Jingguo Hou

Inorganic/organic mesoporous silica as a novel fiber coating of solid-phase microextraction

Mesoporous materials were employed as fast, sensitive and efficient fiber coatings of solid-phase microextraction (SPME) for the first time. Three micrometer as-synthesized C(16)-MCM-41 particles were immobilized onto stainless steel wire with 100mum coating thickness. In combination with high performance liquid chromatography (HPLC), extraction efficiency and selectivity of C(16)-MCM-41 were investigated using aromatic hydrocarbons. Effect of extraction and desorption time, extraction temperature, stirring rate and ionic strength on extraction efficiency were examined. Aanalytical merits of SPME with C(16)-MCM-41 coating were evaluated. The chromatographic peak area is proportional to the concentration of anthracene in the range 0.5-150mugl(-1). The limit of detection was 0.05mugl(-1) (S/N=3) and the relative standard deviation (R.S.D.) was 0.033%.

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.

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.

Simultaneous determination of inorganic anions and cations by ion chromatography with indirect photometric detection

Inorganic cations and anions were separated simultaneously on a silica-based Shim-pack WAX-1 column. The method is shown to provide efficient separation of Ca2+, Mg2+, Cl− and NO3−. Using 1 mM phthalate—6 mM EDTA at pH 6.57 as the eluent, a mixture containing these ions was separated in less than 6 min with detection limits of 1.2–2 ng. The effects of the eluent pH, concentration and composition on the retention behaviour of the analytes were studied. Two practical applications are described.

Enantiomeric Separation Using Erythromycin as a New Capillary Zone Electrophoresis Chiral Selector

Abstract The chiral selectivity of erythromycin was examined in capillary zone electrophoresis using a fused silica capillary column. Excellent chiral separations of four derivatives of biphenyldimethylester for antihepatitis drugs (A1–A4) have been achieved, respectively. The effects of various experimental factors such as chiral selector concentration and pH value, voltage and temperature, organic modifiers on enantiomeric resolution were investigated. Enatioresolution was found to significantly improve with increasing chiral selector concentration while the migration time of the analytes showed slight increase. Enantioselectivities of the chiral solutes were considerable influenced by the content of organic modifieres in running buffer. For chiral separation of the above racemates, the optimal run-buffer consisting of 20 mM erythromycin, 50 mM phosphate and 50% methanol (pH = 6) was obtained by experiment.

Construction and evaluation of a novel In(III) liquid ion-selective membrane electrode

A liquid ion-selective membrane electrode containing a chloroform-acetonitrile (10:1) solution of the complex of In(III) with 1-benzyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and diphenylguanidine is described. The basic electrode performance characteristics were evaluated according to IUPAC recommendations. The slope of the calibration graph (electrode potential v. concentration) was 18.7 mV (pIn)(-1) in the pIn range 4.5-1 (pH 6). Direct potentiometric determination of In(III) showed an average recovery of 99.1% with a standard deviation of 1.2%. The method is recommended for the precise direct potentiometric assay of In(III) in metals and minerals without a prior separation.

Solid-Liquid Extraction, Separation, and Determination of Rare Earths With Di-(2-Ethylhexyl)Phosphoric Acid

Abstract The extraction behavior of rare earths has been studied with di-(2-ethylhexyl)phosphoric acid (DEHP) in paraffin, naphthalene, and biphenyl. The group separation of rare earths with DEHP was further examined in paraffin. In the presence of 0.3 mol/L HNO3 and 2.0 mol/L DEHP, light rare earths can be separated from heavy ones in rare earth ores. Quantitative analysis of the rare earths was then done by spectrophotometry.