Differential pulse voltammetric simultaneous determination of ascorbic acid,dopamine and uric acid on a glassy carbon electrode modified with electroreduced graphene oxide and imidazolium groups

A glassy carbon electrode (GCE) was anodically oxidized by cyclic voltammetry (CV) in 0.05 M sulfuric acid to introduce hydroxy groups on its surface (GCE_ox). Next, an imidazolium alkoxysilane (ImAS) is covalently tethered to the surface of the GCE_ox via silane chemistry. This electrode is further modified with graphene oxide (GO) which, dispersed in water, spontaneously assembles on the electrode surface through electrostatic interaction and π-interaction to give an electrode of type GO/ImAS/GCE. Electroreduction of GO and GCE_ox by CV yields electroreduced GO (erGO) and an electrode of the type erGO/ImAS/GCE. This electrode displays excellent electrocatalytic activity for the oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA). Three fully resolved anodic peaks (at ?50 mV, 150 mV and 280 mV vs. Ag/AgCl) are observed during differential pulse voltammetry (DPV). Under optimized conditions, the linear detection ranges are from 30 to 2000 μM for AA, from 20 to 490 μM for UA, and from 0.1 to 5 μM and from 5 μM to 200 μM (two linear ranges) for DA. The respective limits of detection (for an S/N of 3) are 10 μM, 5 μM and 0.03 μM. The GCE modified with erGO and ImAS performs better than a bare GCE or a GCE modified with ImAS only, and also outperforms many other reported electrodes for the three analytes. The method was successfully applied to simultaneous analysis of AA, DA and UA in spiked human urine.

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Graphical abstract Differential pulse voltammetric simultaneous determination of ascorbic acid, dopamine and uric acid is achieved on a glassy carbon electrode modified with electroreduced graphene oxide and imidazolium groups, through anodic treatment of glassy carbon and silane chemistry.

     

Determination of Ascorbic Acid in the Presence of Uric Acid and Folic Acid by a Nanostructured Electrochemical Sensor Based on a TiO2 Nanoparticle Carbon Paste Electrode

A carbon paste electrode (CPE), modified with novel hydroquinone/TiO₂ nanoparticles, was designed and used for simultaneous determination of ascorbic acid (AA), uric acid (UA) and folic acid (FA). The magnitude of the peak current for modified TiO₂-nanoparticle CPE (MTNCPE) increased sharply in the presence of ascorbic acid and was proportional to its concentration. A dynamic range of 1.0–1400.0 μM, with the detection limit of 6.4 × 10^?7 M for AA, was obtained using the DPV technique (pH = 7.0). The prepared electrode was successfully applied for the determination of AA, UA, and FA in real samples.     

Pt-polyaniline nanocomposite on boron-doped diamond electrode for amperometic biosensor with low detection limit

Boron-doped diamond electrodes covered with a nanostructured Pt nanoparticle-polyaniline composite have been fabricated and employed as sensitive amperometric sensors with low detection limit. A highly conductive boron-doped diamond thin film (BDD) was prepared by chemical vapor deposition, and its morphology was characterized by scanning electron microscopy and transmission electron microscopy. The nanostructured composite layer was grown on the BDD electrode by electrochemical deposition of polyaniline and Pt nanoparticles. Glucose oxidase (GOx) was then adsorptively immobilized on the modified BDD electrode. The biosensor displays a large surface area, high catalytic activity of the Pt nanoparticles, efficient electron mediation through the conducting polymer, and low background current of the electrode. The biosensor exhibits an excellent response to glucose, with a broad linear range from 5.9 μM to 0.51 mM, a sensitivity of 5.5 μA·mM^?1, a correlation coefficient (R) of 0.9947, and a detection limit of 0.10 μM. The apparent Michaelis-Menten constant (K _M ^app ) and the maximum current density of the electrode are 4.1 mM and 0.021 mA, respectively. This suggests that the immobilized GOx possesses a higher affinity for glucose at the lower K _M ^app , and that the enzymatic reaction rate constitutes the rate-limiting step of the response.     

