Catalytic Effect Of Copper Research Articles

The Continuous-Addition-of-Reagent Technique in Catalytic Kinetic-Based Determinations

Abstract A straightforward, inexpensive continuous-addition-of-reagent (CAR) system described elsewhere was applied to kinetic-catalytic analyses. The catalytic effect of copper(l1) on the oxidation of 4,4′-dihydroxybenzophenone thiosemicarbazone (DBPT) by hydrogen peroxide was exploited for this purpose. The reaction was developed by continuously adding DBPT to the reaction vessel containing the other ingredients of the catalytic reaction. The results obtained show the proposed CAR method to surpass its conventional counterpart, and its suitability for the determination of copper in serum samples.

Use of a trinitrobenzenesulphonate electrode for the kinetic determination of copper(II) and reducing sugars

The trinitrobenzenesulphonate ion-selective electrode was used for the kinetic determination of reducing sugars. The electrode was also used for the determination of rate constants and activation energies. The catalytic effect of copper(II) on the reaction of trinitrobenzenesulphonate and sulphide in alkali solution was used for the kinetic determination of the cation in the range 1–30 µg ml–1.

Thermo-oxidative stability of polyethylene in the presence of ortho-cresol novolak

Ortho-cresol novolak has been used as a thermo-oxidative stabilizer for low density polyethylene. The antioxidant shows good thermal stability and its efficacy has been studied by measuring oxidation induction time by the Differential Thermal Analysis technique. The polymer exhibits increasing stability with increasing concentration of stabilizer, following first order kinetics. The rate of inhibited oxidation, determined by Differential Scanning Calorimeter, is found to be inversely proportional to the concentration of the antioxidant, suggesting a hydrogen abstraction termination mechanism. The catalytic effect of copper has been demonstrated for the stabilized polymer and the Arrhenius plot of the air oven-ageing behavior is observed to be linear between 150°C and 190°C with a projected life of 600 h at 105°C. The additive has no influence on the electrical, mechanical and physical properties on the oxidizable substrate.

Study of the enhanced oxidative degradation of polymer films at polymer/copper (oxide) interfaces using depth profile and inert marker techniques

The degradation of poly(ester imide) films on metal substrates was monitored by determining the changes in polymer film thickness using x-ray photoelectron spectroscopy combined with ion sputter depth profiling. Thin films (1000–7000 Å) of poly(ester imide) wire enamel were spin coated onto metal substrates and aged in air at 200 °C for several hours. For films on copper substrates, thermal oxidative degradation of the polymer led to thinning of the film (2.5–3 Å/min), whereas films on aluminum substrates did not exhibit a decrease in thickness. The catalytic effect of copper upon the degradation of the polymer occurs primarily at the copper (oxide)/polymer interface, as revealed by the location of an inert gold marker layer within the polymer film before and after aging.

Catalytic effect of copper on oxidation of petroleum oil with additves

Catalytic effect of copper on oxidation of petroleum oil with additves

Kinetic determination of copper(II) by its catalytic effect on the atmospheric oxidation of 1,3-cyclopentanedione bis(4-methylthiosemicarbazone) monohydrochloride

The kinetic method is based on the catalytic effect of copper(II) on the atmospheric oxidation of 1,3-cyclopentanedione bis(4-methylthiosemicarbazone) monohydrochloride. The reaction is followed spectrophotometrically at 390 nm. The kinetic parameters of the reaction are reported and a rate equation is suggested. The calibration graphs are linear in the range 0.05–0.5 μg Cu ml −1. Interference by other ions is studied.

Reaction-rate determination of Cu(II) by use of a very simple monitored thermometric technique based on the action of this cation on the decomposition of hydrogen peroxide

A very simple and sensitive kinetic monitored thermometric technique is used for Cu(II) determination in the range 0.02–0.25 ppm. The method is based on the catalytic effect of copper(II) on the decomposition of hydrogen peroxide. The reaction is followed by measuring the rate of increase of temperature. The method suffers littleinterference.

Kinetic-spectrophotometric determination of Cu(II) and pyridine by use of the aerial oxidation of dimedone bisguanylhydrazone

The synthesis and analytical properties of dimedone bisguanylhydrazone (DIBG) are described for the first time. DIBG is oxidized by aerial oxygen and the reaction is catalysed by copper(II). The catalytic effect of copper(II) is increased by the presence of pyridine. Kinetic methods are described for determining trace amounts of copper(II) and pyridine. The reaction is followed spectrophotometrically by measuring the rate of change of absorbance at 550 nm. The calibration graphs are linear in the range 0.6–9.5 μg for copper(II) and 0.2–8.8 mg for pyridine. The methods have been applied to the determination of copper in galena and of pyridine in piperidine and isoamyl alcohol. The kinetic parameters of the reaction have been determined.

Kinetic determination of traces of copper(ii) by its catalytic effect on the oxidation of 4,4'-dihydroxy-benzophenone thiosemicarbazone by hydrogen peroxide

The kinetic method is based on the catalytic effect of copper(II) on the oxidation of 4,4'-dihydroxybenzophenone thiosemicarbazone by hydrogen peroxide. The reaction is followed spectrophotometrically at 415 nm. The kinetic parameters of the reaction are reported and a rate equation is suggested. Three methods of rate measurement are compared. The calibration graphs are linear in the range 10–90 ng Cu ml -1. There are few interferences. The method is applied to the determination of copper in waters.

