Jinzhang Gao

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 phenol in aqueous electrolyte induced by plasma from a direct glow discharge

The liquid-phase oxidation of phenol induced by plasma that was generated from direct glow discharges at the tip of a platinum anode in aqueous electrolyte was investigated. Various influencing factors such as the initial pH, the concentration of reactants and the catalytic action of Fe2+ were examined. The results suggest that the reaction is a pseudo-first-order kinetic reaction; the initial pH significantly affects the degradation velocity and ferrous ions displayed a remarkable catalytic effect on the oxidation. The major oxidation intermediates were identified with high-performance liquid chromatograph and ion chromatograph analysis. It was found that the degradation proceeded differently in the presence and absence of catalysts and consequently two degradation pathways were proposed.

Highly sensitive and selective dopamine biosensor based on 3,4,9,10-perylene tetracarboxylic acid functionalized graphene sheets/multi-wall carbon nanotubes/ionic liquid composite film modified electrode.

A sensitive and selective electrochemical sensor for determination of dopamine (DA) was fabricated based on 3,4,9,10-perylene tetracarboxylic acid functionalized graphene sheets, multi-wall carbon nanotubes and ionic liquid modified glass carbon electrode and the properties of modified electrode were characterized by scanning electron microscopy, transmission electron microscope and electrochemical impedance spectroscopy. The modified electrode showed excellent electrocatalytic activity toward the oxidation of DA. Meanwhile, a possible reaction mechanism related to the oxidation of DA was proposed. The differential pulse voltammetry was used for the determination of DA in the presence of 500 μM ascorbic acid and 330 μM uric acid under the optimum conditions and a good linear relationship between peak current and the concentration of DA was obtained in the concentration range from 0.03 μM to 3.82 mM with a detection limit of 1.2×10(-9) M (S/N=3). Moreover, the proposed method was successfully applied to determine DA in real sample and satisfactory results were obtained. The results showed that the modified electrode exhibits an excellent catalytic activity, good sensitivity, reproducibility and long-term stability.

A novel and simple strategy for simultaneous determination of dopamine, uric acid and ascorbic acid based on the stacked graphene platelet nanofibers/ionic liquids/chitosan modified electrode.

A promising electrochemical sensor for simultaneous determination of dopamine (DA), uric acid (UA) and ascorbic acid (AA) was fabricated based on the stacked graphene platelet nanofibers (SGNF)/ionic liquid (IL)/chitosan (CS) modified electrode. The SGNF/IL/CS modified electrode possessed excellent electrocatalytic activity towards the oxidation of DA, UA and AA with obvious reduction of over-potential and increased peak current, and the separations of oxidation peak potentials of DA-UA, DA-AA, and UA-AA were of 151, 213 and 364 mV, respectively. Under the optimum conditions, the linear range for the detection of DA, UA and AA were 0.05-240, 0.12-260, and 30-350 μM with the lowest detection limits of 0.05, 0.10 and 14.8 μM for DA, UA and AA, respectively. In addition, the electrochemical sensor showed high sensitivity, excellent selectivity, reproducibility and long-term stability.

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 determination of hydroquinone by a Belousov–Zhabotinskii oscillating chemical reaction

Abstract A novel and convenient method with good selectivity and high sensitivity for the determination of hydroquinone (HQ) based on the Belousov–Zhabotinskii (B–Z) oscillating chemical reaction has been presented. The optimum condition for the determination has also been investigated. In the B–Z reaction system, when the sample was injected, the change of the amplitude is linearly proportional to the logarithm of the concentration of HQ in the range 1.0×10 −2 –2.0×10 −4 M ( r =0.9965), whereas, when the concentration of HQ is over the range from 2.5×10 −4 to 4.0×10 −7 M, the calibration curve fits a second-order polynomial equation very well ( r =0.9983).