Ionic Liquid Modified Carbon Paste Research Articles

Direct electrochemistry and electrocatalysis of myoglobin using an ionic liquid-modified carbon paste electrode coated with Co3O4 nanorods and gold nanoparticles

A nanohybrid biomaterial was fabricated by mixing Co3O4 nanorods, gold nanoparticles (Au-NPs) and myoglobin (Mb), and depositing it on the surface of a carbon paste electrode containing the ionic liquid N-hexylpyridinium hexafluorophosphate as the binder. UV–vis and FT-IR revealed the Mb in the composite film to have remained in its native structure. A pair of well-defined redox peaks appears in cyclic voltammograms and indicates direct electron transfer from the Mb to the underlying electrode. The results are attributed to the favorable orientation of Mb in the composite film, to the synergistic effects of Co3O4 nanorods and Au-NPs. The modified electrode shows excellent electrocatalytic ability towards the reduction of substrates such as trichloroacetic acid and nitrite, and displays good stability and reproducibility.

A novel biosensor based on ZnO nanoparticle/1,3-dipropylimidazolium bromide ionic liquid-modified carbon paste electrode for square-wave voltammetric determination of epinephrine

The direct electrochemistry of epinephrine (EP) on a modified carbon paste electrode (CPE) was described. The electrode was modified with Zinc oxide (ZnO) nanoparticles and 1,3-dipropylimidazolium bromide as a binder. The oxidation peak potential of EP at the surface of the ionic liquid ZnO nanoparticle CPE (IL/ZnO/NP/CPE) appeared at 350 mV, which was about 80 mV lower than the oxidation peak potential at the surface of the traditional carbon CPE under a similar condition. On other hand, the oxidation peak current was increased for about three times at the surface of IL/ZnO/NP/CPE compared to CPE. The linear response range and detection limit were found to be 0.09–800 μmol L−1 and 0.06 μmol L−1, respectively. Other physiological species did not interfere in the determination of EP at the surface of the proposed sensor in the optimum condition. The proposed sensor was successfully applied for the determination of EP in real samples.

High sensitive voltammetric sensor based on Pt/CNTs nanocomposite modified ionic liquid carbon paste electrode for determination of Sudan I in food samples

In this work, a simple and high sensitivity electrochemical sensor was developed to determine Sudan I based on Pt/CNTs nanocomposite ionic liquid modified carbon paste electrode (Pt/CNTs/ILCPE) using cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV) methods. The novel sensor exhibited an obviously catalytic activity towards the oxidation of Sudan I, which can be confirmed by the increased oxidation peak current and the decreased oxidation peak potential when compared with the bare carbon paste electrode (CPE). The electron transfer coefficient (α), diffusion coefficient (D), and charge transfer resistance (Rct) of Sudan I at the modified electrode were calculated. The linear response range and detection limit were found to be 0.008–600μmolL−1 and 0.003μmolL−1, respectively. Other species did not interfere with the determination of Sudan I at a surface of propose sensor in the optimum condition. The proposed sensor was successfully applied for the determination of Sudan I in food samples with satisfactory results.

Application of ZnO/CNTs Nanocomposite Ionic Liquid Paste Electrode as a Sensitive Voltammetric Sensor for Determination of Ascorbic Acid in Food Samples

In this study, a simple and rapid analytical method development for ascorbic acid (AA) determination in food samples by using differential pulse voltammetry (DPV) method on ZnO/CNTs nanocomposite ionic liquid modified carbon paste electrode. For this, several parameters, such as ZnO/CNTs nanocomposite, ionic liquid ratio, and pH, have been studied. The cyclic voltammogram showed an irreversible oxidation peak at 0.61 V (vs. Ag/AgClsat), which corresponded to the oxidation of AA. Compared to common carbon paste electrode, the electrochemical response was greatly improved. Under the optimized conditions, the oxidation peak current of AA showed linear dynamic range 0.1–450 μmol l−1 with a detection limit of 0.07 μmol l−1, using the DPV method. The proposed sensor was successfully applied to the determination of AA in fresh vegetable juice, fruit juices and food supplement samples without previous preparation and was compared with a published electrochemical method.