Simultaneous voltammetric determination of 2-nitrophenol and 4-nitrophenol based on an acetylene black paste electrode modified with a graphene-chitosan composite

We describe a simple and sensitive voltammetric method for the simultaneous determination of 2-nitrophenol and 4-nitrophenol. It is based on the use of an acetylene black paste electrode modified with a graphene-chitosan composite film (denoted as Gr-Chit/ABPE). The reduction peak currents of 2-nitrophenol (at ?252 mV) and of 4-nitrophenol (at ?340 mV) in pH 1.0 solution increase significantly at the Gr-Chit/ABPE in comparison to a bare ABPE. Factors affecting sensitivity were optimized and a linear relationship is found between peak current and the concentrations of 2-nitrophenol (in the 0.4 μM to 80 μM range) and for 4-nitrophenol (in the 0.1 μM to 80 μM range). The detection limits (at an SNR of 3 and after a 30-s accumulation time) are 200 nM for 2-nitrophenol and 80 nM for 4-nitrophenol, respectively. The modified electrode was successfully applied to the direct and parallel determination of 2-nitrophenol and 4-nitrophenol in spiked water samples.

A sensitive amperometric hydrogen peroxide sensor based on thionin/EDTA/carbon nanotubes—chitosan composite film modified electrode

A sensitive amperometric sensor has been constructed for the determination of hydrogen peroxide (HP). It is based on a glassy carbon electrode modified with a composite made from thionin, EDTA, multiwalled carbon nanotubes, and chitosan. Thionin was covalently immobilized on the surface of the electrode. The sensor exhibits a powerful electrocatalytic activity for the reduction of HP. The amperometric signal is proportional to the concentration of HP in the range from 0.2 μM to 85.0 μM, with a detection limit of 0.065 μM. The sensor displays excellent selectivity, good reproducibility and long-term stability.     

Electrochemical synthesis of polyaniline in surface-attached poly(acrylic acid) network, and its application to the electrocatalytic oxidation of ascorbic acid

Acrylic acid was first electropolymerized on the surface of a gold electrode. Then, polyaniline (PANI) was electrodeposited on the poly(acrylic acid) (PAA) network to give a PANI–PAA composite film. Scanning electron microscopy and electrochemical studies confirmed the formation of PANI–PAA composite which exhibited excellent electroactivity over a wide pH range. The electro-oxidation of ascorbic acid (AA) was studied in detail. The modified electrode exhibits significantly reduced oxidation overpotential. The response towards AA is linear in the range 1.0 μM to 9.3 mM (R?=?0.9997, n?=?33) at a potential of 0.1 V (vs. SCE). The sensitivity is 207 μA mM^-1 cm^-2, and the detection limit is 1.0 μM (S/N?=?3). Interferences by uric acid and dopamine are negligible. The electrode thus enables sensitive and selective determination of AA, with a performance superior to many other PANI–based ascorbate sensors.     

Ytterbium fluoride nanoparticles on carbon nanotubes: preparation, characterization and application for simultaneous electrochemical determination of ascorbic acid, dopamine and uric acid

A novel modified glassy carbon electrode with ytterbium fluoride nanoparticles (YFNPs)-multiwalled carbon nanotubes (MWCNTs) was fabricated and then successfully used for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). YFNPs were successfully coated on the MWCNTs via the intermediate of noncovalent hydrophobic interactions of the MWCNTs surface with sodium dodecyl sulfate. The YFNPs and immobilization of YFNPs on MWCNTs were confirmed by transmission electron microscopy. The particle size of YFNPs was measured to be around 45 nm. The catalytic peak currents for AA, DA and UA were linearly dependent on their concentrations in the range of 2.0–600.0, 2.0–560.0 and 1.8–640.0 μM, respectively, with the corresponding detection limits of 0.77, 0.22 and 0.17 μM. The modified electrode provided good sensitivity and stability, and was successfully applied for the simultaneous determination of AA, DA and UA in human blood serum and urine samples.     

