A method for sensitive and selective determination of silver based on the catalytic effect of silver(I) ion on the oxidation of Janus Green by peroxodisulfate is described. o-Phenanthroline is used as an activator. The rate of the decrease in absorbance of Janus Green (at 615 nm) is proportional to the concentration of silver in the range of 0.3-4.0 ng mL(-1) and 4.0-500.0 ng mL(-1). The theore...

A molecularly imprinted polymers based electrochemical sensor was fabricated by electropolymerizing pyrrole on a Fe3O4 nanoparticle modified glassy carbon electrode. The sensor showed highly catalytic ability for the oxidation of 2,4-dichlorophenol (2,4-DCP). Square wave voltammetry was used for the determination of 2,4-DCP. The oxidation peak currents were proportional to the concentrations of...

A simple, rapid and sensitive flow injection spectrophotometric method for determination of selenium (0.005-1.5 mug ml(-1)) is described. The method is based on the catalytic effect of Se(IV) on the reduction reaction of thionine (TN) with sulphide ion, monitored spectrophotometrically at 598 nm. The detection limit is 5 ng ml(-1) the relative standard deviation for eight replicate measurements...

An analytical method for the determination of total iodine at the ng level in urine, biological materials and foods was investigated. The organic substances were completely decomposed using a mixed solution of nitric, perchloric and sulfuric acids as pretreatment agents at ca. 230 degrees C. Iodine in the resulting solution was analyzed by a kinetic-photometric method based on the catalytic eff...

A highly simple and sensitive catalytic spectrophotometric method for the determination of tiopronin based on its inhibitory effect on the hemoglobin-catalyzed the reaction of H2O2 and acid chrome blue K(ACBK) was developed. The concentration of tiopronin is linear with the percentage inhibition (I%) of system under the optimal experimental conditions. The calibration graph is linear in range 0...

In the present study, a novel catalytic-kinetic spectrophotometric method was developed for the determination of trace amounts of copper. It is based on the catalytic effect of Cu(II) on the reduction of brilliant cresyl blue (BCB) by ascorbic acid in pH 5.0 acetate buffer medium. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of BCB at 624 nm. The ope...

1. The molecular weights of the catalytic and regulatory polypeptide chains of aspartate transcarbamylase were determined to be 33,500 and 17,000, respectively. The results of three empirical methods are in good agreement with those obtained by sedimentation equilibrium in guanidine-hydrochloride or derived from the intrinsic viscosity and the sedimentation coefficient measured in the same solv...

The intrinsic tryptophan fluorescence of Schizosaccharomyces pombe mitochondrial F1 is a very sensitive probe to differentiate nucleotide binding to catalytic and noncatalytic sites (Divita, G., Di Pietro, A., Roux, B., and Gautheron, D. C. (1992) Biochemistry 31, 5791-5798), the catalytic site saturation producing quenching of Trp-257 fluorescence (Divita, G., Jault, J.-M., Gautheron, D. C., a...