Characterization and Transport Properties of Surfactant-Templated Silica Layers for Membrane Applications

An intermediate surfactant-templated silica (STS) layer is applied between the supporting mesoporous γ-Al₂O₃ and the amorphous microporous silica overlayer resulting in dual-layered microporous silica membranes for gas separation applications that show improved values for both hydrogen flux and selectivity. Determination of thickness and porosity of as-deposited membrane layers by spectroscopic ellipsometry reveals that the STS layer is present as a distinctive layer of ～20 nm thickness, with penetration up to a depth of ～70 nm into the underlying γ-Al₂O₃support layer, whose thickness and porosity are determined to be 1.3 μm and 50%, respectively.     

Quantitative analysis of bucillamine in blood using high-performance liquid chromatography-mass spectrometry technique

A fast and sensitive method has been developed and validated for the determination of bucillamine in human blood by derivatizing the free sulfhydryl groups with isobutyl acrylate (IA), by APCI-LC/MS/MS. The collected blood sample was immediately mixed with a mixture of IA and 0.05 m Tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer, pH 9.2, to stabilize the sulfyhydryl moieties. The derivatized samples were then extracted by protein precipitation, evaporated, reconstituted and injected using an LC-APCI/MS/MS instrument. Separation was achieved using a C18 analytical column and a gradient mobile phase within a chromatographic run time of 5 min. A quadratic (weighted 1/concentration(2)) relationship was observed during validation over a concentration range of 0.4-40 microg/mL with a correlation value of r > or = 0.9966. The inter-batch precision and accuracy at low, medium and high concentrations were 8.1, 8.4 and 7.3%; 113.3, 104.9 and 103.9%, respectively, and the intra-batch precision and accuracy at low, medium and high concentrations were 7.7, 5.4 and 2.7%; 105.1, 111.9 and 113.2%, respectively.     

Tailored noise waveform/collision-induced dissociation of ions stored in a linear ion trap combined with liquid chromatography/Fourier transform ion cyclotron resonance mass spectrometry

A new collision-induced dissociation (CID) technique based on broadband tailored noise waveform (TNW) excitation of ions stored in a linear ion trap has been developed. In comparison with the conventional sustained off-resonance irradiation (SORI) CID method commonly used in Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), this MS/MS technique increases throughput by eliminating the long pump-down delay associated with gas introduction into the high vacuum ICR cell region. In addition, the TNW-CID method speeds spectrum acquisition since it does not require Fourier transformation, calculation of resonant frequencies and generation of the excitation waveforms. We demonstrate TNW-CID coupled with on-line capillary reverse-phase liquid chromatography separations for the identification of peptides. The experimental results are compared with data obtained using conventional quadrupole ion trap MS/MS and SORI-CID MS/MS in an ICR cell.     

Ethyl 3‐amino‐6‐phenyl‐4‐tolylthieno[2,3‐b]pyridine‐2‐carboxylate

In the title compound, C₂₃H₂₀N₂O₂S, the central thieno­pyridine ring system is essentially planar, the dihedral angle between the planes of the two rings being 0.3 (2)°. The terminal ethyl carboxyl­ate group is twisted by 26.7 (3)° away from the central ring system. A short intramolecular hydrogen bond involving the amino N atom and the carbonyl O atom [N⋯O = 2.806 (4) Å] forms a pseudo‐six‐membered ring. Significant intermolecular C—H⋯N, C—H⋯O and C—H⋯π interactions contribute strongly to the stability of the structure, along with weak π–π‐stacking interactions.     

Microwave Activated Solid Support Synthesis of New Antibacterial Quinolones

Summary.  A novel synthesis of 6-fluoro-7-(5-aryl-1,3,4-thiadiazol/oxadiazol-2-yl-sulfanyl)-4-quinolone-3-carboxylic acids from 7-chloro-6-fluoro-4-quinolone-3-carboxylic acid and 5-substituted 1,3,4-thiadiazoles/oxadiazoles on basic alumina under microwave activation is described. All compounds were screened for their in vitro antibacterial activity against B. lichenformis, 2689, K. aerogens 2281, S. typhimurium 2501, E. herbicola 2491, and P. vulgaris 2027 and found to possess activities comparable to that of the standard drug norfloxacin. Received May 2, 2000. Accepted (revised) June 13, 2000     

Some properties of aqueous xanthan gels formed under the action of aluminium(III) ions

Aqueous xanthan solutions form gels when aluminium salts are added and the solutions are heated above 45 °C. The gelation process was followed by dynamic light scattering. Characterization was based on the heterodyne and nonergodic approaches. Both techniques gave the same fast relaxation times, but for the slow motion much larger values were found in the heterodyne than in the nonergodic approach. The heterodyne fraction 1-X was found to correlate closely with the plateau height of the time correlation function (TCF) at large delay times in the nonergodic experiments. Three methods of gel point determination are demonstrated: (i) onset of heterodyne/nonergodic behavior, (ii) observation of a sharp maximum for the fast relaxation time at the gel point, (iii) observation of power-law behavior of the TCF. The statistics of nonergodic fluctuations were examined and evaluated. The potential of this procedure for detailed structure evaluation of inhomogeneities in the gel is emphasized.     

Synthesis and characterization of homologous series with chiral (S)-1-methylpropyl terminal substituent

Homologous series of liquid crystalline azoesters and azomethine esters consisting of a (S)-1-methylpropyl group attached in one of the terminal positions have been synthesized and thermally characterized. All twenty-four derivatives from both series, namely, the 4-(4-n-alkoxybenzoyloxy)-4'-1-(S)-methylpropylazobenzenes and 4-(4-n-alkoxybenzoyloxy)benzylidene-4'-1-(S)-methylpropylanilines exhibit mesomorphism. The lower members of the homologous series show a chiral nematic phase while the higher members show smectic C*, smectic A as well as chiral nematic mesophases. The homologues have been characterized using IR, NMR and UV-Visible, spectroscopies, X-ray diffraction and DSC. Their mesomorphic properties are compared with those of structurally related homologous series.