Investigation of sol-gel transition in Pluronic F127/D2O solutions using a combination of small-angle neutron scattering and Monte Carlo simulation

Physical gelation in the concentrated Pluronic F127/D2O solution has been studied by a combination of small-angle neutron scattering (SANS) and Monte Carlo simulation. A 15% F127/D2O solution exhibits a sol-gel transition at low temperature and a gel-sol transition at the higher temperature, as evidenced by SANS and Monte Carlo simulation studies. Our SANS and simulation results also suggest that the sol-gel transition is dominated by the formation of a percolated polymer network, while the gel-sol transition is determined by the loss of bound solvent. Furthermore, different diffusion behaviors of different bound solvents and free solvent are observed. We expect that this approach can be further extended to study phase behaviors of other systems with similar sol-gel phase diagrams.

The use of CE-electrochemiluminescence with ionic liquid for the determination of bioactive constituents in Chinese traditional medicine

CE/tris(2,2-bipyridyl) ruthenium(ll) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL), CEECL, with an ionic liquid (IL) detection system was established for the determination of bioactive constituents in Chinese traditional medicine opium poppy which contain large amounts of coexistent substances. A minimal sample pretreatment which involves a one-step extraction approach avoids both sample loss and environmental pollution. As the nearby hydroxyl groups in some alkaloid such as morphine may react with borate to form complexes and IL, as a high-conductivity additive in running buffer, could cause an enhanced field-amplified effect of electrokinetic injection. Running buffer containing 25 mM borax-8 mM 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)) IL (pH 9.18) was used which resulted in significant changes in separation selectivity and obvious enhancement in ECL intensities for those alkaloids with similar structures. Sensitive detection could be achieved when the distance between the Pt working electrode and the outlet of separation capillary was set at 150 mu m and the stainless steel cannula was fixed approximately 1 cm away from the outlet of the capillary. Quantitative analysis of four alkaloids was achieved at a detection voltage of 1.2 V and a separation voltage of 15 kV in less than 7 min.

Facile separation and determination of Aconitine alkaloids in traditional Chinese medicines by CE with tris(2,2 '-bipyridyl) ruthenium(II)-based electrochemi-luminescence detection

A facile CE method coupled with tris(2,2'-bipyridyl) ruthenium(ll)-based electrochem iluminescence [Ru(bpy)(3)(2+)] detection was developed for simultaneous determination of Aconitum alkaloids, i.e., hypaconitine (HA), aconitine (AC), and mesaconitine (MA) in baseline separation. The optimal separation of these Aconitum alkaloids was achieved in a fused-silica capillary column (50 cm x 25 mu m id) with 30 mM phosphate solution (pH 8.40) as running buffer at 12 kV applied voltage. The three alkaloids can be determined within 10 min by a single run. The calibration curves showed a linear range from 2.0 x 10(-7) to 2.0 x 10(-5) M for HA, 3.4 x 10(-7) to 1.7 x 10(-5) M for AC, and 3.8 x 10(-7) to 1.9 x 10(-5) M for MA. The RSDs; for all analytes were below 3.01%. Good linear relationships were found with correlation coefficients for all analytes exceeding 0.993. The detection limits were 2.0 x 10(-8) M for HA, 1.7 x 10(-7) M for AC, and 1.9 x 10(-7) M for MA under optimal conditions. This method was successfully applied to determine the three alkaloids in Aconitum plants.

CE coupling with end-column electrochemiluminescence detection for chiral separation of disopyramide

CE with electrochemiluminescence, (ECL) detection technique was successfully applied for the chiral separation of a kind of class IA antiarrhythmic racemic drug. To the best of our knowledge, this is the first report of ECL detection used in chiral CE. To get better detection sensitivity and good enantioresolution at the same time, the conditions of capillary inlet and outlet buffer were systematically optimized. Unlike the traditional chiral separation method, the buffers we used in the capillary inlet and outlet differed from each other in terms of buffer pH, ionic strength, type of BGE as well as buffer composition. Under the optimum conditions, baseline enantioseparation and highly sensitive detection of the enantiomers were achieved. Wide linear relationship of each enantiomer was achieved in the range of 5 x 10(-7) to 2 x 10(-5) mol/L with relative coefficients of 0.996 and 0.997, respectively. The detection limits were estimated to be 8 x 10(-8) and 1.0 X 10(-7) mol/L (S/N = 3) for the enantiomers, respectively. In addition, a successful application of this new method to the chiral separation of the racemic drug in spiked plasma samples confirmed the validity and applicability of the chiral CE-ECL method.

