Jingwan Kang

Plasma degradation of dyes in water with contact glow discharge electrolysis.

Contact glow discharge electrolysis (CGDE) of two dyes, weak acid brilliant red B and weak acid flavine G, was investigated under different concentrations, temperature and mediums. From the variation of their concentration with the reaction time, it was demonstrated that the oxidation would be a first-order reaction. On the base line of UV spectra of solution in the degradation process, we deduced that two dyes underwent the oxidative degradation in CGDE. The rate constants, relevant coefficients and the decolorization degree were displayed under different conditions.

Preparation of ultrafine nickel powder and its catalytic dehydrogenation activity

Nanocrystalline nickel powders were prepared from aqueous solution by reducing their corresponding metal salts under suitable conditions. The experimental conditions including the types and concentration of protective agents, feeding order and the pH of the solution that influence the average particle size were studied in detail. X-ray powder diffraction patterns show that the nickel powder is cubic crystallite. The average particle size of the ultrafine nickel powder is 50 nm. In addition, we also studied the effect of particle size in liquid phase dehydrogenation of 2-butanol. The results show that the smaller particle size is favored of increasing catalytic activity.

Spectroscopic and voltammetric studies of the cobalt (II) complex of Morin bound to calf thymus DNA

Absorption and emission spectra, viscometric and electrochemical studies have been carried out on the interaction of Morin (2′, 3, 4′, 5, 7-pentahydroxyflavone) and its Co complex, CoL2·3H2O[L = Morin (2′-OH group deprotonated)], with calf thymus DNA. In the presence of DNA, the complex exhibits a hypochromism in the u.v.–vis. spectra and a large enhancement in emission spectra suggests that the complex binds to DNA via a weak partial intercalation, revealed by competitive experiments, viscosity and by electrochemical studies. The binding constant is ca. 2 × 103 M−1 at 20 °C. Both ZnL2·3H2O and CoL2·3H2O complexes have the same molecular structure, ZnL2·3H2O shows the spectral characteristics and electrochemical behaviour which agrees with observations for other intercalators in the presence and absence of DNA, whereas the CoL2·3H2O complex shows different spectral characteristics and electrochemical behaviour to that of ZnL2·3H2O, which suggests that the mode and affinity of the complex CoL2·3H2O binding to DNA are different from that of ZnL2·3H2O. Both ZnL2·3H2O and CoL2·3H2O complexes exhibited different antitumour activity. So the binding mode and affinity of complexes to DNA may play an important role in determining the antitumour activity.

INVESTIGATION ON THE ELECTROCHEMISTRY OF RUTIN AND ITS ANALYTICAL APPLICATION

ABSTRACT An electrochemical investigation for rutin on glassy carbon electrode is presented. An adsorptive process is observed. The maximum coverage on the electrode surface is 5.09 × 10−10 mol/cm2, this area corresponding to a benzene ring with 3′,4′-dihydroxides adsorbed on the electrode surface; the other parts of rutin keep away from the surface. In the meantime, a new electrochemical method for determining rutin is presented. In a medium of 0.1 M acetate buffer solution (pH = 4.46), a very sensitive polargraphic adsorptive wave is observed by using a differential pulse voltammetry at about 0.29 V (vs. Ag/AgCl). The linear relationship between the peak current and the concentration of rutin exists in a range from 3.28 × 10−7 to 3.28 × 10−5 M. The detection limit of rutin is down to 2.51 × 10−8 M. This method has been applied to determine rutin in several samples of Chinese medicines. The results are satisfactory.

Spectrophotometric determination of palladium after solid-liquid extraction with 1-(2-pyridylazo)-2-naphthol at 90°C

Abstract An effective spectrophotometric determination of palladium with 1-(2-pyridylazo)-2-naphthol (PAN) using molten naphthalene as a diluent has been studied. A green complex of palladium with PAN is formed at 90°C. In the range of pH 1.5–7.5, the complex is quantitatively extracted into molten naphthalene. The organic phase is anhydrously dissolved in CHCl3 to be determined spectrophotometrically at 678 nm against the reagent blank. Beers law is obeyed over the concentration range of 0.5–10 ppm. The molar absorptivity and Sandells sensitivity are 1.2 × 104 l mol−1 cm−1 and 0.0070 mg cm−2, respectively. The optimum conditions for determination are obtained. The interferences of various ions are observed in detail. The method has been applied to the determination of palladium in synthetic samples.

