Monolithic octadecylsilyl-silica gel column for the high-speed ion chromatographic determination of acidity

A monolithic ODS-silica gel column modified by saturating it with lithium dodecylsulfate (Li-DS) was used to demonstrate the high-speed separation of H+ from other mono- and divalent cations, such as Na+, NH4+, K+, Mg2+ and Ca2+ using ion chromatography (IC). Using a 5 mM EDTA-2K solution containing 0.10 mM Li-DS (pH 4.80) as eluent, H+ was eluted with a sharp and symmetrical peak within 1.0 min before other cations at a flow-rate of 1.5 ml min(-1). The rapid elution of H+ and its conductimetric detection could be attributed to the presence of EDTA (HY2-), which can convert H+ ions as anions. i.e. H(+) + H2Y(2-) --> H3Y(-). The acidity of rainwater and deionized water samples was determined using this IC system with satisfactory results.     

A novel microwave dielectric ceramic Ca2Zn4Ti16O38: Preparation and dielectric properties

A novel microwave dielectric powder with composition of Ca₂Zn₄Ti₁₆O₃₈ was synthesized through a citrate sol-gel process. The development of crystalline phases with heat-treating temperature for the gel derived powders was evaluated by using thermo-gravimetric analysis and X-ray powder diffraction analysis techniques. The pure phase of Ca₂Zn₄Ti₁₆O₃₈ with crichtonite crystal structure was obtained at relatively low temperature of 1000 °C. The synthesized powder has high reactivity and the dense ceramics with single crystalline phase were obtained at low sintering temperature of 1100 °C. Impedance spectroscopy and microwave dielectric measurements on sintered samples showed the present compound to be a modest dielectric insulator with excellent dielectric properties of ε_r∼47-49, Qf value ∼27,800-31,600 GHz and τ_f∼+45 to +50 ppm/°C. It shows comparable microwave dielectric properties to other moderate-permittivity microwave dielectrics, but much lower sintering temperature of 1100 °C.     

茜素红与蛋白质分子Langmuir吸附聚集反应研究

在pH4.3的B-R缓冲体系中,用微相吸附-光谱修正技术[1]研究了茜素红(ARS)与牛血清白蛋白(BSA)、人血清白蛋白(HSA)的结合反应。其吸附结合常数分别为:KBSA-ARS=3.950×104,KHSA-ARS=4.377×104。染料与蛋白的最大结合数分别为NARS∶NBSA=9∶1,NARS∶NHSA=7∶1。经光谱修正技术计算结合产物的实际摩尔吸光系数分别为εBSA-ARS(537nm)=2.517×104L.mol-1.cm-1,εHSA-ARS(519nm)=2.051×104L.mol-1.cm-1,检出限BSA为19mg/L,HSA为23mg/L。经探讨该结合反应机理符合Langmuir吸附聚集反应方程。     

Determination of Procymidone, Pentachloroaniline and Methyl-pentachloro-phenylsulfide Residues in Wine by MSPD-GC-ECD

A rapid method based on matrix solid-phase dispersion (MSPD) was developed for the determination of procymidone, pentachloroaniline and methyl-pentachloro-phenylsulfide in wine. After the optimisation of different parameters such as the type of adsorbent, the extraction solvent, and the extraction assistance by sonication. The analysis of samples was accomplished using gas chromatography with electron-capture detector (GC-ECD). Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. The recovery of the method was in the range 82.4–93.7% and a good linear relationship (R ² ≥ 0.9992) with relative standard deviations lower than 8%. The limits of detection (LOD) ranged from 0.1 to 0.4 μg L^?1. The proposed method was applied to the analysis of these compounds in commercial wine samples.     

Simultaneous HPLC Determination of Four Key Metabolites in the Metabolic Pathway for Production of 1,3-Propanediol from Glycerol

A high-performance liquid chromatographic (HPLC) method with refractive-index detection has been developed for simultaneous analysis of glycerol, dihydroxyacetone (DHA), 3-hydroxypropionaldehyde (3-HPA), and 1,3-propanediol (1,3-PD), four key substances in the metabolic pathway for production of 1,3-PD from glycerol by microorganism fermentation. The compounds were separated on a 300 mm × 7.8 mm ion-exclusion column with a 65:35 (v/v) mixture of deionized water and acetonitrile, containing 0.0005 M H₂SO₄, as mobile phase. The flow rate was 0.5 mL min^?1. Under these conditions the retention times of 3-HPA, DHA, glycerol, and 1,3-PD were 6.87, 14.63, 16.37, and 18.50 min, respectively. Relative standard deviations and average recoveries were between 0.42 and 0.63% and between 96.7 and 103.1%, respectively; detection limits were between 0.017 and 0.038 g L^?1. The method enabled separation of these compounds.     