Electrogenerated chemiluminescence sensing platform using Ru(bpy)(3)(2+) doped silica nanoparticles and carbon nanotubes

An effective electrogenerated chemiluminescence (ECL) sensor was developed by coimmobilization of the Ru(bpy)(2)(3+)-doped silica (RuDS) nanoparticles and carbon nanotubes (CNTs) on glassy carbon electrode through hydrophobic interaction. The uniform RuDS nanoparticles were prepared by a water-in-oil (W/O) microemulsion method and Ru(bpy)(3)(2+) doped inside could still maintain its high ECL efficiency. With such unique immobilization method, a great deal of Ru(bpy)(3)(2+) was immobilized three-dimensionally on the electrode , which could greatly enhance the ECL response and result in the increased sensitivity. On the other hand, CNTs played dual roles as matrix to immobilize RuDS nanoparticles and promoter to accelerate the electron transfer between Ru(bpy)(3)(2+) and the electrode. The as-prepared ECL sensor displayed good sensitivity and stability.

Determination of total calcium in plasma by flow injection analysis with tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescent detection

We described here a new method for the determination of total calcium in plasma. The method is based on the precipitation of calcium with excess oxalate and the measurement of residual oxalate by flow injection analysis with Ru(bpy)(3)(2+) electrochemiluminescent detection. It has the advantages of extremely stable reagent, user-friendly instrument, high selectivity, good analytical recovery, wide dynamic range, and nice correlation with atomic absorption spectroscopy. The calibration plot for calcium is linear over a concentration range from 0.5 mmol L-1 to 4.8 mmol L-1, which is wider than those obtained by most other methods. The analytical recoveries for plasma calcium are 98.4-101.2% with coefficients of variation (CVs) of 1.96-2.52%. The within-day CVs range from 0.76% to 0.95%, and between-day CVs were from 1.12% to 1.46%. The time for each injection is one minute. Because the proposed method can be readily carried out on increasingly popular instruments for Ru(bpy)(3)(2+) ECL immunoassays and DNA probe assays, Ru(bpy)32+ ECL method is suitable for routine clinical analysis of calcium.

Different colloids self-assembly in micromolding

Micromolding in capillaries (MIMIC) and non-conformal contact micromolding (NCCM) were employed to pattern the silica microspheres by the use of capillary forces. Three types of silica microspheres aggregations, small dot, ring and grid patterns, from the same prepatterned poly(dimethylsiloxane) (PDMS) stamps, were created by tuning the contact mode between the PDMS mold and the substrate and the concentration of silica microspheres suspension during the micromolding. The formation mechanisms of different patterns were discussed.

Complex aggregates of spherical colloids via modified micromolding in capillaries

This paper describes a simple approach to fabricate aggregates composed of monodispersed silica microspheres by modified micromolding in capillaries (MIMIC). Two different kinds of contact modes, namely, conformal contact and non-conformal contact, between the poly(dimethylsiloxane) (PDMS) mold and the underlying prepatterned substrate, can be controlled during the micromolding, which result in the formation of different aggregates under the influence of template confinement and capillary forces. These aggregates, including woodpile structure, discoid, conoid and rectangular clusters, possess well-controlled sizes and orientation. The possible mechanisms for the formation of different aggregates are discussed in detail.

Complex aggregates of silica microspheres by the use of a polymer template

Evaporation of a droplet of silica microsphere suspension on a polystyrene and poly(methyl methacrylate) blend film with isolated holes in its surface has been exploited as a means of particles self-assembly. During the retraction of the contact line of the droplet, spontaneous dewetting combined with the strong capillary force pack the silica microspheres into the holes in the polymer surface. Complex aggregates of colloids are formed after being exposed to acetone vapor. The morphology evolution of the underlying polymer film by exposure to acetone solvent vapor is responsible for the complex aggregates of colloids formation.

Melt rheological properties of polypropylene-polyarnide6 blends compatibilized with maleic anhydride-grafted polypropylene

The melt rheological properties of binary uncompatibilized polypropylene -polyamide6 (PP-PA6) blends and ternary blends compatibilized with maleic anhydride-grafted PP (PP-PP-g-MAH-PA6) were studied using a capillary rheometer. The experimental shear viscosities of blends were compared with those calculated from Utracki's relation. The deviation value delta between these two series of data was obtained. In binary PP-PA6 blends, when the compatibility between PP and PA6 was poor, the deformation recovery of dispersed PA6 particles played the dominant role during the capillary flow, the experimental values were smaller than those calculated, and delta was negative. The higher the dispersed phase content, the more deformed the droplets were and the lower the apparent shear viscosity. Also, the absolute value of delta increased with the dispersed phase composition. In ternary PP-PP-g-MAH-PA6 systems, when the compatibility between PP and PA6 was enhanced by PP-g-MAH, the elongation and break-up of the dispersed particles played the dominant role, and the experimental values were higher than calculated. It was observed that the higher the dispersion of the PA6 phase, the higher the delta values of the ternary blends and the larger the positive deviation.

