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  • Author or Editor: L. Gao x
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A novel multi-walled carbon nanotubes (MWCNTs) dispersive solid phase extraction (d-SPE) method which combined with gas chromatography (GC) coupled with electron capture detector (ECD) was developed for the determination of five pyrethroid pesticides in liquid milk for the first time. The effect of d-SPE conditions on the kinds of sorbent, MWCNTs and magnesium sulfate anhydro mass ratio, and extraction condition were researched, and then, the suitable method was found. Under the optimal conditions, the linear range was from 20 to 500 μg kg−1. The recoveries were from 81.8% to 112.1%, with the corresponding relative standard deviations (RSDs) less than 6%, correlation coefficients from 0.9978 to 0.9990, and limits of detection and quantification from 2.62 to 4.86 μg kg−1 and 8.73 to 16.2 μg kg−1. The proposed method is simple, fast, safe, and has high recovery and sensitivity applicable to analyze pyrethroid pesticides in liquid milk sample.

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Dauricine has a variety of pharmacological properties including anti-inflammatory, anti-arrhythmic, and antihypertensive effects as well as reversing multidrug resistance (MDR) of cancer cells. While its therapeutic application is increasing, its bioavailability of different administration routes has not been studied. In the present study, we developed and validated a liquid chromatography/electrospray ionization mass spectrometry method (LC-MS/MS). Using this method, we quantified dauricine in rat plasma after administration via intravenous (i.v.) injection, per oral (p.o.), and intraperitoneal injection (i.p.). Our results indicated that this method detected plasma dauricine with a good linearity in the range of 1.95–1000.00 ng/mL (r = 0.9997). The extraction method showed an average intra- and inter-day recovery of 98.21–104.35% and 98.0–103.58%, respectively. Dauricine showed a fast absorption and widespread distribution after administration in all three tested routes. After intravenous administration (2.5, 5.0, 10.0 mg/kg), the pharmacokinetics of dauricine exhibited a first-order kinetics. In addition, dauricine showed a slow elimination with a long half-life (t 1/2z) and double peaks phenomenon following p.o. and i.p. administration. Furthermore, using area under the plasma concentration-time curve (AUC), we calculated absolute bioavailability, which was over twofold higher when administered via i.p. than via p.o. administration. The newly obtained information from our study will provide important reference for dauricine dose and administration route in designing dauricine therapy for applicable diseases.

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We have developed a thermogravimetric system (TG system) for condensable gas adsorption by modifying a standard thermogravimetric analyzer Cahn TG 2121 and performed isotherm measurements of water vapor adsorption on Fuji Davison type RD silica gel and ethanol vapor adsorption on Maxsorp II activated carbon. For the water vapor-silica gel data, our results compare favorably with the data reported by the manufacturer and those obtained from a volumetric method. This confirms the reliability of our TG system for adsorbents which do not swell significantly. In addition, our isotherm data also provide useful design information for the development of adsorption chillers.

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A complex of neodymium perchloric acid coordinated with L-glutamic acid and imidazole, [Nd(Glu)(H2O)5(Im)3](ClO4)6·2H2O was synthesized and characterized by IR and elements analysis for the first time. The thermodynamic properties of the complex were studied with an automatic adiabatic calorimeter and differential scanning calorimetry (DSC). Glass transition and phase transition were discovered at 221.83 and 245.45 K, respectively. The glass transition was interpreted as a freezing-in phenomenon of the reorientational motion of ClO4 ions and the phase transition was attributed to the orientational order/disorder process of ClO4 ions. The heat capacities of the complex were measured with the automatic adiabatic calorimeter and the thermodynamic functions [H T-H 298.15] and [S T-S 298.15] were derived in the temperature range from 80 to 390 K with temperature interval of 5 K. Thermal decomposition behavior of the complex in nitrogen atmosphere was studied by thermogravimetric (TG) analysis and differential scanning calorimetry (DSC).

