Flow Injection Determination of Glutamate in Human Serum and Rat Brain Samples with Immobilized Glutamate Oxidase and Glutamate Dehydrogenase Reactors

Peer Reviewe

Reagentless enzyme electrode for malate based on modified polymeric membranes

Abstract A series of polymeric membranes have been employed as outer barriers in an amperometric malate dehydrogenase (MDH)/diaphorase (DI) or MDH/DI/NAD + /mediator enzyme electrode for the determination of malate in undiluted neutral or acidic media. MDH/DI were physically entrapped with NAD + and mediator in a mixed ester cellulose membrane. Outer membranes such as non-anionic surfactant-modified cellulose acetate/Tween-80 and unplasticised spin coated PVC/polycarbonate (PC) resin in conjunction with an ascorbate oxidase (AOD) layer were utilised. Mechanical strength, thickness studies and diffusional properties of the membranes were investigated. Hexacyanoferrate(III), 2,4-dichlorophenolindophenol (DCPI) and naphthoquinone (NQ) were tested as mediators for enzymatically produced NADH using cyclic voltammetry. Analytical utility of the sensors is demonstrated

Determination of ionic and organically bound zinc in the sperm of the sea urchin by atomic absorption spectrophotometry

A method of extraction and assay of Zn in the sperm of sea urchin is developed. Three different extraction reagents are used in order to differentiate the fractions of the differently bound Zn in the sperm. The determination of concentration of Zn was made by atomic absorption spectrophotometry after constructing working curves with standard solutions of Zn. © 1977

Chemical constituents of rubus ulmifolius schott

From the leaves of Rubus ulmifolius Schott, quercetin, kaempferol, trifolin (kaempferol-3-0-galactoside), hyperin (quercetin-3-0-galactoside), chlorogenic acid, caffeic acid, a kaempferol-3-0-caffeoyl-ester, and a glucose-caffeoyl ester were isolated and identified. Free fatty acids were characterised by gas chromatography of their methyl esters. © 1981 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted

Kinetic study of the chemical behavior of quercetin and Kaempferol in alkaline media

In this work the kinetics of the oxidation of two flavonols in alkaline medium have been studied. The fluorescence of quercetin and kaempferol has been monitored by a fluorimetric technique after the addition of an alkaline buffer to their alcoholic solutions. The pH, at which the rate of their fluorescence decrease has its maximum, was 11.0. The oxidation of the two flavonols in alkaline medium follows a first order kinetic. The reaction rate constants of this reaction are 27.5×10-3 sec-1 and 1.22×10-3 sec-1 for quercetin and kaempferol respectively. Working curves in the range of 2.5-25 μM for the determination of the two flavonols, based on the rate of their fluorescence decrease in alkaline medium, have been constructed and a kinetic method was developed. © 1983 Springer-Verlag

Isolation of quercetin and kaempferol from Rubus ulmifolius and their fluorometric assay

A fluorometric method for the determination of the flavonols quercetin and kaempferol in the leaves of Rubus ulmifolius was developed. A chromatographic technique for the isolation and separation of the two compounds was described. Working curves with standard solutions of quercetin and kaempferol at pH 2.5 were constructed. The effect of pH on the fluorescence intensity was studied with fluorescence measurements in acidic solutions of the compounds. The wavelengths for all fluorescence measurements were selected from fluorescence spectra of the two compounds. © 1982

Kinetic study and analytical application of the iodate-arsenite reaction in strongly acidic solutions

The iodate-arsenite reaction in strongly acidic solutions was studied by stopped-flow spectrophotometric techniques. The molar absorptivity of iodine and the activation energy of the reaction were determined. A method for determining arsenite was developed on the basis of this reaction. The method was checked in the concentration range 5.0·10-4-1.0·10-2 M, the mean error being about 3%. © 1974

Kinetic study and analytical application of the iodate-arsenite reaction in strongly acidic solutions

The iodate-arsenite reaction in strongly acidic solutions was studied by stopped-flow spectrophotometric techniques. The molar absorptivity of iodine and the activation energy of the reaction were determined. A method for determining arsenite was developed on the basis of this reaction. The method was checked in the concentration range 5.0·10-4-1.0·10-2 M, the mean error being about 3%. © 1974