ABSTRACT
Propolis is a kind of quality health foodstuff containing flavonoids, which is an important clinical effective component in many Chinese traditional medicines. The flavonoids could be used to reduce or clear free radicals, which manifests its medical functions. But there are no satisfactory methods to analyze the content of flavonoids in propolis. This paper reports a new method to determine the total effective value of flavonoids in propolis based on quenched effect for iodide-catalyzed electrochemiluminescence of luminol. It is a sensitive and simple method and might be a probable approach to examining the quality of propolis products.
Subject(s)
Electrochemical Techniques/methods , Flavonoids/analysis , Luminescent Measurements/methods , Propolis/chemistry , Catalysis , Flavonoids/chemistry , Hydrogen-Ion Concentration , Iodides/chemistry , Luminescent Agents/chemistry , Luminol/chemistry , Reproducibility of ResultsABSTRACT
Glutathione is an important active substance in organisms. Its study and determination are very significant to human being's health and life. In neutral medium, the quenching effect of reduced glutathione on the electrochemiluminescence of luminol-iodide was studied in this paper. Therefore a novel sensitive method for the determination of reduced glutathione was developed based on it. The linear response range of this method is from 3.38 x 10(-13) mol x L(-1) to 4.72 x 10(-3) mol x L(-1). This method is the most sensitive one and its linear range is the widest among those reported in the literature.
Subject(s)
Electrochemical Techniques/methods , Glutathione/analysis , Luminescent Measurements/methods , Glutathione/chemistry , Models, Chemical , Molecular Structure , Oxidation-Reduction , Reproducibility of ResultsABSTRACT
The indium tin oxide(ITO) glass was applied as the electrode to study the electrochemilumuinescent behavior of luminol on its surface. The experimental results indicated that it was an excellent electrode material for ECL of luminol with very high sensitivity. The detection limit of the luminol is as low as 10(-15) mol x L(-1) order of magnitude. Compared with the voltammetric behavior of luminol, it was revealed that both the two oxidation processes of luminol led to the emission of ECL on the surface of ITO glass,which was different from the ECL behavior of luminol on platinum electrode. Although the ECL intensity of first step oxidation of luminol was relative weak than that of the second step oxidation, it was profitable because it was a reversible process and more stable. It might be useful to fabricate the flow-cell of ECL based on its ECL activity and transparence for light. The influences of the electric parameters and the dissolved oxygen on luminol's ECL on the ITO glass, and the mechanism were also studied in the present paper.
ABSTRACT
The effect of Cu(II) ions on dopachrome has been studied by means of UV-Vis spectra in buffer solution at pH 6.5. Cu(II) ions markedly accelerated the rate of bleaching of dopachrome (DC) at 475 nm and simultaneously exhibited general absorption in the range of 300-800 nm in the system with oxygen removed by bubble nitrogen gas. The experimental results revealed that Cu(II) ions catalyzed not only the rearrangement of DC to yield mainly 5 ,6-dihydroxyindole-2-carboxylic acid (DHICA) on first-order kinetics with respect to DC in the first part of the reaction, but also the reaction of 5,6-dihydroxyindole (DHI) and DHICA to form indole-5, 6-quinone (IQ) and indole-5,6-quinone-2-carboxylic acid (IQCA), which would immediately polymerize to yield melanin.
Subject(s)
Indolequinones/chemistry , Indoles/chemistry , Ions/chemistry , Animals , Contraindications , Electrochemistry , Melanins/chemistry , Quinones/chemistry , Spectrophotometry, Ultraviolet , Spectrum AnalysisABSTRACT
A new spectrophotometric method was developed for the determination of vanadium(V). The method was based on the formation of tungstovanadophosphate-3,3',5,5'-tetramethylbenzidine-N-propanesulfonic (TMBPS) charge transfer complex. The spectrophotometric measurements were directly carried out at 450 nm and the apparent molar absorptivity was 2.74 x 10(4) L.mol-1cm-1. The linear range of the determination was 0.02-1 microgram.mL-1. The sensitivity was enhancement with a flotation-extraction preconcentration method and the apparent molar absorptivity was 3.10 x 10(5) L.mol-1cm-1.