Electrochemical behavior of morphine at ZnO/CNT nanocomposite room temperature ionic liquid modified carbon paste electrode and its determination in real samples

In this paper we report synthesis and application of ZnO/CNT nanocomposite and 1-methyl-3-butylimidazolium bromide as high sensitive sensors for voltammetric determination of morphine using carbon paste electrode. The ZnO/CNT nanocomposite was characterized with different methods such as TEM, SEM and XRD. The electrochemical oxidation of morphine on the new ZnO/CNTs ionic liquid carbon paste electrode (ZnO/CNTs/IL/CPE) was carefully studied. The oxidation peak potential of morphine on the ZnO/CNTs/IL/CPE appeared at 520mV, which was about 75mV decrease of the overpotential compared to that obtained on the traditional carbon paste electrode (CPE) and the oxidation peak current was increased for about 5.5 times. The electrochemical parameter of morphine on the ZnO/CNTs/IL/CPE was calculated with the charge transfer coefficient (α). Based on the relationship of the oxidation peak current and the concentration of morphine a sensitive analytical method was established with cyclic voltammetry. The linear range for morphine determination was in the range from 0.1 to 700μmolL−1 and the detection limit was calculated as 0.06μmolL−1 (3σ). Finally, the proposed method was also examined as a selective, simple and precise electrochemical sensor for the determination of morphine in real samples such as urine and ampoule.

Electrochemical behavior of labetalol at an ionic liquid modified carbon paste electrode and its electrochemical determination

Electrochemical behavior of labetalol (LBT) at carbon paste electrode (CPE) and an ionic liquid1-benzyl-3-methylimidazolehexafluorophosphate([BnMIM]PF6)modified carbon paste electrode([BnMIM]PF6/CPE)in Britton-Robinson buffer solution (pH 2.0) was investigated by cyclic voltammetry (CV) and square wave voltammetric (SWV). The experimental results showed that LBT at both the bare CPE and [BnMIM]PF6/CPEshowed an irreversible oxidation process, but at [BnMIM]PF6/CPE its oxidation peak current increased greatly and the oxidation peak potential shifted negatively. The electrode reaction process is a diffusion-controlled process involving one electron transferring accompanied by a participation of one proton at [BnMIM]PF6/CPE. At the same time, the electrochemical kinetic parameters were determined. Under the optimized electrochemical experimental conditions, the oxidation peak currents were proportional to LBT concentration in the range of 7.0 x 10-6-1.0 x 10-4 mol L-1 with the limit of detection(LOD, S/N=3) of 4.810 x 10-8 mol L-1and the limit of quantification(LOQ, S/N=10) of 1.60 x 10-7 mol L-1, respectively. The proposed method was successfully applied in the determination of LBT content in commercial tablet samples.

Electrochemical Behaviours and Detection of Adenosine‐5¢‐triphosphate on an Ionic Liquid Modified Carbon Paste Electrode

AbstractIn this paper a new electrochemical method based on the ionic liquid modified carbon paste electrode (IL‐CPE) was proposed for the determination of adenosine‐5′‐triphosphate (ATP) in a pH 4.5 Britton‐Robinson (B‐R) buffer solution. IL‐CPE was prepared by using 1‐butyl‐3‐methylimidazolium trifluoroacetate (BMIMCF3COO) as the modifier. Cyclic voltammetry was used to investigate the electrochemical behaviors of ATP on the IL‐CPE, and the results indicated that IL‐CPE exhibited strong electrocatalytic ability to promote the oxidation of ATP with a single well‐defined irreversible adsorption‐controlled oxidation peak appeared. The electrochemical reaction parameters of ATP were calculated with the results of the electron transfer coefficient (α) as 0.40, the electron transfer number (n) as 1.17, the apparent heterogeneous electron transfer rate constant (ks) as 3.66 × 10‐6 s‐1 and the surface coverage (Γτ) as 2.48 × 10‐9 mol cm‐2. Under the selected conditions the proposed IL‐CPE showed good performances to the ATP detection in the concentration range from 0.1 to 1000.0 μmol L‐1 with the detection limit as 3.65 × 10‐8 mol L‐1 (3σ) by differential pulse voltammetry. The method showed good selectivity to the ATP detection without the interferences of coexisting substances and was successfully applied to the ATP injection samples detection with satisfactory results.