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The molar heat capacity C p,m of 1,2-cyclohexane dicarboxylic anhydride was measured in the temperature range from T=80 to 390 K with a small sample automated adiabatic calorimeter. The melting point T m, the molar enthalpy Δfus H m and the entropy Δfus S m of fusion for the compound were determined to be 303.80 K, 14.71 kJ mol−1 and 48.43 J K−1 mol−1, respectively. The thermodynamic functions [H T-H 273.15] and [S T-S 273.15] were derived in the temperature range from T=80 to 385 K with temperature interval of 5 K. The thermal stability of the compound was investigated by differential scanning calorimeter (DSC) and thermogravimetry (TG), when the process of the mass-loss was due to the evaporation, instead of its thermal decomposition.

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The curing kinetics of a bi-component system about o-cresol-formaldehyde epoxy resin (o-CFER) modified by liquid crystalline p-phenylene di[4-(2,3-epoxypropyl) benzoate] (p-PEPB), with 3-methyl-tetrahydrophthalic anhydride (MeTHPA) as a curing agent, were studied by non-isothermal differential scanning calorimetry (DSC) method. The relationship between apparent activation energy E a and the conversion α was obtained by the isoconversional method of Ozawa. The reaction molecular mechanism was proposed. The results show that the values of E a in the initial stage are higher than other time, and E a tend to decrease slightly with the reaction processing. There is a phase separation in the cure process with LC phase formation. These curing reactions can be described by the Šesták–Berggren (S–B) equation, the kinetic equation of cure reaction as follows:

\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $${\frac{{{\text{d}}\alpha }}{{{\text{d}}t}}} = A\exp \left( { - {\frac{{E_{\text{a}} }}{RT}}} \right)\alpha^{m} \left( {1 - a} \right)^{n}$$ \end{document}
.

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The thermogenic curves of the aerobic metabolism of the three strains of Bacillus thuringiensis B.t. A, B.t. B and B.t. C have been determined by using an LKB-2277 BioActivity Monitor. B.t. A was the host bacterium without foreign gene. B.t. B and B.t. C were constructed by transforming different foreign genes into the host B.t. A, respectively. B.t. B expressed erythromycin resistant gene, while B.t. C expressed both erythromycin resistant gene and tyrosinase gene. The heat flow rate of these strains is B.t. A> B.t. B >B.t. C. These results indicated that there is obvious interrelation between expression of foreign genes and heat flow rate of B.t. strains.

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Poly(AN—co—St) (PAS) and poly(AN—St—MMA)(PASM) were synthetized by emulsion polymerisation. The glass transition temperatures (T g) of the copolymers and the relationship between T g and the components of the copolymers were investigated by differential scanning calorimetry. The results show that T g for the AN—St bipolymers has apeak value in the range 115–118°C at a content of 50 mass% St. When methyl methacrylate was added, the T g of the terpolymer was decreased by about 2–6°C.The thermostability and the activation energy E of degradation were determined by thermogravimetric analysis.

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Carburization and coke deposition of unsupported and carbon-supported Fe, Mo and Fe−Mo catalysts in syngas have been studied using thermogravimetry. Compositions of the carbides formed are evaluated on the basis of the amount of metals in the catalysts and amount of carbon deposited during carburization. It is shown that carburization temperature and the nature of the carbides formed (Fe5C2 and Fe2C for iron and Mo2C for molybdenum) depend on the metals but are influenced by the support and metal loading. Coke deposition on these catalysts takes place as soon as carburization is complete.

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The catalytic performance of unsupported and carbon-supported Fe, Mo and Fe−Mo catalysts for Fischer-Tropsch synthesis is greatly influenced by the final reduction states of the catalysts. In this investigation, the reduction process of the catalysts by H2 was studied by using TG-DTG. The reduction process depends not only on the reducibility of metals but also on the nature of the support. Methanation of the support occurred as soon as the supported metals were completely reduced for the carbon-supported catalysts. For these, the reduction temperature should by carefully selected so that the metal oxides are reduced as completely as possible, whilst the methanation of the support must be avoided to obtain optimum reduced catalysts.

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