Poly(m-ferrocenylaniline) modified carbon nanotubes-paste electrode encapsulated in nafion film for selective and sensitive determination of dopamine and uric acid in the presence of ascorbic acid

A nafion covered carbon nanotubes-paste electrode modified with poly(m-ferrocenylaniline), (Nf/p(FcAni)-CNTsPE), provides a novel voltammetric sensor for the selective determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA). We studied the electrochemical activity of Nf/p(FcAni)-CNTsPE toward DA, UA, and AA by differential pulse voltammetry (DPV). DA and UA anodic peaks appear at 0.30 and 0.45 V, respectively while an anodic peak for AA was not observed. DPV oxidation peak values are linearly dependent on DA concentration over the range 1–150 μM (r² = 0.992), and on UA concentration over the range 5–250 μM (r² = 0.997). DA and UA detection limits are estimated to be 0.21 and 0.58 μM, respectively. The modified electrode shows both good selectivity and reproducibility for the selective determination of DA and UA in real samples. Finally, the modified electrode was successfully applied for the determination of DA and UA in pharmaceutical or biological sample fluids.     

Electrochemical determination of nitrite via covalent immobilization of a single-walled carbon nanotubes and single stranded deoxyribonucleic acid nanocomposite on a glassy carbon electrode

A novel method has been developed for determination of nitrite by modifying the surface of a glassy carbon electrode (GCE) using single-walled carbon nanotubes with covalently immobilized single-strand deoxyribonucleic acid. The modified electrodes were characterized by field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. The results demonstrate that the nanotube-DNA nanocomposite has been successfully immobilized on the surface of the GCE. The new electrode, under optimum conditions at room temperature, exhibits excellent electrocatalytic activity towards the oxidation of nitrite, with a significantly reduction of the overpotential. The linear range for the detection of nitrite is from 0.6 to 540 μM, with a sensitivity of 0.216 μA?μM^?1, and a detection limit as low as 0.15 μM. The electrode showed good reproducibility and high stability and was successfully used to analyze nitrite in water and sausage samples.     

The Influence of Gold Nanoparticles on Simultaneous Determination of Uric Acid and Ascorbic Acid

A three-dimensional L-cysteine (L-cys) monolayer assembled on gold nanoparticles (GNP) providing simultaneous detection of uric acid (UA) and ascorbic acid (AA) was studied in this work. The cyclic voltammetry demonstrated that, at a bare glassy carbon electrode (GCE) or planar gold electrode, the mixture of UA and AA showed one overlapped oxidation peak; whereas when the electrode was modified with GNP, the oxidation peaks for UA and AA were separated. While a GNP modified electrode was further modified with L-cys monolayer (L-cys/GNP/GCE), namely, three-dimensional L-cys monolayer, a better separation for UA and AA response was obtained. Interestingly, the L-cys monolayer-modified planar gold electrode presented a block effect on the oxidation of AA, which was facilitated by the three-dimensional L-cys monolayer attributed to its distinct structure. The pH of solution presented a noticeable effect on the separation of UA and AA at GNP modified electrodes with or without L-cys monolayer. Wide concentration ranges from 2 × 10^?6?1 × 10^?3 M to UA and 2 × 10^?6?8 × 10^?4 M to AA could be obtained at L-cys/GNP/GCE.     

A glassy carbon electrode modified with the nickel(II)-bis(1,10-phenanthroline) complex and multi-walled carbon nanotubes, and its use as a sensor for ascorbic acid

A glassy carbon electrode (GCE) was modified with the nickel(II)-bis(1,10-phenanthroline) complex and with multi-walled carbon nanotubes (MWCNTs). The nickel complex was electrodeposited on the MWCNTs by cyclic voltammetry. The modified GCE displays excellent electrocatalytic activity to the oxidation of ascorbic acid (AA). The effects of fraction of MWCNTs, film thickness and pH values were optimized. Response to AA is linear in the 10 to 630 μM concentration range, and the detection limit is 4 μM (at a signal-to-noise ratio of 3:1). The modified electrode was applied to determine AA in vitamin C tablets and in spiked fruit juice.

