Akira Kunugi

Properties of glucose sensors based on the immobilization of glucose oxidase in N-substituted polypyrrole film

Abstract Amperometoric glucose sensors were prepared by the electropolymerization of 3-(1-pyrrolyl)propionic acid (PPA) in the presence of the enzyme, following the treatment with water-soluble carbodiimide (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, EDC) to provide covalent bonding between glucose oxidase (GOD) and polypyrrole derivatives. Poly(o-phenylenediamine) (PPD) and Nafion films were introduced as the inner film in the same electrodes. The EDC treatment was effective to improve the stability of the glucose response except on the electrode with Nafion inner film. Though neither electrode was influenced by the addition of urea or d -(−)-fructose, the influence of ascorbic acid, acetaminophen and uric acid was not negligible even on the electrode with inner film.

Properties of glucose sensors prepared by the electropolymerization of a positively charged pyrrole derivative

Abstract Amperometric glucose sensors were prepared by electropolymerization of a pyrrole derivative having the positively charged group, 3-(1-pyrrolyl)propyltrimethylammonium bromide, in the presence of glucose oxidase on bare and Nafion-coated platinum electrodes. Linear relationships between the glucose concentration and the response current for the electrode with and without Nafion inner film were up to 10.0 and 6.0 mmol dm −3 , respectively. The introduction of Nafion inner film lowered the influence of electroactive compounds, such as ascorbic acid, uric acid, and acetoaminophen, on the sensor response, but was not able to eliminate the influence of these compounds sufficiently. However, Nafion inner film was effective in increasing the electrode stability. The response current of the electrode with Nafion film remained stable for more than 50 days, while that without Nafion film was significantly reduced after 20 days of use.

Preparation of glucose sensors using the Langmuir–Blodgett technique

Abstract A novel glucose sensor was fabricated using the Langmuir–Blodgett (LB) technique with a phospholipid analogous vinyl polymer, 2-[2-methacryloyloxy)ethyldimethyl-ammonium]ethyl-5β-cholesten-3-yl phosphate polymer (PCP). The ordered monolayers of PCP were easily prepared at the interface of air–aqueous solution containing glucose oxidase (GOD), and could be transferred onto the platinum wire electrode. The response current for the observed electrode was constant for 50 days, after an initial change of signal over the first few days.

The scheme of methanol oxidation at a platinum electrode in an acid solution

Abstract The scheme of methanol oxidation at a platinum electrode in a sulphuric acid solution was investigated by potential step and product-analysis methods. The potential step method revealed that dissolved formaldehyde accumulated in the vicinity of the electrode surface during methanol oxidation at potentials of about 0.6–0.8 V. Its accumulation occurred also at low methanol concentrations at which the bulk concentration of the formaldehyde was small. The rates of formaldehyde oxidation obtained and its accumulation showed that carbon dioxide was formed predominantly via dissolved formaldehyde at about 0.75–0.80 V, while at lower potentials its formation did not occur via dissolved formaldehyde. High methanol concentrations favoured the accumulation of formaldehyde in the bulk solutions.

Properties of glucose sensors prepared by the electropolymerization of pyrroles containing phosphatidylcholine (II)

New hemocompatible glucose sensors were prepared by electropolymerization of pyrrole derivatives having phosphatidylcholine, 5-(1-pyrrolyl)pentyl-2-(trimethylammonium)ethyl phosphate, in the presence of glucose oxidase (GOD), with an inner-membrane of Nafion or poly(o-phenylenediamine) (PPD). The introduction of these membranes not only eliminated the influence of ascorbic acid on the sensor response but also increased the electrode stability. The electrode responses containing PPD inner-membrane were shown to be relatively constant for more than 200 days or three times as long as the electrode responses without the inner membranes.

Electroreduction of 2-cyclohexen-1-one on metal–solid polymer electrolyte composite electrodes

The effects of the electrode material on electroreduction of 2-cyclohexen-1-one were examined using various metal–solid polymer electrolyte electrodes, i.e., unmodified, Bi-modified and Zn-modified Pt- and Au-Nafion, Bi-Selemion and Zn-modified Au-Selemion electrodes. A mixture of monomeric products such as cyclohexanone 2 and 2-cyclohexen-1-ol 3, and/or dimeric products such as the diketone 4, the hydroxyketone 5 and the glycol 6 were produced, the main products being largely dependent on electrolytic conditions. For example, modification of Pt-Nafion electrode with bismuth or zinc gave 2 selectively at high current efficiency. Modification of Au-Nafion electrode with bismuth was effective in giving dimeric products, whereas with Bi,Pt-Nafion and Zn,Pt- and Zn,Au-Nafion electrodes, only monomeric products were obtained. The use of Bi-Selemion and Zn,Au-Selemion electrodes gave preferentially dimeric products.

