potential of 0.0V, scan rate of 50mVs−1 and pulse amplitude of 50mV.The reduction peak current varies linearly with the concentration of vitamin B1 over the range of 1.0×10−7–1.0×10−6M. The limits of detection and quantification of the pure drug are 1.1×10−10M and 2.0×10−9M, with the correlation coefficient, r=0.997 and the relative standard deviation, RSD=1.2% (n=5). Experimental results reveal that the MWCNTPE has advantages of small background current, high signal to background current ratio and good reproducibility.

Electrochemical study of dsDNA on carbon nanotubes paste electrodes applying cyclic and differential pulse voltammetry

Abstract Abstract Carbon nanotubes paste electrodes (CNTPEs) in combination with adsorptive transfer stripping voltammetry are shown to be very suitable for the determination of calf thymus double-stranded DNA (dsDNA). The performance of three types of multi-walled carbon nanotubes paste electrodes (MWCNTPEs) is investigated. The effects of surface pre-treatment and accumulation conditions on the adsorption and electrooxidation of the dsDNA at MWCNTPEs are also described. The results indicate that the electroactivity inherent to carbon nanotubes/paste electrodes allows a large enhancement of the guanine oxidation signal compared to that obtained at the conventional carbon paste electrodes (CPEs). Moreover, the extent of the enhancement dependents on the type of MWCNTs incorporated into the paste. Based on the signal of guanine, under optimal conditions, very low levels of dsDNA can be detected following short accumulation times for all three types of MWCNTPEs (MWCNTPE1, MWCNTPE2, MWCNTPE3), with detection limits of 2.64 mg L−1, 2.02 mg L−1 and 1.46 mg L−1, respectively. Additionally, the dsDNA isolated from rat liver tissues is determined by use of the previously mentioned MWCNTPEs. Graphical abstract

A new strategy for the selective determination of glutathione in the presence of nicotinamide adenine dinucleotide (NADH) using a novel modified carbon nanotube paste electrode

A novel electrochemical sensor for the simultaneous determination of glutathione (GSH) and nicotinamide adenine dinucleotide (NADH) is described. The sensor is based on a carbon paste electrode (CPE) modified with benzamide derivative and multiwall carbon nanotubes. This mixture makes a modified electrode that is sensitive for the electrochemical detection of these compounds. Under optimum conditions and at pH 7.0, oxidation of GSH occurs at a potential of about 330mV less positive than that at an unmodified CPE. The voltammetric peak currents are linearly dependent on GSH and NADH concentrations in the ranges 0.09–300μmolL−1 GSH and 5.0–600μmolL−1 NADH. The detection limits found for GSH and NADH were 0.05μmolL−1 and 1.0μmolL−1, respectively. The electrochemical sensor was also used for the determination of GSH in urine, pharmaceutical and hemolysed erythrocyte samples.

Biosensor based on multi-walled carbon nanotubes paste electrode modified with laccase for pirimicarb pesticide quantification

This study focused on the development of a sensitive enzymatic biosensor for the determination of pirimicarb pesticide based on the immobilization of laccase on composite carbon paste electrodes. Multi-walled carbon nanotubes (MWCNTs) paste electrode modified by dispersion of laccase (3%, w/w) within the optimum composite matrix (60:40%, w/w, MWCNTs and paraffin binder) showed the best performance, with excellent electron transfer kinetic and catalytic effects related to the redox process of the substrate 4-aminophenol. No metal or anti-interference membrane was added. Based on the inhibition of laccase activity, pirimicarb can be determined in the range 9.90×10−7 to 1.15×10−5molL−1 using 4-aminophenol as substrate at the optimum pH of 5.0, with acceptable repeatability and reproducibility (relative standard deviations lower than 5%). The limit of detection obtained was 1.8×10−7molL−1 (0.04mgkg−1 on a fresh weight vegetable basis). The high activity and catalytic properties of the laccase-based biosensor are retained during ca. one month. The optimized electroanalytical protocol coupled to the QuEChERS methodology were applied to tomato and lettuce samples spiked at three levels; recoveries ranging from 91.0±0.1% to 101.0±0.3% were attained. No significant effects in the pirimicarb electroanalysis were observed by the presence of pro-vitamin A, vitamins B1 and C, and glucose in the vegetable extracts. The proposed biosensor-based pesticide residue methodology fulfills all requisites to be used in implementation of food safety programs.