Hydroxylamine derivative in the Purex Process

N,Ndiethylhydroxylamine (DEHAN) can rapidly reduce Pu(IV) and Np(VI) extractable with trinbutyl phosphate (TBP) to Pu(III) and Np(V) unextractable with TBP in nitric acid solution. In order to apply DEHAN in the purification cycle step of U (noted as contactor 2D) of the secondcycle of the Purex Process to separate Np and Pu from U, the reduction of Np(VI) and the stability of Np(V) with DEHAN and the singlestage reduction extraction and backextraction of Np(VI) have been studied according to the experimental conditions of contactor 2D. The results show that more than 99% of Np(VI) can entirely be reduced to Np(V) with DEHAN within a few minutes either in aqueous or in organic phase containing uranium and without containing uranium, and more than 99% of Np(VI) can be backextracted from the organic to the aqueous phase with DEHAN as a reductant. More than 99% of Np(V) exists in nitric acid solution at least for 8 hours in presence of 0.01 mol/l DEHAN. These results are of benefit to the cascade extractionseparation of U/Np in contactor 2D in order to decontaminate Np from U.     

Rapid determination of volatile constituents of Michelia alba flowers by gas chromatography-mass spectrometry with solid-phase microextraction

The volatile constituents of Michelia alba flowers, including fresh flowers, frozen flowers and withered flowers, were investigated by GC-MS. The volatiles in a simulated natural environment were sampled by solid-phase microextraction (SPME), with a 100 microm polydimethylsiloxane fiber at 25+/-5 degrees C for 4 h. The fibers were desorbed in a GC injection liner at 250 degrees C for 3 min. With headspace SPME-GC-MS analysis, 61 peaks were separated. The main compounds in headspace of fresh Michelia alba flowers included alpha-myrcene, (S)-limonene, (R)-fenchone, linalool, camphor, caryophyllene, germacrene D, etc., a greater number of compounds than for frozen flowers and withered flowers. At the same time, the biomarkers of fresh flowers were compared with the frozen flowers and withered flowers. In this study, headspace SPME-GC-MS afforded a simple and more sensitive sampling method for fresh Michelia alba flowers and other fresh flowers.     

Determination of monovalent inorganic anions in high-ionic-strength samples by electrostatic ion chromatography with suppressed conductometric detection

A new ion chromatographic (IC) system has been established by using micelles of 3-(N,N-dimethylmyristylammonio)propanesulfonate (Zwittergent 3-14) loaded onto a reversed-phase packed column as the separation column with an electronic rotary switching valve packed-bed suppressor for conductometric detection of inorganic anions. An aqueous H3BO3-Na2B4O7 solution has been demonstrated to be the most desirable eluent for this IC system. The relationship between retention time and the concentration of the borate eluent was determined for a series of model anionic analytes and this relationship was found to be opposite to that exhibited in a conventional anion-exchange IC system. The rapid elution and complete separation of monovalent inorganic anions were obtained by initially using a high-concentration borate solution as the eluent for a short-period, and then switching to a lower-concentration borate eluent to complete the separation. Detection limits for nitrite, bromide, nitrate, and chlorate were 0.85, 0.88, 0.95 and 4.8 microM, respectively, when a 7.0 mM Na2B4O7 eluent was used. Moreover, the ability to directly detect these monovalent anions in samples containing high concentrations of sulfate and/or chloride ions provided a major advantage of this approach.     

Synthesis of new 1,3-bis（phenylethynyl）disilazanes

Three new 1,3-bis(phenylethynyl)disilazanes were synthesized from the reaction of 1,3-dichlorodisilazanes with (phenylethy- nyl)lithium,and characterized by infrared (IR) spectra,nuclear magnetic resonance (NMR) and mass spectrometry (MS).     

Electrophoresis of concentrated mercury drops

The electrophoretic behavior of concentrated monodispersed, positively charged mercury drops is investigated theoretically. The present study extends previous analyses by considering arbitrary surface potentials, double-layer polarization, and the interaction between adjacent double layers. The coupled equations describing the spatial variations in the flow field, the electric field, and the concentration field are solved by a pseudo-spectral method. For a low surface potential phi(r), the mobility increases monotonically with kappaalpha; kappa and alpha are respectively the reciprocal Debye length and the radius of a mercury drop. For medium and high phi(r), the mobility curve has a reflection point, which arises from the interaction of adjacent double layers, for kappaalpha. Also, if phi(r) is high, the mobility curve may exhibit a local minimum as kappaalpha varies. This phenomenon is pronounced if the concentration of the dispersed phase is high. If the double layer is thick, the mobility increases with phi(r), and the reverse is true if it is thin. We show that the higher the concentration of the dispersed phase the smaller the mobility, and as kappaalpha becomes large the mobility approaches a constant value, which is independent of the concentration of the dispersed phase. The mobility of mercury drops is larger than that of the corresponding rigid particles.