Electrochemical behaviors and electrochemical determination of carbamazepine at ionic liquid modified carbon paste electrode in the presence of sodium dodecyl sulfate

The electrochemical behavior and electrochemical determination of carbamazepine (CBZ) at hydrophobic ionic liquid 1-Benzyl-3-Methylimidazole hexafluorophosphate ([BnMIM]PF6) modified carbon paste electrode ([BnMIM]PF6/CPE) in the presence of sodium dodecyl sulfate (SDS) were investigated. A well-defined and sensitive oxidation peak was observed at [BnMIM]PF6/CPE in the presence of SDS and 0.10 M phosphate buffer solution (pH 6.80). The oxidation peak current of CBZ increased significantly at [BnMIM]PF6/CPE in the presence of SDS compared with that in the absence of SDS at carbon paste electrode. It suggested that both SDS and [BnMIM]PF6/CPE show an obvious enhancing effect on the electrochemical oxidation of CBZ. The electrochemical kinetic parameters for CBZ at [BnMIM]PF6/CPE in aqueous SDS solutions were also determined by Chronocoulometry and Chronoamperometry. Finally, the experimental conditions were optimized, and a new electrochemical method of determination for CBZ had been established. The oxidation peak current was linearly dependent on CBZ concentration in the range of 7.0 ?M to 0.7 mM with a detection limit of 0.98 ?M (signal to noice ratio, S/N = 3). The relative standard deviation for six determinations of 0.10 mM CBZ was between 1.40 and 2.13%. The proposed method was applied in the determination of CBZ in commercial tablet samples.

Simultaneous electrochemical determination of epinephrine and uric acid at 1-butyl-4-methyl-pyridinium tetrafluroborate ionic liquid modified carbon paste electrode: A voltammetric study

An ionic liquid (IL) film 1-butyl-4-methyl-pyridinium tetrafluroborate modified carbon paste electrode (BMPTB/CPE) was fabricated and the electrochemical behavior of epinephrine at the modified electrode was investigated by cyclic voltammetric and differential pulse voltammetric techniques. A well-defined oxidation peak was observed at 0.21 V and the significant increase in peak current at modified carbon paste electrode compared to bare carbon paste electrode was obtained. The effect of scan rate on the oxidation of epinephrine was examined and it was found that the anodic peak current was proportional to the concentration of epinephrine in the range from 0.5 × 10 − 5 to 4.5 × 10 − 5 M. The BMPTB/CPE showed significantly higher sensitivity, and selectivity and used for the simultaneous determination of epinephrine and uric acid. The advantages of this biosensor showed simplicity, inherent stability and ability for simultaneous determination without using any other separation systems. The analytical performance of this biosensor has been evaluated for detection of epinephrine injection in serum as real sample.

Electrochemical deoxyribonucleic acid biosensor based on the self-assembly film with nanogold decorated on ionic liquid modified carbon paste electrode

An electrochemical DNA biosensor was fabricated by self-assembling probe single-stranded DNA (ssDNA) with a nanogold decorated on ionic liquid modified carbon paste electrode (IL-CPE). IL-CPE was fabricated using 1-butylpyridinium hexafluorophosphate as the binder and the gold nanoparticles were electrodeposited on the surface of IL-CPE (Au/IL-CPE). Then mercaptoacetic acid was self-assembled on the Au/IL-CPE to obtain a layer of modified film, and the ssDNA probe was further covalently-linked with mercaptoacetic acid by the formation of carboxylate ester with the help of N-(3-dimethylamino-propyl)-N′-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The hybridization reaction with the target ssDNA was monitored with methylene blue (MB) as the electrochemical indicator. Under the optimal conditions, differential pulse voltammetric responses of MB was proportional to the specific ssDNA arachis sequences in the concentration range from 1.0 × 10 −11 to 1.0 × 10 −6 mol L −1 with the detection limit as 1.5 × 10 −12 mol L −1 (3 σ). This electrochemical DNA sensor exhibited good stability and selectivity with the discrimination ability of the one-base and three-base mismatched ssDNA sequences. The polymerase chain reaction product of arachis Arabinose operon D gene was successfully detected by the proposed method, which indicated that the electrochemical DNA sensor designed in this paper could be further used for the detection of specific ssDNA sequence.