Morphology and melt rheology of nylon 11/clay nanocomposites

Nylon 11 (PA11)/clay nanocomposites have been prepared by melt-blending, followed by melt-extrusion through a capillary. Transmission electron n-Licroscopy shows that the exfoliated clay morphology is dominant for low nanofiller content, while the intercalated one is prevailing for high filler loading. Melt rheological properties of PA11 nanocomposites have been studied in both linear and nonlinear viscoelastic response regions. In the linear regime, the nanocomposites exhibit much higher storage modulus (G') and loss modulus (G") values than neat PAIL The values of G' and G" increase steadily with clay loading at low concentrations, while the G' and G" for the sample with 5 wt % clay show an inverse dependence and lie between the modulus values of the samples with 1 and 2 wt % of clay. This is attributed to the alignment/orientation of nanoclay platelets in the intercalated nanocomposite induced by capillary extrusion. In the nonlinear regime, the nanocomposites show increased shear viscosities when compared with the neat resin. The dependence of the shear viscosity on clay loading has analogous trend to that of G' and G".

毛细管电泳安培检测法在中草药分析中的应用

Capillary electrophoresis (CE) with amperometric detection (AD) has been widely used in various fields of analytical science, especially in the pharmaceutical industry recently due to its high separation efficiency and low detection limit. The determination of active ingredients in Chinese herb medicines by CE-AD is of great importance in developing the researches on pharmacology of herbs, quantitative analysis and quality control. Analyses of the effective components in Chinese herb medicines and compound Chinese herb medicine by CE-AD are reviewed in this paper. In contrast with other analysis methods, the advantage of CE-AD is discussed. The development in analyses of traditional Chinese medicine (TCM) by CE-AD in future is mentioned.

Evaluation of bioeffects of a long-term administering ChangLe on rat by proton NMR method and biochemical examination

High resolution H-1 nuclear magnetic resonance ( NMR) spectroscopy has been employed to assess long-term toxicological effects of ChangLe (a kind of rare earth complex applied in agriculture). Male Wistar rats were administrated orally with ChangLe at doses of 0, 0.1, 0.2, 2.0, 10 and 20 mg/kg body weight daily, respectively, for 6 months. Urine was collected at-day 30, 60, go and serum samples were taken after 6 months. Many low-molecular weight metabolites were identified by H-1 NMR spectra of rat urine. A decrease in citrate and an increase in ketone bodies, creatinine, DMA, DMG, TMAO, and taurine in the urine of the rats. receiving high doses were found by H-1 NMR spectra. These may mean that high-dosage of ChangLe impairs the specific region of liver and kidney, such as renal tubule and mitochondria. The decrease in citrate and the increase in succinate and alpha-ketoglutarate were attributed to a combination of the inhibition of certain citric acid enzymes, renal tubular acidosis and the abnormal fatty acid catabolism. The information of the renal capillary necrosis could be derived from the increase in DMIA, DMG and TMAO. The increase in taurine was due to hepatic mitochondria dysfunction. The conclusions were supported by the results of biochemical measure. merits and enzymatic assay.

Ultrafine fibers electrospun from biodegradable polymers

Biodegradable poly(I-lactide) (PLLA) and poly(e-caprolactone) (PCL) were electrospun into ultrafine fibers. The technological parameters influencing the spinning process and morphology of the fibers obtained were examined. These parameters included solvent composition, addition of certain organic salts, molecular weight and concentration of the polymers, capillary diameter, air ventilation, and pressure imposed on the surface of the solution as well as electrostatic field. By properly choosing and adjusting these parameters, submicron PLLA and PCL fibers with a narrow diameter distribution were prepared. Scanning electronic microscopy was used to observe the morphology and diameter size of the fibers.

Evaluation and application of micro-sampling system for inductively coupled plasma mass spectrometry

Two Meinhard microconcentric nebulizers, model AR30-07-FM02 and AR 30-07-FM005, were employed as a self-installed micro-sampling system for inductively coupled plasma-mass spectrometry (ICP-MS). The FM02 nebulizer at 22 muL/min of solution uptake rate gave the relative standard deviations of 7.6%, 3.0%, 2.7%, 1.8% for determinations (n = 10) of 20 mug/L Be, Co, In and Bi, respectively, and the detection limits (3s) of 0.14, 0.10, 0.02 and 0.01 mug/L for Be, Co In and Bi, respectively. The mass intensity of In-115 obtained by this micro-sampling system was 60% of that by conventional pneumatic nebulizer system at 1.3 mL/min. The analytical results for La, Ce, Pr and Nd in 20 muL Wistar rat amniotic fluid obtained by the present micro-sampling system were precisely in good agreement with those obtained using conventional pneumatic nebulization system.