Isolation and determination of toxic congeners of polychlorinated biphenyls in environmental samples

A Method has been developed for the separation and enrichemen of there non-ortho, eight mono-ortho, and di-ortho substituted polychlorinated biphenyls (PCBs) from Aroclor formulations and environmental samples. The fractionation is accomplished using high performance liquid chromatography (HPLC) with a 2-(1-pyrenyl)ethyldimethylsilysily silca column. GC-MSD with an optimized temperature program was used for quantitation, Hexane, pentane, cyclohexane, iso-octane, and 2-propanol were tested as a mobile phase for the isolation of the thirteen target PCBs in a Aroclor 1242, 1254, and 1260 (1:1:1) misture, Pentane at room temperature with a slow rate of 0.7 ml/min is the condition of choice. The average recovery of thirteen target PCBs spiked in the Aroclor mixture is 99.5% with an average relative standard deviation of 4.5%. The average method detection limit is 8pg/μl. Targer PCBs in the reference solis, incinarator ash, and sediment samples were measured.     

A Semiempirical Study of Carbon Nanotubes with Finite Tubular Length and Various Tubular Diameters

A semiempirical PM3 quantum computational method has been used to generate the electronic and optimized geometrical structure of SWNT of zigzag and armchair types. We shed light on the electronic structures of SWNT with various diameters and lengths of the tube. Particularly, the calculated HOMO, LUMO and band‐gap of SWNT are not monotonic but exhibit a well‐defined oscillation, which depends on the tubular diameter and the tubular length. Calculated HOMO, LUMO and band‐gap of the zigzag SWNTs have oscillated with tubular diameter as they contain an odd or even number of benzenoids in the circular plane of the carbon nanotube. The zigzag SWNTs with an odd number of benzenoids have a higher band‐gap than those of SWNTs with an even number of benzenoids in the circular plane of the carbon nanotube. Calculated results also reveal that the tubular length in the zigzag SWNTs influences the band‐gaps very little. For the armchair SWNT, calculated HOMO, LUMO and band‐gap contained the oscillate depending on the number of carbon sections in the tubular length axis. Their repeat sections are 3n‐1, 3n and 3n+1. The armchair SWNT with 3n+1 sections has a high band‐gap while the SWNTs with 3n‐1 sections have a low band‐gap. The tubular diameters of armchair SWNT influence the HOMO, LUMO and band gap very little.     

Chemical constituents of Antrodia camphorata submerged whole broth

One new compound, 10-hydroxy-gamma-dodecalactone (1) and three natural new compounds, 11-hydroxy-gamma-dodecalactone (2), 2-(2-hydroxyethyl)phenol (3) and 12-hydroxydodecanoic acid methyl ester (4), together with eight known compounds, ergostatrien-3beta-ol, ergosterol peroxide, methyl (4-hydroxyphenyl)acetate, vanillin, 4-hydroxybenzaldehyde, hexadecanoic acid, 5-methoxymethylfuran-2-carbaldehyde and 5-hydroxymethylfuran-2-carbaldehyde, all were isolated from the submerged whole broth of Antrodia camphorata. The structures of 1 and 2 were principally elucidated by spectral evidence and the absolute configuration was elucidated by the modified Mosher's method.     

Composite nano-titanium oxide-chitosan artificial skin exhibits strong wound-healing effect-an approach with anti-inflammatory and bactericidal kinetics

A composite nano-TiO2-chitosan with collagen artificial skin (NTCAS) showed promising characteristics of moderate water absorptivity (110 wt.-%), fine thickness (0.34 mm), low density (0.33 mg x mm(-3)), moderate biodegradability (<3.0%), and favorable time-dependent biodegradability (0.0521 mg x mL(-1) x h(-1) on Day 0; 0.0006 mg x mL(-1) x h(-1)on Day 3 post covering). More importantly, it showed uniquely potent bactericidal (sterilization) property with relatively large values of pseudo first-order kinetic coefficients (0.1736-0.0360 min(-1)) for TiO2 contents ranging from 2.63 x 10(-5) to 2.11 x 10(-4) mg x cm(-2). In wounded subjects, NTCAS showed a steady level of TNF-alpha, while the IL-6 level reached a peak on Day 7, although significantly lower than in the control and Duoderm groups. In the animal model, NTCAS showed better and faster recovery than the other groups, which can be attributed to the unique bactericidal effect of nano-TiO2 and immune-enhancing effect of chitosan. NTCAS is a promising artificial skin substitute and is superior to any other market product currently in use.     

Controlled shrinkage and re-expansion of a single aqueous droplet inside an optical vortex trap

This paper describes the shrinkage and re-expansion of individual femtoliter-volume aqueous droplets that were suspended in an organic medium and held in an optical vortex trap. To elucidate the mechanism behind this phenomenon, we constructed a heat- and mass-transfer model and carried out experimental verifications of our model. From these studies, we conclude that an evaporation mechanism sufficiently describes the shrinkage of aqueous droplets held in a vortex trap, whereas a mechanism based on the supersaturation of the organic phase by water that surrounds the droplet adequately explains the re-expansion of the shrunk droplet. The proposed mechanisms correlated well with experimental observations using different organic media, when H2O was replaced with D2O and when an optical tweezer was used to induce droplet shrinkage rather than an optical vortex trap. For H2O droplets, the temperature rise within the droplet during shrinkage was on the order of 1 K or less, owing to the rapid thermal conduction of heat away from the droplet at the microscale and the sharp increase in solubility for water by the organic phase with slight elevations in temperature. Because most chemical species confined to droplets can be made impenetrable to the aqueous/organic interface, a change in the volume of aqueous droplets translates into a change in concentration of the dissolved species within the droplets. Therefore, this phenomenon should find use in the study of fundamental chemical processes that are sensitive to concentration, such as macromolecular crowding and protein nucleation and crystallization.     