Electrochemical Oxidation of 2’-deoxyguanosine-5’-triphosphate on Ionic Liquid Modified Carbon Paste Microelectrode and its Sensitive Detection

Electrochemical Oxidation of 2’-deoxyguanosine-5’-triphosphate on Ionic Liquid Modified Carbon Paste Microelectrode and its Sensitive Detection

Simultaneous Determination of Copper, Lead, and Cadmium at Hexagonal Mesoporous Silica Immobilized Quercetin Modified Carbon Paste Electrode

A new method was developed for simultaneous determination of copper, lead, and cadmium, based on their voltammetric response at a carbon paste electrode modified with hexagonal mesoporous silica (HMS) immobilized quercetin (HMS-Qu/CPE). Compared with quercetin modified carbon paste electrode (Qu/CPE) and quercetin ionic liquid modified carbon paste electrode (Qu-IL/CPE), the HMS-Qu/CPE exhibited improved selectivity and high sensitivity toward the detection of copper, lead, and cadmium. The properties of the HMS-Qu/CPE in 0.1 M HCOONa-HCl buffer solution (pH4.7) were investigated by adsorptive stripping voltammetry (ASV) and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of copper, lead, and cadmium at the modified electrodes and factors affecting the preconcentration procedures were also investigated. Detection limits of 5.0, 0.8, 1.0 nM for copper, lead, and cadmium were obtained, respectively. The method is simple, fast, sensitive, and selective, and is successfully applied to soil sample.

Electropolymerization of Methylene Blue on Carbon Ionic Liquid Electrode and Its Electrocatalysis to 3,4‐Dihydroxybenzoic Acid

AbstractIn this paper an ionic liquid modified carbon paste electrode (CILE) was prepared and methylene blue (MB) was electropolymerized on the CILE by using the cyclic voltammetric technique in the potential range from −1.0 V to 0.8 V (vs. SCE). A stable polymer film was obtained and exhibited a pair of redox peaks. The morphology and characteristics of poly(methylene blue) (PMB) film was studied by the techniques such as scanning electron microscopy and electrochemical impedance spectroscopy. This PMB modified CILE (PMB/CILE) showed excellent electrocatalytic response to 3,4‐dihydroxybenzoic acid with the increase of the electrochemical responses. The oxidation peak current had a linear relationship with 3,4‐dihydroxybenzoic acid concentration in the range of 5.0 × 10−4 ∼ 3.0 × 10−2 mol L−1 and the detection limit was 1.72 × 10−4 Mol L−1 (3 σ).

Electrochemistry of hemoglobin entrapped in a Nafion/nano-ZnO film on carbon ionic liquid electrode

A stable composite film composed of the ionomer Nafion, the ZnO nanoparticle and the protein hemoglobin was cast on the surface of an ionic liquid modified carbon paste electrode (CILE) to establish a modified electrode denoted as Nafion/nano-ZnO/Hb/CILE. UV–vis and FT-IR spectrum showed that hemoglobin in the film retained its native conformation. The electrochemical behaviors of hemoglobin entrapped in the film were carefully investigated with cyclic voltammetry. A pair of well-defined and quasi-reversible redox voltammetric peaks for Hb Fe(III)/Fe(II) was obtained with the standard potential ( E 0′) located at − 0.344 V ( vs. SCE) in phosphate buffer solution (PBS, pH 7.0), which was attributed to the direct electron transfer of Hb with electrode in the microenvironments of ZnO nanoparticle and ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF 6). The electrochemical parameters of Hb in the composite film were further carefully calculated with the results of the electron-transfer rate constant ( k s ) as 0.139 s − 1 , the charge transfer coefficient ( α) as 0.413 and the number of electron transferred ( n) as 0.95. The Hb modified electrode showed good electrocatalytic ability toward the reduction of trichloroacetic acid (TCA).