Electrochemical sensor for selective determination of N-acetylcysteine in the presence of folic acid using a modified carbon nanotube paste electrode

In the present paper, a novel benzoylferrocene (BF) modified carbon nanotube paste electrode (BFCNPE) was prepared. The modified electrode was further used for the successful determination of N-acetylcysteine (NAC), and it showed an excellent electrocatalytic oxidation activity toward NAC with a lower overvoltage, pronounced current response, and good sensitivity. Under the optimized experimental conditions, the proposed electrochemical NAC sensor exhibited a linear calibration plot that ranged from 3.0×10−7 to 7.0×10−4M with a detection limit of 9.0×10−8M. Also, Square wave voltammetry (SWV) was used for simultaneous determination of NAC and folic acid (FA) at the modified electrode. Finally, the proposed method was applied to the determination of NAC in NAC tablets.

DNA-functionalized electrochemical biosensor for detection of vitamin B1 using electrochemically treated multiwalled carbon nanotube paste electrode by voltammetric methods

A simple methodology was used to develop a novel electrochemical biosensor for the determination of vitamin B1. The interaction of vitamin B1 with DNA based on the decreasing of the oxidation signal of guanine and adenine bases was studied electrochemically with a pretreated multiwalled carbon nanotube paste electrode (PMWCNTPE) using differential pulse voltammetry. The decrease in the intensity of the guanine and adenine oxidation signals after interaction with vitamin B1 was used as an indicator signals for the sensitive determination of vitamin B1. Under the optimum conditions, a linear dependence of the guanine and adenine oxidation signals was observed for the vitamin B1 concentration in the range of 1.0–80 μg mL −1 with a detection limit of 0.44 μg mL −1 at ds-DNA modified PMWCNTPE. The reproducibility and applicability of the analysis to serum, plasma and urine sample were also investigated. Vitamin B1 was also determined on a pretreated multiwalled carbon nanotube paste electrode by means of adsorptive stripping differential pulse voltammetry. The peak current was linearly dependent on Vitamin B1 concentration over the range of 0.0025–0.80 μg mL −1 , with a detection limit of 1.1 ng mL −1 Vitamin B1. Both ds-DNA-modified MWCNPTE and PMWCNTPE were applied to analyze Vitamin B1 in real samples.

생체 세포내 미량 구리의 전기화학적 검출에 관한 연구

In order to measure the minute amount of Cu(II) in our environment, cyclic voltammetry (CV) and square-wave stripping voltammetry (SWSV) were performed for a trace copper assay using bismuth immobilized on a carbon nanotube paste electrode. An analytical working range of 30 to <TEX>$240{\mu}g/L$</TEX> Cu(II) was obtained for CV and SWSV. The SWSV precision obtained was 0.47 % (n = 15) RSD in <TEX>$30.0{\mu}g/L$</TEX> Cu(II). The detection limit obtained was 3.1 ng/L Cu(II) using SWSV, while the CV yielded the nano-range detection limit through the pre-concentration step. By using this research method, Cu(II) value could be determined in the urine of human sample and in the brain of fish sample. This research can be effectively applied to other cases of measuring minute amount of Cu(II) in living organisms.

Rapid and direct determination of fructose in food: A new osmium-polymer mediated biosensor

This paper describes the development and performance of a new rapid amperometric biosensor for fructose monitoring in food analysis. The biosensor is based on the activity of fructose dehydrogenase (FDH) immobilised into a carbon nanotube paste electrode according to two different procedures. The direct wiring of the FDH in a highly original osmium-polymer hydrogel was found to offer a better enzyme entrapment compared to the immobilisation of the enzyme in an albumin hydrogel. The optimised biosensor required only 5U of FDH and kept the 80% of its initial sensitivity after 4months. During this time, the biosensor showed a detection limit for fructose of 1μM, a large linear range between 0.1 and 5mM, a high sensitivity (1.95μAcm−2mM), good reproducibility (RSD=2.1%) and a fast response time (4s).Finally, the biosensor was applied for specific determination of fructose in honey, fruit juices, soft and energy drinks. The results indicated a very good agreement with those obtained with a commercial reference kit. No significant interference was observed with the proposed biosensor.