Electrochemical method to vinyl fluorides (II). Cathodic cleavage and carboxylation of 1-fluoro-2-(4-biphenylyl)vinyl phenyl sulphoxide in nonaqueous media

Abstract The electrolytic reduction of 1-fluoro-2-(4-biphenylyl)vinyl phenyl sulphoxide ( 1 ) in nonaqueous media involves desulphinylation, defluorination followed by reduction of the sulphinyl group, and reduction to the corresponding sulphide, resulting in the formation of 1-fluoro-2-(4-biphenylyl)ethylene ( 2 ), 2-(4-biphenylyl)vinyl phenyl sulphide ( 3 ) and 1-fluoro-2-(4-biphenylyl)vinyl phenyl sulphide ( 4 ). Distribution of these products is greatly dependent on the proton donors such as phenol, acetic acid and benzoic acid. In the absence of proton donors, the yields of products are low. The controlled potential electrolysis of 1 in N , N -dimethylformamide containing carbon dioxide was subjected to a substituting carboxylation to afford 2-fluoro-3-(4-biphenylyl)-propenoic acid ( 6 ), with concomitant formation of 2 and 3 .

Electrochemical method to vinyl fluorides—I. Cathodic elimination of 1-fluoro-2-arylvinyl phenyl sulphones in acetonitrile

Abstract The electrolytic reduction of 1-fluoro-2-arylvinyl phenyl sulphones in acetonitrile involves cleavage of carbon-sulphur and/or carbon-fluorine bonds, resulting in the formation of 1-fluoro-2-aryl-ethylenes and arylethylenes with a molar ratio of about 1:1. The coulometric n -values are about three electrons per molecule, in the presence of efficient proton donors such as phenol, acetic acid and benzoic acid, and at all the following electrodes: mercury, platinum, lead and glassy carbon. In the absence of proton donors, the yields of 1-fluoro-2-arylethylenes and arylethyelens are very low, the n -value be about 1.

Electrosynthesis of sulfur-containing organic compounds from allene derivatives using a sacrificial mixed sulfur/graphite electrode

Abstract Electrosynthesis of sulfur-containing organic compounds from cumulene derivatives was studied using a sacrificial sulfur-graphite electrode. 1,1-Di- p -chlorophenyl-4,4-diphenylbuta-1,2,3-triene ( 1a ), 1,1-di- p -chlorophenyl-4,4-di- p -methylphenylbuta-1,2,3-triene ( 1b ), 1,1,4,4-tetraphenylbuta-1,2,3-triene ( 1c ) and 1,1-di- p -methoxyphenyl-4,4-diphenylbuta-1,2,3-triene ( 1d ) were used as cumulenes. With 1a , 1b and 1c , 7-membered ring compounds with five sulfur atoms such as pentathiepins 2a , 2b and 2c were produced as the major products accompanied with dimeric compounds 3a , 3b and 3c which had a 1,2,5,6-tetrathiocin skeleton in minor amounts, respectively. However, 1d , which is the most difficult to be reduced among the cumulenes studied, did not give sulfur-containing organic compounds. Yields of 2a , 2b and 2c decreased a little by the addition of a proton donor such as benzoic acid. Main products 2 will be initiated by a Michael addition of the polysulfide anion(s) (S 8 2− and/or S 6 2− ) produced by electroreduction of elemental sulfur. By-products 3 will be probably produced by further reaction of 2 with the polysulfide anion(s).

Cathodic elimination of 1-methylthio-1-p-tolylsulphonyl-2-arylethenes in non-aqueous media

Abstract The electrolytic reduction of 1-methylthio- p -tolylsulphonyl-2-arylethenes (1) in acetonitrile and N , N -dimethylformamide involves selective cleavage of a carbon—sulphur bond, resulting in formation of (E)-1-methylthio-2-arylethenes (2) in moderate yields with the consumption of about 2 electrons per mol, in the presence of efficient proton donors such as phenol and benzoic acid and at all the following electrodes; mercury, platinum, lead and glassy carbon. In the absence of proton donors, as was expected, the yield of 2 is very low and the hydrodimerization of 1 takes place.