Oxidative degradation of acridine orange induced by plasma with contact glow discharge electrolysis

Abstract Contact glow discharge electrolysis (CGDE) of acridine orange (AO) was investigated under different mediums, pH, and voltages. The results showed that 500 V was the optimum voltage for CGDE of AO under experimental conditions. The concentration and pH had no appreciable effect on the degradation of AO. Fe2+ had a remarkable catalytic effect on it. From the variation of AO concentration with the reaction time, it was demonstrated that the oxidation would be a first-order reaction. On the grounds of UV spectra of solution in the degradation process, we speculated the intermediate states. The rate constants and relevant coefficiencies were displayed under different conditions.

Kinetic determination of ascorbic acid by the BZ oscillating chemical system

A new analytical method for the determination of ascorbic acid by the perturbation caused by different amounts of ascorbic acid on the BZ oscillating chemical system involving the Ce(IV)-catalyzed reaction between potassium bromate and malonic acid in a acidic medium is proposed. The method relies on the linear relationship between the change in the oscillation amplitude of the chemical system and the concentration of ascorbic acid, which is in this work exposed for the first time. The calibration curve is linearly proportional to the concentration of ascorbic acid over the range 3.5x10(-6)-4.7x10(-4) M, with the regression coefficient is 0.9975. Two different methodologies were used to address the determination. Some aspects of the potential mechanism of action of ascorbic acid on the BZ oscillating chemical system are discussed in detail.

Kinetic-spectrophotometric determination of trace amounts of vanadium

A simple and sensitive kinetic-spectrophotometric method is described for the determination of vanadium and the possible mechanism of catalytic reaction is proposed. The method is based on the vanadium(V)-catalyzed oxidation of 1,8-diaminonaphthalene (DNA) by potassium bromate (Tiron as activator) at pH 3.8 and 40 degrees C. The reaction was monitored spectrophotometrically by measuring the increase in absorbance of oxidation products at 505 nm after a fixed time (6 min). The proposed method allowed the determination of vanadium in the range 0.025-15 ng ml(-1) with good precision and accuracy and the detection limit was down to 0.01 ng ml(-1). The method was found to be relatively selective and was applied successfully to the determination of vanadium in food and hair samples without previous separations. Recovery experiments have also been performed; excellent results were obtained.

Determination of trace europium based on new ternary fluorimetric enhancement system of europium(III) with thenoyltrifluoroacetone and trisalicylicamido triethylamine

In this work, a newly synthesized ligand, trisalicylicamido triethylamine, acts as a specific reagent for enhancing the fluorescence intensity of EuIII complex with thenoyltrifluoroacetone. The spectrofluorimetric determination of trace amounts of EuIII based on the above system was carried out and its luminescence mechanism was studied. The excitation and emission wavelengths are 348.9 nm and 613.4 nm, respectively. The fluorescence intensities vary linearly with the concentration of EuIII in the range 7.598 × 10–7 g l–1–3.799 × 10–4 g l–1 with a detection limit of 1.520 × 10–8 g l–1 and a standard deviation of 1.80 × 10–6 g l–1 for 10 measurements. The interferences of some rare-earth metals and inorganic ions are described. This method is a direct, rapid, selective and sensitive analytical procedure for the determination of trivalent europium in high purity yttrium oxide.

Determination of glutamic acid by an oscillating chemical reaction using the analyte pulse perturbation technique.

An analytical method for the determination of glutamic acid by the sequential perturbation caused by different amounts of glutamic acid on the oscillating chemical system involving the Cu(II)-catalyzed oscillating reaction between hydrogen peroxide and sodium thiocyanate in an alkaline medium is proposed. The method relies on the linear relationship between the changes in the oscillation amplitude of the chemical system and the concentration of glutamic acid. The reaction is implemented in a continuous-flow stirred-tank reactor, and changes in the oscillation amplitude on each perturbation are proportional to the glutamic acid concentration. The use of the analyte pulse perturbation (APP) technique permits sequential determinations on the same oscillating system owing to the expeditiousness with which the steady state is regained after each perturbation. The dynamic range lies between 2.5x10(-6) and 3.2x10(-4) M of glutamic acid, with the regression coefficient is 0.9987. The precision is excellent (less than 0.68% as relative standard deviation (R.S.D.)). Some aspects of the potential mechanism of action of glutamic acid on the oscillating system are discussed.