Electrochemical behaviors of metol on hydrophilic ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate-modified electrode

In this paper a hydrophilic ionic liquid of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF 4) was used as modifier to make a new kind of ionic liquid-modified carbon paste electrode (IL-CPE), which was further characterized by different methods including electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and scanning electron microscope (SEM). The fabricated IL-CPE showed good electrocatalytic behaviors towards the oxidation of metol with the enhancement of the redox peak current and the decrease of the peak-to-peak separation. The electrochemical behaviors of metol on the IL-CPE were carefully studied and the electrochemical parameters were calculated. Based on the electrocatalytic reaction, a new electrochemical method for the metol determination was established in the concentration range from 4.0 × 10 −6 to 5.0 × 10 −3 mol L −1 by cyclic voltammetry with the detection limit estimated to be 2.0 × 10 −6 mol L −1 (3 σ). The established method was successfully applied to the synthetic samples and photographic solutions detection with good recovery.

Electrochemical behavior and determination of rutin on a pyridinium-based ionic liquid modified carbon paste electrode

In this paper the electrochemical behavior of rutin on a pyridinium-typed ionic liquid modified carbon paste electrode (IL-CPE) was investigated and further used for rutin sample determination. The IL-CPE showed strong electrocatalytic effects to the oxidation of rutin. In phosphate buffer solution (PBS, pH 2.5; 0.1 M) a pair of well-defined cyclic voltammetric redox peaks of rutin appeared with the redox peak located at 512 mV (Epa) and 448 mV (Epc) ( vs. SCE), respectively. The redox peak current was increased about 27.5 times more than that on traditional carbon paste electrode (CPE). The electrochemical parameters of rutin on the IL-CPE were calculated with the results of the charge transfer coefficient ( α), the number of electron transfer ( n) and the electrode reaction rate constant ( k s ) as 0.53, 1.80 and 2.39 s −1, respectively. The cathodic peak currents increased linearly with the concentration of rutin in the range from 5.0 × 10 −7 to 1.0 × 10 −4 M with the detection limit as 3.58 × 10 −7 M (3 σ). The relative standard deviation (RSD) of 10 successive detection of 5.0 × 10 −5 M rutin was 4.2%. The method was successfully applied to the determination of rutin content in tablets samples with good recovery. The modified electrode showed good stability and reproducibility without the influence of the coexisting substances.

Sensitive voltammetric determination of rutin at an ionic liquid modified carbon paste electrode

An ionic liquid modified carbon paste electrode (IL/CPE) had been fabricated by using hydrophilic ionic liquid 1-amyl-3-methylimidazolium bromide ([AMIM]Br) as a modifier. The IL/CPE was characterized by scanning electron microscope and voltammetry. Electrochemical behavior of rutin at the IL/CPE had been investigated in pH 3.29 Britton–Robinson (B–R) buffer solution by cyclic voltammetry (CV) and square wave voltammetry (SWV). The experimental results suggested that the modified electrode exhibited an electrocatalytic activity toward the redox of rutin. The electron transfer coefficient ( α) and the standard rate constant ( k s) of rutin at the modified electrode were calculated. Under the selected conditions, the reduction peak current was linearly dependent on the concentration of rutin in the range of 4.0 × 10 −8 to 1.0 × 10 −5 mol L −1 ( r = 0.9998), with a detection limit of 1.0 × 10 −8 mol L −1 (S/N = 3). The relative standard deviation (R.S.D.) for six times successful determination of 8.0 × 10 −7 mol L −1 rutin was 1.2%. The proposed method was applied to determine rutin in tablet and urine sample. In addition, the IL/CPE exhibited a distinct advantage of simple preparation, surface renewal, good reproducibility and good stability.

