Showing papers on "Amperometry published in 2013"

Highly sensitive and selective nonenzymatic detection of glucose using three-dimensional porous nickel nanostructures.

Abstract: Highly sensitive and selective nonenzymatic detection of glucose has been achieved using a novel disposable electrochemical sensor based on three-dimensional (3D) porous nickel nanostructures. The enzyme-free sensor was fabricated through in situ growing porous nickel networks on a homemade screen-printed carbon electrode substrate via electrochemically reducing the Ni2+ precursor, along with continuously liberating hydrogen bubbles. The resulting nickel-modified electrode was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), powder X-ray diffractometry (XRD), and electrochemical techniques. Cyclic voltammetric, alternating-current impedance, and amperometric methods were used to investigate the catalytic properties of the assembled sensor for glucose electro-oxidation in alkaline media. Under optimized conditions, the enzymeless sensor exhibited excellent performance for glucose analysis selectively, offering a much wi...

Ultrasensitive Detection of Dopamine Using a Carbon Nanotube Network Microfluidic Flow Electrode

Abstract: The electrochemical measurement of dopamine (DA), in phosphate buffer solution (pH 7.4), with a limit of detection (LOD) of ∼5 pM in 50 μL (∼ 250 attomol) is achieved using a band electrode comprised of a sparse network of pristine single-walled carbon nanotubes (SWNTs), which covers <1% of the insulating substrate. The SWNT electrodes are deployed as amperometric (anodic) detectors in microfluidic cells, produced by microstereolithography, designed specifically for flow injection analysis (FIA). The flow cells, have a channel (duct) geometry, with cell height of 25 μm, and are shown to be hydrodynamically well-defined, with laminar Poiseuille flow. In the arrangement where solution continuously flows over the electrode but the electrode is only exposed to the analyte for short periods of time, the SWNT electrodes do not foul and can be used repeatedly for many months. The LOD for dopamine (DA), reported herein, is significantly lower than previous reports using FIA–electrochemical detection. Furthermore,...

Multi-walled carbon nanotube modified carbon paste electrode as a sensor for the amperometric detection of L-tryptophan in biological samples.

Abstract: An electrochemical sensor for the amperometric determination of l -tryptophan (Trp) was fabricated by modifying the carbon paste electrode (CPE) with multi-walled carbon nanotubes (MWCNTs) using drop cast method. 4.0 μL of the dispersion containing 2.0 mg of MWCNTs in 1.0 mL of ethanol was drop cast onto the electrode surface and dried in hot air oven to form a stable layer of MWCNTs. The electro-catalytic activity of the modified electrode towards the oxidation of Trp was thoroughly investigated. The modification with MWCNTs has greatly improved the current sensitivity of CPE for the oxidation of Trp. A very minimal amount of the modifier was required to achieve such a high sensitivity. The field emission scanning electron microscopy (FESEM) images revealed a uniform coverage of the surface of CPE by MWCNTs. Nyquist plots revealed the least charge transfer resistance for the modified electrode. The analytical performance of the modified electrode was examined using amperometry under hydro-dynamic conditions. The two linear dynamic ranges observed for Trp were 0.6–9.0 μM and 10.0–100.0 μM. The amperometric determination of Trp did not suffer any interference from other biomolecules. The detection limit of Trp at modified electrode was (3.30 ± 0.37) × 10 −8 M ( S / N = 3). The analytical applications of the modified electrode were demonstrated by estimating Trp in the spiked milk and biological fluid such as blood serum. The modified electrode showed good reproducibility, long-term stability and anti-fouling effects.

An amperometric sensor based on ionic liquid and carbon nanotube modified composite electrode for the determination of nitrite in milk

Abstract: A novel carbon composite electrode has been fabricated using ionic liquid n-octylpyridinum hexafluorophosphate (OPFP) and single-walled carbon nanotube (SWCNT). This electrode combined the advantages of ionic liquid and SWCNT as well as the characteristics of the “bulk” composite electrodes. Compared with the commercial glassy carbon electrode (GCE) and the ionic liquid–graphite (IL-G) composite electrode, the ionic liquid–SWCNT (IL-SWCNT) composite electrode exhibited remarkable increase in the electron transfer rate for electroactive compound and significant decrease in the overpotential for the oxidation of nitrite. Based on the enhanced electrocatalytic activity for the oxidation of nitrite, a wide linear range from 1.0 μM to 12.0 mM with a low detection limit of 0.1 μM was obtained. Furthermore, the IL-SWCNT electrode was applied to determine nitrite levels in milk samples. Experimental results showed that the proposed electrode could be used as an effective and sensitive sensor for the determination of nitrite.

