An Efficient and Selective Oxidation of Sulfides and Thiols with Silica-Supported 1,1,3,3-Tetramethylguanidine/Br2 Complex

Silica-supported 1,1,3,3-tetramethylguanidine/Br₂ complex is an efficient reagent for the selective oxidation of aliphatic and aromatic sulfides to the corresponding sulfoxides and the oxidative coupling of thiols to disulfides in aqueous solution at room temperature in a short reaction time.     

SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF SOME NEW PYRIDO[3′,2′:4,5]THIENO[3,2-d]- PYRIMIDINE DERIVATIVES

5-Acetyl-3-amino-4-aryl-6-methylthieno[2,3-b]pyridine-2-carboxamides (1a, b) were reacted with aromatic aldehydes or with some cycloalkanones to give the corresponding tetrahydropyridothienopyrimidinone derivatives 2a–f and 4a–d . The reaction of compound 1b with urea and/or carbon disulfide has been carried out and their products were identified. Some representative compounds were screened in vitro for their antimicrobial activities.     

High-throughput micro-solid phase extraction on 96-well plate using dodecyl methacrylate-ethylen glycol dimethacrylate monolithic copolymer

A novel high-throughput device based on 96-micro-solid phase extraction (96-μ-SPE) system was constructed for multiresidue determination of nine pesticides in aquatic samples. The extraction procedure was performed on a commercially available 96-well plate system. The extraction module consisted of 96 pieces of 1 cm × 3 cm of cylindrically shaped stainless steel meshes. The prepared meshes were fixed in a home-made polytetrafluoroethylene-based constructed ninety-six holes block for possible simultaneous immersion of meshes into the center of individual wells. Dodecyl methacrylate and ethylene glycol dimethacrylate was copolymerized as a monolithic polymer and placed in the cylindrically shaped stainless steel meshes as extracting medium. A volume of 1 mL of the aquatic sample was transferred into the 96-well plate and the 96-μ-SPE device was applied for the extraction of the selected pesticides. Subsequently, the extracted analytes were analyzed by gas chromatography–mass spectrometry. Influential parameters such as polymer synthesis conditions, sorbent-to-sorbent reproducibility, ionic strength and extraction time were optimized. Intra and inter-sorbent reproducibility on 96-μ-SPE device were evaluated and results revealed that extraction yields are rather similar. Limits of detection were below 4 μg L⁻¹ and the coefficient of determination was satisfactory (r² > 0.99) for all the studied analytes. The developed method was successfully applied to the extraction and determination of the selected pesticides in surface water samples.     

Simple Synthesis of Highly Functionalized Ketenimines

The 1:1 reactive intermediate generated by the addition of alkyl isocyanides to dibenzoylacetylene or dialkyl acetylenedicarboxylates was trapped by fairly strong NH acids such as isatin, phthalimide, 4-nitroimidazole, or 2-benzoylimidazole to yield highly functionalized ketenimines.     

N-Hydroxyphthalimide-Catalyzed Oxidative Production of Phthalic Acids from Xylenes Using O2/HNO3 in an Ionic Liquid

A simple and mild process for oxidation of xylenes to phthalic acids using N-hydroxyphthalimide/O₂/HNO₃ in an ionic liquid, wherein the ionic liquid can be successfully recovered and reused, is described.     

Synthesis of nanocrystalline zinc manganese oxide by thermal decomposition of new dinuclear manganese(III) precursors

Nanocrystalline manganese-doped zinc oxide was synthesized by thermal decomposition of a zinc oxide sol with two new dinuclear manganese(III) complexes as precursor. Thermal analysis results indicated that the decomposition of manganese precursors occurred at 269 and 314 °C. X-ray structural analysis shows the presence of dimanganese core in the complexes and the binding of the ligands to the manganese(III) is through N₂O₂. The manganese-doped zinc oxide composite was characterized by means of X-ray diffraction, scanning electron microscopy, and UV–Vis spectroscopy. Structural properties of the composites elucidated that the manganese ions have substituted the zinc ions without changing the wurtzite structure of zinc oxide.     

Electrically enhanced liquid‐phase microextraction of three textile azo dyes from wastewater and plant samples

An electromembrane extraction procedure coupled with HPLC and visible detection was applied for the extraction of three textile azo dyes as organic salts. The extraction parameters such as extraction time, applied voltage, pH range, and concentration of salt added were optimized. A driving force of 60 V was applied to extract the analytes through 2‐nitrophenyl octyl ether, used as the supported liquid membrane, into a neutral aqueous solution. This method required 20 min extraction time from a neutral sample solution. The proposed microextraction technique provided good linearity with correlation coefficients from 0.996 to 0.998 over a concentration range of 1.0–1000.0 ng/mL. The LODs of dyes were 0.30–0.75 ng/mL, while the reproducibility ranged from 6.7 to 12.9% (n = 6). Also, enrichment factors of 96–162 that corresponded to the recoveries ranging from 48 to 81% were achieved. Finally, the application of this new method was demonstrated on wastewater samples and some plants grown in contaminated environments. Excellent selectivity was obtained as no interfering peaks were detected.     

In Vitro and In Vivo Enzyme‐Mediated Biomineralization of Oligo(poly(ethylene glycol) Fumarate Hydrogels

The enzyme alkaline phosphatase (ALP) is added at different concentrations (i.e., 0, 2.5, and 10 mg · ml^?1) to oligo(poly(ethylene glycol)fumarate) (OPF) hydrogels. The scaffolds are either incubated in 10 mM calcium glycerophosphate (Ca–GP) solution for 2 weeks or implanted in a rat subcutaneous model for 4 weeks. Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and alizarin red staining show a strong ability to form minerals exclusively in ALP‐containing hydrogels in vitro. Additionally, the calcium content increases with increasing ALP concentration. Similarly, only ALP‐containing hydrogels induce mineralization in vivo. Specifically, small (≈5–20 µm) mineral deposits are observed at the periphery of the hydrogels near the dermis/scaffold interface using Von Kossa and alizarin red staining.

     

Cyclodextrin Host‐Guest Recognition Approach for Simultaneous Quantification and Voltammetric Studies of Levodopa and Carbidopa in Pharmaceutical Products

An electrochemical sensor for simultaneous quantification of Levodopa (L‐dopa) and Carbidopa (C‐dopa) using a β‐cyclodextrin/poly(N‐acetylaniline) (β‐CD/PNAANI) modified carbon paste electrode has been developed. Preconcentrating effect of β‐CD as well as its different inclusion complex stability with L‐dopa and C‐dopa was used to construct an electrochemical sensor for quantification of these important analytes. The overlapping anodic peaks of L‐dopa and C‐dopa at 810 mV on bare carbon paste electrode resolved in two well‐defined voltammetric peaks at 450 and 880 mV vs. Ag/AgCl, respectively, with a drastic enhancement of the anodic peak currents. Under optimized conditions, linear calibration curves were obtained in the ranges of 0.5–117 µM and 1.6–210 µM with detection limits down to 0.2 and 0.8 µM for L‐dopa and C‐dopa, respectively. The proposed electrode was successfully applied for the determination of L‐dopa /C‐dopa in pharmaceutical formulations and the results were in close agreement with the labeled values.