Fabrication and Electrochemical Behavior of Hemoglobin Modified Carbon Ionic Liquid Electrode

AbstractA new hemoglobin (Hb) and room temperature ionic liquid modified carbon paste electrode was constructed by mixing Hb with 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF6) and graphite powder together. The Hb modified carbon ionic liquid electrode (Hb‐CILE) was further characterized by FT‐IR spectra, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Hb in the carbon ionic liquid electrode remained its natural structure and showed good direct electrochemical behaviors. A pair of well‐defined quasireversible redox peaks appeared with the apparent standard potential (E′) as −0.334 (vs. SCE) in pH 7.0 phosphate buffer solution (PBS). The electrochemical parameters such as the electron transfer number (n), the electron transfer coefficient (α) and the heterogeneous electron transfer kinetic constant (ks) of the electrode reaction were calculated with the results as 1.2, 0.465 and 0.434 s−1, respectively. The fabricated Hb‐CILE exhibited excellent electrocatalytic activity to the reduction of H2O2. The calibration range for H2O2 quantitation was between 8.0×10−6 mol/L and 2.8×10−4 mol/L with the linear regression equation as Iss (μA)=0.12 C (μmol/L)+0.73 (n=18, γ=0.997) and the detection limit as 1.0×10−6 mol/L (3σ). The apparent Michaelis–Menten constant (KMapp) of Hb in the modified electrode was estimated to be 1.103 mmol/L. The surface of this electrochemical sensor can be renewed by a simple polishing step and showed good reproducibility.

Direct electrochemistry of single-stranded DNA on an ionic liquid modified carbon paste electrode

Electrochemical oxidation of thermally denatured single-stranded DNA (ssDNA) was studied on a room temperature ionic liquid N-butylpyridinium hexafluorophosphate (BPPF 6) modified carbon paste electrode (IL-CPE). A distinct oxidation peak appeared at +0.772 V (vs. SCE) on the IL-CPE after preconcentration of ssDNA at +0.35 V for 160 s in pH 7.0 phosphate buffer solution (PBS), which was attributed to the oxidation of guanine residue on the ssDNA molecular structure. The results showed an apparent negative shift of the oxidation peak potential and a great enhancement of the oxidation peak current on the IL-CPE compared with that of CPE. The electrochemical parameters of ssDNA on the IL-CPE were further calculated. Under the selected conditions, a linear calibration curve for ssDNA detection was obtained in the concentration range from 10.0 to 110.0 μg mL −1 with the detection limit of 1.5 μg mL −1(3σ).

Electrocatalytic oxidation of dopamine at an ionic liquid modified carbon paste electrode and its analytical application

A room-temperature ionic liquid N-butylpyridinium hexafluorophosphate was used as a binder to construct an ionic liquid modified carbon paste electrode, which was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The ionic liquid carbon paste electrode (IL-CPE) showed enhanced electrochemical response and strong analytical activity towards the electrochemical oxidation of dopamine (DA). A pair of well-defined quasireversible redox peaks of DA appeared, with the redox peaks located at 215 mV (E (pa)) and 151 mV (E (pc)) (vs. the saturated calomel electrode, SCE) in pH 6.0 phosphate buffer solution. The formal potential (E (0')) was calculated as 183 mV (vs. SCE) and the peak-to-peak separation as 64 mV. The electrochemical behavior of DA on the IL-CPE was carefully investigated. Under the optimal conditions, the anodic peak currents increased linearly with the concentration of DA in the range 1.0 x 10(-6)-8.0 x 10(-4) mol/L and the detection limit was calculated as 7.0 x 10(-7) mol/L (3sigma). The interferences of foreign substances were investigated and the proposed method was successfully applied to the determination of DA injection samples. The IL-CPE fabricated was sensitive, selective and showed good ability to distinguish the coexisting ascorbic acid and uric acid.