Miscible blends of nitro‐substituted polybenzimidazole and polyetherimide

A novel blend system was prepared by blending organosoluble nitro‐substituted polybenzimidazole (NO₂‐PBI) and polyetherimide (PEI) in a cosolvent at a moderate condition. It was shown that the NO₂‐PBI/PEI blends not only possess tractable processability owing to the enhanced solubility of NO₂‐PBI but also retain the desirable features of unmodified PBI/PEI blends. Apparent miscibility in the blends was observed and attributed to hydrogen‐bonding interactions between N? H groups in NO₂‐PBI and carbonyl groups in PEI. It was revealed that the NO₂‐PBI/PEI blends phase‐separate upon heating above the glass‐transition temperatures. The observed mixing of NO₂‐PBI and PEI in a molecular level, although sustainable only in the glassy region, was shown to lend synergy effects to the physical properties of the blends. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1778–1783, 2001     

Synthesis of 2,3-disubstituted benzofurans on solid-support

A library of 2,3-disubstituted benzofuran scaffold was developed by using intramolecular Wittig olefination and Friedel-Crafts acylation.     

Simultaneous determination of sibutramine and its active metabolites in human plasma by LC‐MS/MS and its application to a pharmacokinetic study

A simple and sensitive liquid chromatography–electrospray ionization–tandem mass spectrometry (LC‐ESI‐MS/MS) technique was developed and validated for the determination of sibutramine and its N‐desmethyl metabolites (M1 and M2) in human plasma. After extraction with methyl t‐butyl ether, chromatographic separation of analytes in human plasma was performed using a reverse‐phase Luna C₁₈ column with a mobile phase of acetonitrile–10 mm ammonium formate buffer (50:50, v/v) and quantified by ESI‐MS/MS detection in positive ion mode. The flow rate of the mobile phase was 200 μL/min and the retention times of sibutramine, M1, M2 and internal standard (chlorpheniramine) were 1.5, 1.4, 1.3 and 0.9 min, respectively. The calibration curves were linear over the range 0.05–20 ng/mL, for sibutramine, M1 and M2. The lower limit of quantification was 0.05 ng/mL using 500 μL of human plasma. The mean accuracy and the precision in the intra‐ and inter‐day validation for sibutramine, M1 and M2 were acceptable. This LC‐MS/MS method showed improved sensitivity and a short run time for the quantification of sibutramine and its two active metabolites in plasma. The validated method was successfully applied to a pharmacokinetic study in human. Copyright © 2011 John Wiley & Sons, Ltd.     

Simultaneous Separation and Determination of Isosorbide Dinitrate and Isosorbide 5-Mononitrate in Human Plasma by LC–MS–MS

A sensitive, selective, and simple liquid chromatography-tandem mass spectrometry method has been developed for the simultaneous separation and determination of isosorbide dinitrate and its active metabolite, isosorbide 5-mononitrate, in human plasma. Topiramate was used as the internal standard. Sample preparation consisted of a simple one-step liquid–liquid extraction with ethylacetate without pH adjustment. The method was fully validated with respect to linearity, sensitivity, specificity, recovery, accuracy, and precision. Isosorbide dinitrate and isosorbide 5-mononitrate were stable in standard solution and in plasma samples under storage and processing conditions. The assay was successfully applied to the pharmacokinetic study of isosorbide dinitrate and isosorbide 5-mononitrate in human plasma.     

Mechanical properties of titania nanofiber mats fabricated by electrospinning of sol–gel precursor

Flexible mats of titania fibers are prepared by calcination of electrospun polyvinylpyrrolidone fibers containing titanium isopropoxide precursor. Structural investigation of the calcinated nanofibers by X-ray diffraction (XRD) and electron diffraction (ED) combined with the morphologies by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show the titania fibers, with an average diameter of 180 nm, were comprised of anatase and rutile crystals. The mechanical, chemical and thermal properties of the titania fiber mats are further investigated by the techniques of Instron mechanical tester, thermogravimetric analyzer (TGA), and Fourier transform infrared spectroscopy (FT-IR). The titania fiber mat prepared in this method exhibited a significant flexibility with 461 MPa Young’s modulus.