ascorbic-acid and ferric-ferrocyanide

Topics: Alkaline Phosphatase; Ascorbic Acid; Coloring Agents; Ions; Limit of Detection; Magnetic Phenomena; Oxidoreductases; Protons; Water

Topics: Ascorbic Acid; Beverages; Carbon; Copper; Electrochemical Techniques; Electrodes; Ferrocyanides; Limit of Detection; Nanostructures; Signal-To-Noise Ratio

In the present work, ternary mixtures of Acetaminophen, Ascorbic acid and Uric acid were resolved using the Electronic tongue (ET) principle and Cyclic voltammetry (CV) technique. The screen-printed integrated electrode array having differentiated response for the three oxidizable compounds was formed by Graphite, Prussian blue (PB), Cobalt (II) phthalocyanine (CoPc) and Copper oxide (II) (CuO) ink-modified carbon electrodes. A set of samples, ranging from 0 to 500 µmol·L

Topics: Acetaminophen; Ascorbic Acid; Biosensing Techniques; Copper; Electrochemical Techniques; Electrodes; Electronic Nose; Ferrocyanides; Graphite; Humans; Indoles; Organometallic Compounds; Uric Acid

Herein we reported Prussian blue nanoparticles (PBNPs) possess ascorbic acid oxidase (AAO)- and ascorbic acid peroxidase (APOD)-like activities, which suppressed the formation of harmful H

Topics: Ascorbate Oxidase; Ascorbate Peroxidases; Ascorbic Acid; Catalysis; Ferrocyanides; Humans; Iron; MCF-7 Cells; Nanoparticles; Oxidation-Reduction

A low-interferences enzymatic sensor for evaluating the antioxidant capacity was developed. Xanthine oxidase was used to produce superoxide radicals that spontaneously dismutate to hydrogen peroxide. Low xanthine concentrations were used to minimize the rapid dismutation of the superoxide radical before its fast reaction with antioxidants. The sensor operates in the reduction mode, and evaluations with low interferences of the antioxidant capacity are based on the detection of remaining hydrogen peroxide using Prussian blue electrodes at low potentials. The linear calibration graph is between 2 - 10 μM ascorbic acid. No interferences were observed from easily oxidisable substances including uric acid, which is produced in the enzymatic reaction or other substances usually found in foods. The method was used to evaluate the antioxidant capacity in different real juice samples.

Topics: Antioxidants; Ascorbic Acid; Calibration; Electrochemistry; Electrodes; Ferrocyanides; Food Analysis; Free Radicals; Fruit and Vegetable Juices; Hydrogen Peroxide; Linear Models; Oxidation-Reduction; Superoxides; Xanthine Oxidase

We report on the development of a nanocarbon based anode for sensing of ascorbic acid (AA). The oxidation of AA on this anode occurs at a quite low overpotential which enables the anode to be connected to a biocathode to form an ascorbic acid/O2 biofuel cell that functions as a self-powered biosensor. In conjunction with a Prussian blue electrochromic display the anode can also work as a truly self-powered sensor. The oxidation of ascorbic acid at the anode leads to a reduction of the Prussian blue in the display. The reduced form of Prussian blue, called Prussian white, is transparent. The rate of change from blue to colourless is dependent on the concentration of ascorbic acid. The display can easily be regenerated by connecting it to the biocathode which returns the Prussian blue to its oxidized form. In this way we have created the first self-powered electrochromic sensor that gives quantitative information about the analyte concentration. This is demonstrated by measuring the concentration of ascorbic acid in orange juice. The reported quantitative read-out electrochromic display can serve as a template for the creation of cheap, miniturizable sensors for other relevant analytes.

Topics: Ascorbic Acid; Bioelectric Energy Sources; Biosensing Techniques; Electrochemical Techniques; Electrodes; Equipment Design; Ferrocyanides; Oxidation-Reduction

A cost-effective, highly compact, and versatile optoelectronic device constructed of two ordinary light emitting diodes compatible with optosensing films has been developed. This fibreless device containing chemoreceptor, semiconductor light source, and detector integrated in a miniaturized flow-through cell of low microliter internal volume works as a complete photometric chemical sensor suitable for detection in flow analysis. The operation of the developed device under nonstationary programmable-flow conditions offered by sequential injection analysis has been demonstrated using Prussian Blue film as a model optical chemoreceptor. The unique spectroelectrochemical properties of the sensing material enable its use for optical sensing of redox species, whereby ascorbic acid and hydrogen peroxide have been chosen as model analytes. The reported SI-sensor system features fast and reproducible determination of both analytes in the submillimolar range of concentrations. The construction concept demonstrated in this work can be easily applied to other kinds of optical sensors based on absorbance sensing films.