Amperometric sensor based on carbon nanotubes and electropolymerized vanillic acid for simultaneous determination of ascorbic acid,dopamine, and uric acid

This paper describes the development of a simple and efficient nanostructured platform based on multi-walled carbon nanotubes (MWCNT) functionalized with an in situ generated vanillic acid (VA) polymer. It was used as an analytical sensor for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electropolymerization process of VA, performed on MWCNT-modified glassy carbon electrode, produces three redox systems based on quinone/hydroquinone functionality, as observed by cyclic voltammetry. The amperometric sensor has as figures of merit for the simultaneous determination of AA, DA, and UA the following values: for AA, a linear range of 5–120 μM and detection limit of 3.5 μM; for DA, a linear range of 5–120 μM and detection limit of 4.5 μM; and for UA, a linear range of 5–120 μM and a detection limit of 1.5 μM. From the obtained performance, the development of the platform based on MWCNT/poly-VA is justified for the simultaneous determination of AA, DA, and UA.     

Non-enzymatic hydrogen peroxide sensor using an electrode modified with iron pentacyanonitrosylferrate nanoparticles

An electrochemical sensor was developed for determination of hydrogen peroxide (HP) based on a carbon ceramic electrode modified with iron pentacyanonitrosylferrate (FePCNF). The surface of an iron-doped CCE was derivatized in a solution of PCNF by cycling the electrode potential between ?0.2 and +1.3 V for about 60 times. The morphology and the composition of the resulting electrode were characterized by scanning electron microscopy and Fourier transform infrared techniques. The electrode displayed excellent response to the electro-oxidation of HP which is linearly related to its concentration in the range from 0.5 μM to 1300 μM. The detection limit is 0.4 μM, and the sensitivity is 849 A M ^?1?cm ^?2. The modified electrode was used to determination of HP in hair coloring creams as real samples.     

Simultaneous determination of dopamine and uric acid in the presence of ascorbic acid using a gold electrode modified with carboxylated graphene and silver nanocube functionalized polydopamine nanospheres

A voltammetric sensor is presented for the simultaneous determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA). It is based on a gold electrode (GE) modified with carboxyl-functionalized graphene (CFG) and silver nanocube functionalized DA nanospheres (AgNC@PDA-NS). The AgNC@PDA-NS nanocomposite was characterized by scanning electron microscopy and UV-Vis spectroscopy. The electrochemical behavior of the modified electrode was evaluated by electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. The modified electrode displays good electrocatalytic activity towards DA (typically at 0.14 V vs. Ag/AgCl) and UA (typically at 0.29 V vs. Ag/AgCl) even in the presence of ascorbic acid. Response to DA is linear in the concentration range of 2.5 to 130 μM with a detection limit of 0.25 μM. Response to UA is linear in the concentration range of 10 to 130 μM with a detection limit of 1.9 μM. In addition, the sensitivity for DA and UA is 0.538 and 0.156 μA μM^?1 cm^?2, respectively. The modified electrode also displays good stability, selectivity and reproducibility.

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Graphical abstract The gold electrode modified with polydopamine nanospheres functionalized with silver nanocube and carboxylated graphene is used for simultaneous determination of DA and UA in the presence of AA, with wide linear range and low detection limit.

     

A thin poly(acridine orange) film containing reduced graphene oxide for voltammetric simultaneous sensing of ascorbic acid and uric acid

We have fabricated, in a single step, carbon ceramic electrodes modified with a poly(acridine orange) film containing reduced graphene oxide. They display electrocatalytic activity to ascorbic acid (AA) and uric acid (UA) at pH 4.5. The anodic peak potentials of AA and UA are separated by 276 mV so that they can be well resolved in cyclic voltammetry. UA and AA were simultaneously determined in a mixture at working potentials of 170 and 400 mV, respectively. Under optimized conditions, the calibration curves for AA and UA cover the 0.8–5,000 μM and 0.6–900 μM concentration range, respectively, while detection limits are 0.3 μM and 0.2 μM. The electrode was applied to determine AA and UA in urine samples.

