Kousuke Kusuda

Electrochemical investigation of thin films of cobalt phthalocyanine and cobalt-4,4′,4″,4′″-tetracarboxyphthalocyanine and the reduction of carbon monoxide, formic acid and formaldehyde mediated by the Co(I) complexes

Abstract Cyclic voltammetric investigations of thin films of cobalt(II) phthalocyanine( 1 ) and cobalt(II)-4,4′,4″,4′″-tetracarboxyphthalocyanine( 2 ) in N 2 -saturated 1 M sulfuric acid solution revealed that both compounds gave irreversibly semi-stable reduction products, R- 1 and R- 2 , at around −0.70 V vs sce . Reductions of CO, formaldehyde and formic acid by R- 1 or R- 2 were conducted with vibrating carbon fiber electrode ( cfe ) modified with 1 or 2 . Products of the reduction of CO were mainly formaldehyde and a small amount of methanol. In the reduction of CO, R- 2 / cfe was ca 17 times more efficient than R- 1 / cfe , which was however more efficient than the former in the reduction of formaldehyde. Reduction of formic acid by R- 2 and R- 1 seemed to be difficult under the conditions. Reduction of CO on the 2 / cfe polarized with rectangular potential pulse (−0.659 V for 5s and 0.20 V vs Ag/AgCl for 85s) produced nearly quantitative yield of formaldehyde and small amount of methanol.

Electrochemical behaviour of α-tocopherol in a thin film of Nujol, a model of adipose tissue

Abstract It has been shown that cyclic voltammetry (CV) on a paste electrode, made of graphite powder and an electroinactive oily material containing a redox active compound, in an aqueous electrolytic solution provided a well-defined cyclic voltammogram of the compound. The electrochemical oxidation of α-tocopherol ( I ) in the Nujol component of a Nujol carbon paste electrode (CPE) produced both dienone cation ( III ) and α-tocopherylquinone ( V ), which increased on repeated cyclic voltammograms. One-electron oxidation of I took place during a positive sweep in the potential region between 100 and 300 mV/SCE. Subsequent oxidation to cation III took place in the more positive potential region. These results were obtained using a series of CVs with increasing positive switching potentials (PSPs). CV curves of I at high concentrations in Nujol indicated that (1) the ring-opening reaction of III to produce V takes place in lower ratio than at low concentrations, and (2) the amount of I which is involved in the electrochemical reaction is inversely proportional to the concentration of I in the Nujol component of the CPE. The observed phenomena are discussed on the basis of the mobility of counter-ions in Nujol.

Cyclic voltammetry of lipophilic compounds in oil: Direct determination of lipid peroxide with a carbon past electrode

In preliminary experiments, we demonstrated that a cyclic voltammogram of a lipophilic compound can be conveniently obtained with the past electrode that was made from graphite powder and an oil in which the compound is dissolved. This finding was applied to the direct determination of lipid peroxides. Oxygenation of lipids at 120°C was followed by the cathodic current created by the reduction of the peroxides. The validity of the method was investigated by comparison with conventional methods (peroxide value, thiobarbituric acid, and weight gain). The amount of peroxides in an oil and its cathodic current show a linear relation in the initial stages of peroxidation (ca. 12 h). This electrochemical method was applied successfully to the evaluation of the antioxidant activity of butylated hydroxytoluene in linseed oil.

Direct survey of redox active compounds in sesame oil by cyclic voltammetry—studies on sesaminol, sesamol and hydroxyhydroquinone in nujol

Abstract The redox behaviour of compounds in sesame oil was investigated directly by cyclic voltammetry (CV) in 1 M sulfuric acid. The oil was used as a pasting material for a carbon paste electrode (CPE). CV curves measured on the CPE showed the redox behaviour of redox active compounds to be more concentrated than ca. 0.01%. The characteristic CV curve of sesame oil has been attributed to the reactions of sesaminol and sesamol. Electrochemical oxidation of sesaminol and sesamol in 1 M sulfuric acid took place at the methylenedioxy and para-hydroxy groups, affording substituted and unsubstituted hydroxybenzoquinones. Mechanisms for the electrochemical reactions are proposed on the basis of the behaviour of model compounds.

Analysis of traces of polycyclic aromatic hydrocarbons by adsorption on cobalt phthalocyanine and barium salts of sulphophthalocyanines followed by thermal desorption gas chromatograph

Abstract Small amounts of polycyclic aromatic hydrocarbons (PAHs) in aqueous solution were almost completely adsorbed on barium salts of copper (II) sulphophthalocyanines and cobalt (II) phthalocyanine, which were precipitated from the solution. Recoveries of the PAHs from the precipitates by thermal desorption gas chromatography were 71–95%. The method is useful for the concentration and analysis of medium molecular weight, thermally stable PAHs.

Antioxidant Activity of Polymers Bearing Hindered Phenolic Groups

Abstract Polyallylamine and polystyrene beads were allowed to react with 3,5-dibutyl-4-hydroxybenzaldehyde (BHB) and t-butylhydroquinone (BHQ), respectively. The polymeric products, poly-Aa(BHB) and polySt(BHQ) beads worked functionally as antioxidants. The antioxidant effect of the polymer beads in the oxidation of linoleic acid suspensions was investigated by both the ferric thiocyanate and thiobarbituric acid methods. The antioxidant activity of poly-St(BHQ) beads was higher than that of poly-Aa(BHB) ones. It was found that the antioxidant activity for 2 mg of 3, 5-dibutyl-4-hydroxytoluene (BHT) corresponded to that for 11.7 g of poly-Aa(BHB) and that of 0.6 g of poly-St(BHQ). The polymer beads are potential antioxidants for foods since their separation from a food oil after their use is easy because of their insolubility.

Cholesterol-lowering activity of linear- and gel-type sodium polyacrylate as dietary fiber models

Effects of linear- and gel-type (cross-linked) sodium polyacrylate and partially desalted sodium polyacrylates on serum cholesterol levels were investigated in rats fed cholesterol-free diets. Gel-type sodium polyacrylate had the lowest serum cholesterol concentration among the experimental groups. In the case of partially desalted gel-type sodium polyacrylate, the serum cholesterol-lowering effect was not found. It was thought that the water-holding capacity caused the cholesterol-lowering activity. The linear-type sodium polyacrylate and partially desalted ones reduced the serum cholesterol levels significantly (P < 0.05). The effects of the degree of polymerization of linear-type sodium polyacrylates on serum cholesterol levels were observed, but the differences among them were not significant (P < 0.05). In the case of linear-type sodium polyacrylate, their viscosity was more effective on cholesterol lowering than water-holding capacity was. Diets of 1% sodium polyacrylates did not approximately affect the body weight gain and visceral organ weight.