Topics: Ascorbic Acid; Chemistry Techniques, Analytical; Ferrocyanides; Hydrogen Peroxide; Membranes, Artificial; Optics and Photonics; Oxidation-Reduction; Photochemistry

A micro-patterned Prussian Blue (PB) array of nanometer thickness was fabricated using soft photolithography and voltammetric deposition for electrocatalytic detection of biomolecules. A self-assembled alkylthiol monolayer on gold was photooxidized by UV irradiation with a TEM mask, generating an imprinted pattern into which a PB microarray was subsequently deposited. Cyclic voltammetric and microscopic characterization indicates that the PB arrays demonstrate improved electrochemical stability as compared to conventional PB films, particularly at neutral pH, allowing scores of potential cyclings with little film deterioration. The PB film thickness in the array can be conveniently controlled by varying deposition time. Facile electron transfer was observed on the array electrode and the effect of the SAM layer on electrochemical response was investigated. The use of PB arrays for electrocatalytic analysis of biologically significant molecules was demonstrated with ascorbic acid (AA). The calibration curve for AA shows a linear relationship over the concentration range of 1.0 x 10(-5) to 8 x 10(-7) M with a correlation coefficient of 0.99. The detection limit was determined to be 1 x 10(-8) M, which is about 100 times lower than the reported value on a conventional PB electrode. The method developed here provides a new functional surface for bioanalysis using electrocatalytic principles.

Topics: Ascorbic Acid; Catalysis; Electrochemistry; Electrodes; Ferrocyanides; Microarray Analysis; Oxidation-Reduction; Sensitivity and Specificity

Prussian blue nanowire array (PBNWA) was prepared via electrochemical deposition with polycarbonate membrane template for effective modification of glassy carbon electrode. The PBNWA electrode thus obtained was demonstrated to have high-catalytic activity for the electrochemical reduction of hydrogen peroxide in neutral media. This enabled the PBNWA electrode to show rapid response to H2O2 at a low potential of -0.1 V over a wide range of concentrations from 1x10(-7) M to 5x10(-2) M with a high sensitivity of 183 microA mM(-1) cm(-2). Such a low-working potential also substantially improved the selectivity of the PBNWA electrode against most electroactive species such as ascorbic acid and uric acid in physiological media. A detection limit of 5x10(-8) M was obtained using the PBNWA electrode for H2O2, which compared favorably with most electroanalysis procedures for H2O2. A biosensor toward glucose was then constructed with the PBNWA electrode as the basic electrode by crosslinking glucose oxidase (GOx). The glucose biosensor allowed rapid, selective and sensitive determination of glucose at -0.1 V. The amperometric response exhibited a linear correlation to glucose concentration through an expanded range from 2x10(-6) M to 1x10(-2) M, and the response time and detection limit were determined to be 3 s and 1 microM, respectively.

Topics: Ascorbic Acid; Biosensing Techniques; Carbon; Electrochemistry; Electrodes; Ferrocyanides; Glucose; Hydrogen Peroxide; Microarray Analysis; Microscopy, Electron, Scanning; Nanowires; Oxidation-Reduction; Uric Acid

The distribution of a lipophilic spin probe, 5-doxyl stearate, between the inner and outer halves of the sarcoplasmic reticulum (SR) bilayer was determined by titration with Ni X EDTA, a spin broadening agent. Titrations were also performed with Fe(CN)3-6 and with the solvated Ni2+ cation. Ni X EDTA titrations reached a clearly defined asymptote at 35% signal reduction. Fe(CN)3-6 and Ni2+ titrations gave biphasic curves but showed 35% of the signal to be readily eliminated at low concentrations. When the Ni2+ cation was used with ionophore, titrations indicated that 96% of the probe is aligned in the bilayer with the spin moiety at either the inner or outer interface. It was concluded that the spin probe distribution between the outer and inner halves of the SR bilayer is 35:65, respectively. Titrations performed on vesicles of purified SR lipids gave a ratio of 60 exposed:40 protected, consistent with the vesicular geometry. In addition the spin probe distribution in SR vesicles did not vary as a function of temperature, salt concentration, or spin probe concentration. On this basis it was concluded that the spin probe distribution gives a reasonable estimation of the volume of fluid lipids available to readily solubilize the probe in each half of the bilayer and that the observed asymmetry in distribution is due to the presence of SR proteins which were eliminated in the pure lipid vesicles. Furthermore, as EDTA is unique in its ability to chelate transition metals, Ca2+ and EGTA can be used in Ni X EDTA titrations without altering the chelation of Ni2+. Known changes in ATPase conformation accompanying Ca2+ and adenyl-5'-yl imidodiphosphate X Mg binding did not affect the spin probe distribution. However, phosphorylation of the enzyme by Pi gave a small, but clearly discernible, protection of spin probe signal. Chemical reduction with ascorbate indicated that this was due to occlusion of a small fraction of spin probes and thus possibly SR lipids.

Topics: Adenosine Triphosphatases; Adenylyl Imidodiphosphate; Animals; Ascorbic Acid; Calcium; Cyclic N-Oxides; Edetic Acid; Electron Spin Resonance Spectroscopy; Ferrocyanides; Lasalocid; Lipid Bilayers; Magnesium; Nickel; Phosphorylation; Protein Conformation; Rabbits; Sarcoplasmic Reticulum; Spin Labels; Tissue Distribution