Simultaneous Separation of Four Types of Steroid Hormones by Micellar Electrokinetic Chromatography with Cetyltrimethylammonium Bromide

Micellar electrokinetic chromatography (MEKC) using a cationic surfactant, cetyltrimethylammonium bromide (CTAB), was applied to simultaneous separation of four types of hydrophobic steroid hormones including androgens, estrogens, progestins, and glucocorticoids. Various parameters, such as the concentration of CTAB, type and proportion of organic modifiers, and sample matrix have been demonstrated to be important with respect to the separation resolution, analysis time, and repeatability. Successful separation of cortisone, hydrocortisone, estriol, testosterone, estrone, progesterone, and estradiol was achieved at ?25 kV using 100 mM Tris‐boric acid buffer (pH 9.0) containing 40 mM CTAB and 20% 2‐propanol using ultraviolet (UV) absorption detection. For estrogen compounds which possess intrinsic fluorescence, detection limits at the sub μM level could be achieved with laser‐induced fluorescence (LIF) detection. Two kinds of pharmaceutical preparations were analyzed using the developed method, and the results were in good agreement with the label claims.     

Exfoliation of smectite clays by branched polyamines consisting of multiple ionic sites

Exfoliation through an ionic exchange reaction of layered silicate clays, including synthetic fluorinated mica (Mica) and natural montmorillonite (MMT), were achieved by using polyvalent amine salts as the intercalating agents. The requisite polyamine was synthesized from the epoxy/amine coupling reaction, involving a trifunctional poly(oxypropylene)-triamine (ca. 440 g/mol M_w) and diglycidyl ether of bisphenol-A. The polyamine was a mixture of oligomeric adducts consisting of multiple amine functionalities and a branched backbone. Partial acidification by HCl addition generated a series of amine salts that affected the intercalation and the expansion of the silicate interlayer in the range of 15.2-60.0 Å XRD d spacing. At the specific acidified ratio (H⁺/amine = 1/3 equiv ratio), the polyamine salts rendered the clay’s layered structure into randomization. The result was confirmed by using XRD and transmission electronic microscopy (TEM). The hybrids of polyamines and Mica or MMT were blended into epoxy resins and cured into nanocomposites, which exhibited the improvements of thermal stability and hardness.     

Effect of P/Si polymeric silsesquioxane and the monomer compound on thermal properties of epoxy nanocomposite

The unique polymeric silsesquioxane/4,4′-diglycidyether bisphenol A (DGEBA) epoxy nanocomposites have been prepared by sol-gel method. The structure of nanocomposites was characterized by attenuated total reflectance (ATR) and solid state ²⁹Si NMR. The characteristic intensity of trisubstituted (T) structure was higher than that of tetrasubstituted (Q) structure from solid state ²⁹Si NMR spectra of 3-isocyanatopropyltriethoxysilane (IPTS) modified epoxy. The activation energies of curing reaction of epoxy system and IPTS modified epoxy system are 28-66 kJ/mol and 57-75 kJ/mol, respectively, by Ozawa’s and Kissinger’s methods. The triethyoxysilane side chain of IPTS modified epoxy might interfere the curing reaction of epoxy/amine and increase the activation energy of curing. The thermal degradation of nanocomposites was investigated by Thermogravimetric analysis (TGA). The char yield of nanocomposites was proportional to the 2-(diphenylphosphino)ethyltriethoxysilane (DPPETES) moiety content at high temperature. A higher char content could inhibit thermal decomposition dramatically and enhance the thermal stability. Moreover, the nanocomposites possess high optical transparency.     

Reactions of the (2-pyridyl) pyrrolide platinum(II) complex driven by sterically encumbered chelation: a model for the reversible attack of alcohol at the coordinated carbon monoxide

Treatment of 3,5-bis(trifluoromethyl)-2-(2'-pyridyl)pyrrole (fpyroH) with Pt(DMSO)2Cl2 and Na2CO3 in THF solution gave a light-yellow complex denoted as [Pt(fpyro)2] (1). A single-crystal X-ray diffraction study on 1 revealed a large conformational distortion around the platinum(II) center, which is attributed to interligand repulsion between the pyridyl groups and the CF3 substituents of the nearby pyrrolides. Reaction of 1 with N- and C-donor ligands such as acetonitrile, pyridine, isocyanide, and CO affords the adducts [Pt(fpyro)2(L)], L = NCMe (2), pyridine (3), CNBut (4), and CO (5), showing formation of one monodentate fpyro ligand by release of the strain energy. The variable-temperature 1H NMR studies showed a static structure for the N-substituted adducts 2 and 3, whereas the C-adducts 4 and 5 are shown to be more labile, displaying a pairwise exchange of bidentate and monodentate fpyro ligands in solution. Addition of ethanol to the coordinated CO in 5 during recrystallization is also established, affording an ethoxycarbonyl complex [Pt(fpyro)(fpyroH)(CO2Et)] (6), which was isolated as a crystalline solid and can be readily converted back to 5 and free ethanol upon dissolution at room temperature.