Retention modeling and optimization of pH value and solvent composition in HPLC using back-propagation neural networks and uniform design

A novel method for the optimization of pH value and composition of mobile phase in HPLC using artificial neural networks and uniform design is proposed. As the first step. seven initial experiments were arranged and run according to uniform design. Then the retention behavior of the solutes is modeled using back-propagation neural networks. A trial method is used to ensure the predicting capability of neural networks. Finally, the optimal separation conditions can be found according to a global resolution function. The effectiveness of this method is validated by optimization of separation conditions for both basic and acidic samples.

Photo-sensitized oxidation in natural water via .OH radicals

A method is presented for determining production and consumption rates of .OH radicals produced photochemically in natural surface waters. It is based on the determination of the kinetics by which the concentration of a specified trace compound decreases during irradiation. In samples from Lake Greifensee (Switzerland) low production rates for .OH limit its possible effects. In addition, fast consumptions by the natural dissolved organic solutes and by the bicarbonate protect organic micropollutants from oxidation by .OH. Neither direct nor indirect H2O2 photolysis was a significant source of .OH in the lakewater studied lacking iron, whereas nitrate photolysis could have been a source. Comparison with reaction kinetic formulations allows generalizations for other types of waters.

An Efficient Ullmann-Type C-O Bond Formation Catalyzed by an Air-Stable Copper(I)-Bipyridyl Complex

An efficient O-arylation of phenols and aliphatic alcohols with aryl halides was developed that uses an air-stable copper(I) complex as the catalyst. This arylation reaction can be performed in good yield in the absence of Cs2CO3. A variety of functional groups are compatible with these reaction conditions with low catalyst loading levels.

Successful establishment of MEKC with electrochemiluminescence detection based on one functionalized ionic liquid

Herein, one water-soluble functionalized ionic liquid, 1-butyl-3-methylimidazolium dodecyl sulfate ([BMIm(+)][C12H25SO4-]), was designed and its superiorities either used as supporting electrolytes or as additives for successful establishment of MEKC with electrochemiluminescence (ECL) detection (MEKC-ECL) method were investigated. Compared with the common supporting electrolytes such as phosphate solution, 1-butyl-3-methylimidazolium dodecyl sulfate solution used as running buffers led to greatly enhanced ECL intensities and column efficiencies for negative targets, a little increase for neutral-charge ones while maintained nearly unchanged for positive ones due to the electrostatic forces between the large cation BMIm(+) and the solutes and the hydrophobic interactions resulting from the large anion C12H25SO4.

Orientation of Syndiotactic Polystyrene Crystallized in Cylindrical Nanopores

Syndiotactic polystyrene (sPS) nanorods with different diameters have been prepared by using anodic aluminum oxide templates, and the orientation of the sPS crystals in the nanorods has been investigated by FT-IR spectroscopy. It is found that the c axis of the beta' crystals preferentially oriented perpendicular to the axis of the nanorod, and the degree of orientation is lower as the diameter of the nanorod decreases. This unexpected result is attributed to nuclei formed at the surface of the nanopores and their subsequent growth, in addition to the preferential growth compatible with the pore direction by the nuclei formed in the bulk film and in the nanorods.

Studies on the content variation of chemical constituents during the combination of ginseng with veratrum nigrum by ESI-MS and HPLC-ESI-MS

To study the content variation of ginsenosides and alkaloids during combination of ginseng with veratrum nigrum, the ginsenosides and alkaloids in the decoction of ginseng with veratrum nigrum were analyzed and compared by high performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) and electrospray ionization-mass spectrometry (ESI-MS). In the compatible decoction, eight ginsenosides and eight alkaloids. were detected, and the contents of six ginsenosides were found to be reduced, on the contrary, the contents of six alkaloids were increased. During combination of ginseng with veratrum nigrum, the contents of ginsenosides were reduced and those of the toxic alkaloids were increased. From the chemical point of view, the traditional theory is right that ginseng and veratrum nigrum are incompatible with each other.

Study on the variation of chemical constituents during combination of ginseng with trogopteroum feces and semen raphani by high performance liquid chromatography-mass spectrometry

A high performance liquid chroatography-electrospray ionization-mass spectrometric method was developed for analysis and identification of ginsenosides from the decoction of ginseng, ginseng with trogopteroum feces and ginseng with semen raphani. Ten ginsenosides were separated and detected. The content variation of these ginsenosides was researched. The experimental results showed, that ginsenosides were less in compatible decoction than in separate one expect Ro. the stripping of ginsenosides were restrained by semen raphani and during combination of ginseng with trogopteroum feces, the precipitates were produced by ginsenosides.

Biodegradable poly(L-lactide)/poly(epsilon-caprolactone)-modified montmorillonite nanocomposites: Preparation and characterization

New nanocomposites were prepared by melt blending poly(L-lactide) (PLLA), poly(epsilon-caprolactone) (PCL), and organically modified montmorillonite (OMMT). The obtained nanocomposites showed enhanced tensile strength, modulus and elongation at break than that of PLLA/PCL blends. The dynamic mechanical analysis showed the increasing mechanical properties with temperature dependence of nanocomposites. Wide-angle X-ray diffraction analysis and transmission electron microscopy indicated that the material formed the nanostructure. Adding OMMT improved the thermal stability and crystalline abilities of nanocomposites. The morphology was investigated by environmental scanning electron microscopy, which showed that increasing content of OMMT reduces the domain size of phase-separated particles. The specific interaction between each polymer and OMMT was characterized by the Flory-Huggins interaction parameter, B, which was determined by the equilibrium melting point depression of nanocomposites. The final values of B showed that PLLA was more compatible with OMMT than PCL.