Immobilization of monoamine oxidase on eggshell membrane and its application in designing an amperometric biosensor for dopamine

An amperometric biosensor for dopamine is described. It is based on the enzyme monoamine oxidase immobilized on a glutaraldehyde-activated eggshell membrane that was deposited on a glassy carbon electrode. The Michaelis-Menten constant (Km) is 0.087 mM. Optimum pH and temperature conditions were obtained at pH 7.0 and 37 °C, respectively. The sensor showed a detection limit of 20 μM, a linear range from 50 μM to 250 μM, and a storage stability of ~25 days. In order to further improve the performance, a Nafion coating was applied on the electrode surface which gave favorable results with respect to shelf life of the enzyme (~40 days), the limit of detection, and the selectivity over ascorbic acid and uric acid.     

Amperometric Biosensors Based on Platinum Nanowires

Abstract

Platinum nanowires (PtNW) were prepared by an electrodeposition strategy using nanopore alumina template. The nanowires prepared were dispersed in chitosan (CHIT) solution and stably immobilized onto the surface of glassy carbon electrode (GCE). The electrochemical behavior of PtNW‐modified electrode and its application to the electrocatalytic reduction of hydrogen peroxide (H₂O₂) are investigated. The modified electrode allows low potential detection of hydrogen peroxide with high sensitivity and fast response time. As an application example, the glucose oxidase was immobilized onto the surface of PtNW‐modified electrode through cross‐linking by glutaric dialdehyde. The detection of glucose was performed in phosphate buffer at –0.2 V. The resulting glucose biosensor exhibited a short response time (<8 s), with a linear range of 10^?5?10^?2 M and detection limit of 5×10^?6 M.     

Platinum nanoparticles–decorated graphene-modified glassy carbon electrode toward the electrochemical determination of ascorbic acid,dopamine, and paracetamol

In the present study, we report the synthesis and characterization of platinum nanoparticles decorated graphene (GPtNPs) nanocomposite toward the electrochemical determination of ascorbic acid (AA), dopamine (DA), and paracetamol (PCT). GPtNPs demonstrated synergistic catalytic activity with enhanced currents in all of the measurements when compared with graphene-modified glassy carbon electrode (G-GCE) and bare GCE. The nanocomposite exhibited low overpotential for AA oxidation and good peak-to-peak separation of 218.0, 218.0, and 436.0 mV for AA–DA, DA–PCT, and AA–PCT, respectively. Cyclic voltammetry (CV) and chronoamperometry (CA) determination of AA, DA, and PCT showed wide linearity ranges. CV determination of AA exhibited linearity range from 300 μM to 20.89 mM and from 22.02 to 39.87 mM. DA determination using CV exhibited linearity range from 5 to 104 μM and from 114 to 684 μM, whereas CA determination of PCT showed a linearity range from 20 μM to 6.43 mM. Differential pulse voltammetry determinations of AA, DA, and PCT exhibited low detection limits of 300, 5, and 5 μM, respectively.     

A glassy carbon electrode modified with a polyaniline doped with silicotungstic acid and carbon nanotubes for the sensitive amperometric determination of ascorbic acid

We report on an electrochemical sensor for the sensitive amperometric determination of ascorbic acid (AA). Aniline containing suspended silicotungstic acid and carbon nanotubes was electropolymerized on the surface of a glassy carbon electrode in a single step which provides a simple and controllable method and greatly improves the electrocatalytic oxidation of AA. The effects of scan rate, solution pH and working potential were studied. A linear relationship exists between the current measured and the concentration of AA in the range from 1 μM to 10 μM and 0.01 mM to 9 mM, with a limit of detection as low as 0.51 μM (S/N?=?3). The sensor is selective, stable and satisfyingly reliable in real sample experiments. In our eyes, it has a large potential for practical applications.