Amperometric nonenzymatic determination of glucose based on a glassy carbon electrode modified with nickel(II) oxides and graphene

Abstract: We have developed a stable and sensitive nonenzymatic glucose sensor by modifying a glassy carbon electrode (GCE) with a composite incorporating nickel(II) oxides and reduced graphene. The oxides were generated by directly electrodepositing nickel on the GCE with a graphene modifier using a multi-potential pulse process, and then oxidizing nickel to nickel(II) oxides by potential cycling. In comparison to the conventional nickel(II) oxides-modified GCE, this new nickel(II) oxides-graphene modified GCE (NiO-GR/GCE) has an about 1.5 times larger current response toward the nonenzymatic oxidation of glucose in alkaline media. The response to glucose is linear in the 20 μM to 4.5 mM concentration range. The limit of detection is 5 μM (at a S/N of 3), and the response time is very short (<3 s). Other beneficial features include selectivity, reproducibility and stability. A comparison was performed on the determination of glucose in commercial red wines by high-performance liquid chromatography (HPLC) and revealed the promising aspects of this sensor with respect to the determination of glucose in real samples.

Glucose oxidase enzyme inhibition sensors for heavy metals at carbon film electrodes modified with cobalt or copper hexacyanoferrate

Abstract: Electrochemical enzyme sensors prepared from cobalt or copper hexacyanoferrate modified carbon film electrodes plus glucose oxidase (GOx) immobilised by crosslinking with glutaraldehyde were successfully applied to the determination of heavy metal cations using fixed potential amperometry. Sensor performance was optimised with respect to the applied potential and influence of pH of the electrolyte solution. Cadmium, cobalt, copper and nickel ions were detected in the presence of fixed amounts of glucose, and the response to glucose was tested in the absence and presence of a fixed concentration of inhibitor. Electrochemical impedance spectroscopy was used for the first time to characterise the response of glucose biosensors in the presence of the inhibitors. The enzyme inhibition mechanism is reversible and competitive and 10% enzyme inhibition was achieved with submicromolar or micromolar concentrations of the metal cations.

One-pot preparation of glucose biosensor based on polydopamine-graphene composite film modified enzyme electrode

Abstract: A green, facile and low cost approach was developed to fabricate a glucose biosensor based on polydopamine–graphene hybrid film modified glucose oxidase enzyme electrode. Dopamine, graphene oxide and glucose oxidase were mixed and casted on Au electrode, and after electrochemical processing, polydopamine, glucose oxidase and graphene modified electrode was obtained. The as-synthesized enzyme electrodes were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared and X-ray diffraction spectra. The biosensor showed the excellent amperometric biosensing performances, e.g., a high detection sensitivity (28.4 μA mM−1cm−2), a low limit of detection (0.1 μm), a short response periods (

Disposable Amperometric Glycated Hemoglobin Sensor for the Finger Prick Blood Test

Abstract: The analysis of glycated hemoglobin (HbA1C) content in blood samples is crucial for the diagnosis of diabetes, and it still demands to practically use plenty of a blood sample and a complicated procedure. Hence, we report the development of a disposable amperometric HbA1C sensor for the finger prick blood test through a simple treatment of a drop of blood. To fabricate the sensor probe, the conducting polymer, poly(terthiophene benzoic acid) (pTTBA), was electrochemically grown onto the gold nanoparticles (AuNPs) coated-screen printing electrode, followed by the covalent attachment of aminophenyl boronic acid (APBA) to pTTBA as a host to capture HbA1C in the sample. The catalytic reduction response of hydrogen peroxide by HbA1C itself captured on the sensor probe was monitored as an analytical signal. The experimental parameters for the HbA1C analysis were optimized in terms of concentration of H2O2, pH, temperature, applying potential, and interferences. Under the optimized conditions, the linear dynamic range of HbA1C by amperometry was determined to be from 0.1 to 1.5% and the detection limit was to be 0.052 ± 0.02%. The reliability of the proposed HbA1C sensor was evaluated through the comparison of the results among the conventional method, the impedance method, and the proposed amperometry using a drop of a human peripheral blood sample.