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Amperometric enzyme electrode for aerobic glucose monitoring prepared by glucose oxidase immobilized in poly(vinylferrocenium)

Abstract A simple, sensitive, stable and low-cost glucose sensor with a fast response that operates under aerobic solution conditions is described. The electrode consists of a polyvinylferrocenium-perchlorate-coated Pt surface onto which the enzyme is attached. The current response of the electrode was determined by measuring either cyclic voltammetric peak current values or steady state current values obtained after a constant-potential step. The effects of glucose concentration, the amount of enzyme immobilized, the thickness of the polymeric layer and the operating temperature on the response of the enzyme electrode were studied. The effects of two common physiological sources of interference were also investigated. A mechanism for the operation of the electrode is also proposed.

Amperometric enzyme electrode for sucrose determination prepared from glucose oxidase and invertase co-immobilized in poly(vinylferrocenium)

Abstract Co-immobilization of two enzymes, glucose oxidase and invertase, in polyvinyl(ferrocenium) perchlorate (PVF + ClO − 4 ) film led to the development of a simple, sensitive, stable and low-cost sucrose sensor. Invertase catalyses the conversion of sucrose to α-glucose and β-fructose. Phosphate ions used in the medium catalyse the conversion of α-glucose to β-glucose, eliminating the need for the commonly used third enzyme, mutarotase, for mutarotation. Glucose oxidase catalyses the oxidation of β-glucose to gluconic acid, producing H 2 O 2 . Current due to H 2 O 2 oxidation catalysed by PVF + centres was measured, in contrast to most existing sucrose electrodes, which rely on measurement of the O 2 reduction current.

Amperometric enzyme electrode for organic peroxides determination prepared from horseradish peroxidase immobilized in poly(vinylferrocenium) film

Organic peroxides, t-butyl hydroperoxide, 2-butanone peroxide, cumene hydroperoxide and t-butyl peracetate, were determined by an amperometric enzyme electrode. The enzyme electrode was prepared through electrostatic immobilization of horseradish peroxidase (HRP) in a polyvinylferrocenium (PVF) film. A PVF(+)ClO(4)(-) film was coated on a Pt foil at +0.70 V by electrooxidation of polyvinylferrocene in methylene chloride with 0.1 M tetrabutylammonium perchlorate (TBAP). The enzyme modified electrode PVF(+)HRP(-) was prepared by anion-exchange in a solution of HRP(-) in 0.05 M phosphate buffer at pH 8.5. FTIR spectroscopy was used to identify PVF, PVF(+)ClO(4)(-), and PVF(+)HRP(-). The immobilized amount of the enzyme in the film was determined by UV spectroscopy. The effects of the polymeric film thickness, bulk enzyme concentration used in the immobilization treatment and the temperature on the performance of enzyme electrode were investigated. The inhibitory effect of oxygen was also examined. Linearities, lower detection limits, active life times and sensitivities of the electrode were determined for each peroxide.

Characterization of redox polymer based electrode and electrochemical behavior for DNA detection

Characterization of redox polymer, poly(vinylferrocenium) perchlorate (PVF+ClO4-) coated as a film on Pt electrodes, and the detection of DNA based on the electrochemical behavior of the polymer were described in this study. PVF+ClO4- modified electrodes were prepared by the electrooxidation of poly(vinylferrocene) (PVF), and DNA immobilized polymer modified electrode was then prepared. The characterization of the polymer modified electrodes were performed by scanning tunneling microscopy (STM), Raman spectroscopy and alternating current (AC) impedance. The effects of DNA concentration, pH, and polymer films in various thicknesses based on the electrode response were also investigated. The electrochemical behavior of DNA modified polymer electrode by using double-stranded DNA (dsDNA) or single-stranded DNA (ssDNA) was compared. DNA hybridization was also investigated.

Determination of Hg2+ on poly(vinylferrocenium) (PVF+)-modified platinum electrode.

A new surface based on poly(vinylferrocenium) (PVF(+))-modified platinum electrode was developed for determination of Hg(2+) ions in aqueous solutions. The polymer was electrodeposited on platinum electrode by constant potential electrolysis as PVF(+)ClO(4)(-). Cl(-) ions were then attached to the polymer matrix by anion exchange and the modified electrode was dipped into Hg(2+) solution. Hg(2+) was preconcentrated at the polymer matrix by adsorption and also complexation reaction with Cl(-). Detection of Hg(2+) was carried out by differential pulse anodic stripping voltammetry (DPASV) after reduction of Hg(2+). Mercury ions as low as 5 x 10(-10)M could be detected with the prepared electrode and the relative standard deviation was calculated as 6.35% at 1 x 10(-6)M concentration (n=6). Interferences of Ag(+), Pb(2+) and Fe(3+) ions were also studied at two different concentration ratios with respect to Hg(2+). The developed electrode was applied to the determination of Hg(2+) in water samples.

Electrochemical reduction of tetraphenylcyclopentadienones

Abstract The electroreduction behavior of tetraphenylcyclopentadienone (tetracyclone) and some of its m,m′-and p,p′-substituted derivatives in acetonitrile was investigated. The mechanism for the electroreduction of these compounds in the absence and in the presence of protons was proposed using the results of cyclic voltammetry and controlled potential electrolysis experiments. The effects of the substitution on the peak potentials and on the stability of the anion radicals are discussed.

Electrochemical characterization of redox polymer modified electrode developed for monitoring of adenine

Electrochemical characterization of redox polymer for monitoring of adenine was described in this study using poly(vinylferrocenium) (PVF(+)) modified platinum (Pt) electrode. Scanning electron microscope (SEM) was used for the surface characterization. The electrochemical behaviors of polymer modified and adenine immobilized polymer modified electrodes were investigated by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In order to obtain more sensitive and improved electrochemical signals, analytical parameters such as the effects of polymeric film thickness, immobilization time of adenine, pH and adenine concentration were examined on the response of the polymer modified electrode. Alternating current (AC) impedance spectroscopy was used for the characterization of polymer modified and adenine immobilized polymer modified electrodes. The effect of possible interferents on the response of the electrode was examined.

ELECTROCHEMICAL IBTERACTIOS OF BEYPAZARI LIGNITE IS STROHG ACIDIC MED1A

ABSTRACT Beypazari lignite was extracted with acetonltrile and acetonitrile/HClO4 and electrochemical hydrogenation of the lignite in acetonltrile/LlC104 in the presence of HClO4. was investigated. Controlled potential electrolysis experiments were carried out at -0.5 V vs a Ag/AgCl electrode. Infrared spectra of the products were measured and yields of extraction were determined. Extraction yields In acetonitrile and acetonitrile/HCIO4 were 9 and 17.3 %, respectively. The yield of extractable material did not increased in the electrochemical environment. Acetonltrile extraction produced residual matter with less hydroxyl groups. Stirring the lignite in acetonitrile(HClO4 for 7 hours oxidized both the extract and the residue. The residue seemed to contain less hydroxyl groups than that of the acetonltrile extraction residue and It has new carbonyl and etheric groups that were absent in the original lignite. It was found that the material extracted during electrochemical treatment by acetonitrile/HClO4 was...

Electro-oxidation behaviour of some methoxyanthracenes in benzonitrile

Abstract Electro-oxidation behaviour of 9,10-dimethoxy- and 9-cyano-10-methoxyanthracenes on a Pt electrode was investigated in benzonitrile containing tetra- n -butylammonium perchlorate using controlled potential electrolysis, cyclic voltammetry and ESR spectroscopy. The concentration of protons produced during electro-oxidation was determined spectroscopically. Anthraquinone was found to be the major product of electro-oxidation of these two compounds.