Effect of iron and copper ions on the formation of nitrogen compounds in biacetyl/?-amino-acid model systems

Deep fat frying of foods with different moisture levels in different metallic containers imparts various aromas. The effect of metals, viz. iron and copper, in trace amounts (10 ppm) in biacetyl/α-amino acid model systems heated at 180 °C and 0–80% moisture levels on the formation of heterocyclic nitrogen compounds was studied. Biacetyl-glycine systems gave 2-methylpyridine and three pyrazines,dl-alanine formed three pyrazines and isoleucine formed two pyrazines. The catalytic effect of copper was greater compared with that of iron. The effect of metallic ions was very much enhanced in low-moisture systems, particularly in the formation of tetramethylpyrazine.

Catalytic effect of copper on the hexacyanoferrate(III)—cyanide redox reaction—II catalytic determination of copper

A catalytic method for the determination of copper, based on the catalysis of the hexacyano-ferrate(III)—cyanide redox reaction, is proposed. Experimental conditions to achieve the lowest detection limit are selected from the kinetics of both the catalysed and the uncatalysed reactions. The experimental measurements can be made at room temperature without close control. The rate-constant method is the most sensitive and precise, whereas the fixed-concentration and fixed-time methods appear to be the most rapid for routine analysis. A detection limit of 1.3 ng/ml and a coefficient of variation of about 3% for the determination of 63 ng/ml can be achieved. The catalytic effect of copper seems to be highly specific. Lead(II), bismuth (III), antimony (III), iron (II), iron(III), chromium(III), lanthanum(III), cerium(III), titanium(IV), zirconium(IV) and uranium(VI) interfere by precipitation. Species such as tin(II), cobalt(II), manganese(II), sulphite and thiosulphite cause serious interference because they react with hexacyanoferrate(III). Chromate interferes by its colour. Suitable methods to avoid the interferences from antimony(III), iron(III), chromium(III), titanium(IV), zirconium(IV), uranium(VI) and chromate are proposed.

Catalytic effect of copper on the hexacyanoferrate(III)-cyanide redox reaction—I: The uncatalysed and catalysed reactions

A kinetic study of the hexacyanoferrate(III)-cyanide redox reaction has been made in connection with development of a new catalytic method for copper. The reaction kinetics change with time from first- to second-order dependence with respect to hexacyanoferrate(III). The reaction is nearly inverse first-order with respect to hexacyanoferrate(II) and first-order with respect to cyanide. The reaction shows a strong positive primary salt effect, but a very small increase in the reaction rate with temperature is found. A parallel reaction proceeds with a first-order dependence with respect to hydroxide. A tentative mechanism is proposed for the first reaction, involving the formation of cyanogen radicals. The second reaction corresponds to the well-known decomposition of hexacyanoferrate(III) in alkaline medium. The catalysed reaction exhibits similar kinetics with respect to hexacyanoferrate(II) and (III) but is zero-order with respect to cyanide and hydroxide and first-order with respect to catalyst. The proposed mechanism involves two consecutive interactions of the hexacyanoferrate(III) with copper(I) and with copper(II) cyanide complexes respectively, followed by a 2-electron oxidation of a co-ordinatively bridging cyanide group.

Kinetic microdetermination of copper in urine, thiosulfate, nitrilotriacetic acid, and ethyleneglycolbis (2-aminoethylether)-NNN'N'-tetraacetic acid

An automatic spectrophotometric kinetic method is described for the ultramicrodetermination of copper. The method is based on the catalytic effect of copper(II) on the periodate-thiosulfate reaction. The method is also used for the determination of nitrilotriacetic acid (NTA) and ethyleneglycol-bis(2-aminoethylether)-NNN'-N'-tetraacetic acid (EGTA), on the basis of their inhibitory effect on the copper-catalyzed periodate-thiosulfate reaction, and of thiosulfate. The time required for the reaction to consume a fixed amount of periodate is measured automatically and related directly to the catalyst or inhibitor or substrate concentration. Ultramicroamounts of copper, NTA and EGTA, in the 10−7−10−6M level, and microamounts of thiosulfate in the 10−4−10−3M level were determined with relative errors of about 2%. The method has been applied to the determination of copper in urine.

Catalytic effect of copper(II) ions on reactions with potassium hexacyanoferrate(III)

Catalytic effect of copper(II) ions on reactions with potassium hexacyanoferrate(III)

Studies on the Sulfur-containing Chelating Agents. XXXI. Catalytic Effect of Copper (II) Ion to Formation of Mixed Disulfide

In order to discuss the possibility of the contribution of the chelating ability to the radioprotective activity in cysteamine, effects of copper (II) ion to the formation of the mixed disulfide was investigated in the systems of cysteamine and cysteine, glutathione and albumin respectively as the reactions between two kinds of thiol compound and in the system of cystamine and cysteine as the reaction between disulfide and thiol compound by the use of 35S-cysteamine or 14C-cysteine. Separations of the mixed disulfides were achieved by electrophoresis and amounts of the mixed disulfides were estimated by the measurement of radioactivity. Remarkable catalytic effects were observed depending upon the reaction conditions. Whereas inhibitive effects were observed in some cases. Relationship between the effect of copper (II) ion and the reaction condition was discussed and an intermediate copper chelate was presumed for the reaction mechanism.

COPPER AND ANEMIA

Steenbock, Hart and their co-workers have made a series of systematic investigations on the catalytic effect of copper on hemoglobin formation. In Europe a great part of any interest in the present article would be due to the fascinating history of this important discovery. In America, no doubt, all pediatricians are familiar with the facts which led to this contribution to science; however, I shall make a brief survey of these investigations, because sometimes discoveries are not as well known in the country in which they are made as abroad. Let me thus begin with the transport of owls to Athena. The subject of these investigations was interesting to pediatricians, as it dealt with the nutritional anemia due to the exclusive feeding of milk. In the first period of the investigations, rabbits from 4 to 5 weeks of age were placed on a milk diet. After five or six weeks