Synthesis and characterization of photo-cross-linked hydrogels based on biodegradable polyphosphoesters and poly(ethylene glycol) copolymers

Novel biodegradable hydrogels by photo-cross-linking macromers based on polyphosphoesters and poly(ethylene glycol) (PEG) are reported. Photo-cross-linkable macromers were synthesized by ring-opening polymerization of the cyclic phosphoester monomer 2-(2-oxo-1,3,2-dioxaphospholoyloxy) ethyl methacrylate (OPEMA) using PEG as the initiator and stannous octoate as the catalyst. The macrorners were characterized by H-1 NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography measurements. The content of polyphosphoester in the macromer was controlled by varying the feed ratio of OPEMA to PEG. Hydrogels were fabricated by exposing aqueous solutions of macromers with 0.05% (w/w) photoinitiator to UV light irradiation, and their swelling kinetics as well as degradation behaviors were evaluated. The results demonstrated that cross-linking density and pH values strongly affected the degradation rates. The macromers was compatible to osteoblast cells, not exhibiting significant cytotoxicity up to 0.5 mg/mL. "Live/dead" cell staining assay also demonstrated that a large majority of the osteoblast cells remained viable after encapsulation into the hydrogel constructs, showing their potential as tissue engineering scaffolds.

Phase separation of PS/PVME blend films induced by capillary force

The phase behavior of a miscible PS/PVME (80/20, w/w) blend film in a confined geometry has been investigated at the annealing temperature much lower than the low critical solution temperature (LCST) of the blend. When the annealing temperature (52degreesC) is near the glass transition temperature of the blend (51.2degreesC), PVME-rich phase at the air-film surface under a microchannel forms smaller protrusion. When the annealing temperature is increased to 70degreesC, the protruding stripes, which are almost developed, are mainly composed of the mobile PVME-rich phase. These results reveal that the capillary force lead to the enrichment of PVME-rich phase at the air-polymer interface of a PDMS microchannel, that is, the capillary force lithography (CFL) can induce the phase separation of PS/PVME blend films.

Determination of degree of crystallinity of Nylon 1212 by wide-angle X-ray diffraction

Based on the X-ray scattering intensity theory and using the approximate expression for the atomic scattering factor, the correction factors for three crystalline peaks and an amorphous peak of Nylon 1212 were calculated and the formula of degree of crystallinity of Nylon 1212 was derived by a graphic multipeak resolution method. The degree of crystallinity calculated from the WARD method is compatible with those obtained by density and calorimetry methods.

The preparation of phenolic resin/montmorillonite nanocomposites by suspension condensation polymerization and their morphology

Phenolic resin/clay nanocomposites were prepared using a suspension condensation polymerization method that was suitable to both novolac and resole. Natural montmorillonite and two kinds of organic modified montmorillonite were adopted to investigate the effect of modification on the final morphology of the nanocomposites. X-ray diffraction (XRD) measurements and Transmission Electron Microscope (TEM) observations showed that clay platelets were easier to be exfoliated or intercalated in novolac than in resole because novolac usually has a linear structure. The modifier with a phenyl ring was more compatible with novolac (or resole) than the aliphatic type modifier. The influence of curing on the morphology was studied as well. An exfoliation-adsorption and in situ condensation mechanism was proposed on the formation of the nanocomposites.

Progress in amperometric detection for capillary electrophoresis

As a high efficiency separation technique, capillary electrophoresis(CE) has been widely used in various fields of analytical science. Amperometry is one of the most sensitive electrochemical detection methods in CE. The capillary/electrode decoupling mechanism, applications,of new electrode systems in CE, detection cell technique are discussed in detail. Amperometric detection is compatible with microfabricated CE chips and will make the concept of lab-on-a-chip become a reality. Because of these progresses, amperometry is becoming a widely acceptable detection method,for more chemical and biological analytes.

Mechanical properties of poly(beta-hydroxybutyrate)/poly(ethylene oxide) blends

Tensile properties of poly (P-hydroxybutyrate)/poly (ethylene oxide) (PHB/PEO) blends were reported in this paper. It was found that the blends of PHB with different molecular-weight PEO exhibited different mechanical properties. The mechanical properties of the blends of PHB and PEO3 (M-w=0.3x10(6)) were very poor. However, the blends of PHB and PEO5 (M-w=5x10(6)) showed compatible in mechanical properties. Excellent synergism was observed not only in tensile stress and tensile elongation but also in modulus. Moreover, the ductility of the blends could be improved further under proper heat-treatment.

Compatibilizing effect of polystyrene-block-poly(4-vinylpyridine) for poly(2,6-dimethyl-1,4-phenyleneoxide) chlorinated polyethylene blends

The compatibilizing effect and mechanism of compatibilization of the diblock copolymer polystyrene-block-poly(4-vinylpyridine) P(S-b-4VPy) on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/chlorinated polyethylene (CPE) were studied by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical properties and FTIR measurements. The block copolymer was synthesized by sequential anionic polymerization and melt-blended with PPO and CPE. The results show that the P(S-b-4VPy) added acts as an effective compatibilizer, located at the interface between the PPO and the CPE phase, reducing the interfacial tension, and improving the interfacial adhesion. The tensile strength and modulus of all blends increase with P(S-b-4VPy) content, whereas the elongation at break increases for PPO-rich blends, but decreases for CPE-rich blends. The polystyrene block of the diblock copolymer is compatible with PPO, and the poly(4-vinylpyridine) block and CPE are partially miscible.