Preparation and characterization of poly (acrylic acid-dimethylaminoethylmethacrylate) as amphoteric exchange resin and its adsorption properties

Poly (acrylic acid-dimethylaminoethylmethacylate) resin was prepared by copolymerization technique. Gamma irradiation as initiator was used for the polymerization process. Obtained polymeric resin is an amphoteric ion exchange resin in which a quaternary ammonium group and a carboxyl group are incorporated on a cross-linked polymer frame. The physicochemical properties of obtained polymeric resin were determined using inductively coupled plasma (ICP), Fourier transform infrared spectroscopy (FTIR), TGA-DTA, and scanning electron microscope (SEM). Ion-exchange capacity (IEC), thermal stability, distribution behavior, etc. were also carried out to understand the adsorption behavior of the material. The equilibrium data were analyzed by the Langmuir and Freundlich isotherm models. The kinetic models’ data with zinc ions were studied.     

A Short and Convenient Synthesis of 5-Alkyl Substituted 8-Hydroxyquinolines

5-Chloro-8-methoxyquinoline undergoes rapid and reversible lithium-halogen exchange reaction with alkyllithiums to yield 5-alkyl substituted derivatives indirectly, whereas the reaction with phenyllithium is slower and 5-alkyl substituted compounds are formed by the direct addition of alkyl halides.     

HIGH YIELD SYNTHESIS OF α-ALKOXYPHOSPHONIUM SALTS AND α-ALKOXYPHOSPHONATES

Abstract

The recent work of Ley et al. ¹ on α-alkoxyphosphorane compounds from cyclic enolethers has prompted us to report our findings in this area. In addition to cyclic enol ethers we have studied the acyclic case as well as the use of phosphite in place of triphenylphosphine. Using this approach we have prepared alkoxy-as well as 5-and 6-membered oxyheterocyclic phosphonium salts and phosphonates in high yield.     

Separation and determination of ciprofloxacin in seawater,human blood plasma and tablet samples using molecularly imprinted polymer pipette‐tip solid phase extraction and its optimization by response surface methodology

By synthesizing a molecular imprinted polymer as an efficient adsorbent, ciprofloxacin was micro‐extracted from seawater, human blood plasma and tablet samples by pipette‐tip micro solid phase extraction and determined spectrophotometrically. Response surface methodology was applied with central composite design to build a model based on factors affecting on microextraction of ciprofloxacin; including volume of eluent solvent, number of extraction cycles, number of elution cycles, and pH of sample. Other factors that affect extraction efficiency, such as type of eluent solvent, volume of sample, type, and amount of salt were optimized with one‐variable‐at‐a‐time method. Under optimum extraction condition, pH of sample solution was 7.0, volume of eluent solvent (methanol) was 200 µL, volume of sample solution was 10 mL, and the number of extraction and elution cycles was five and seven, respectively, amount of Na₂SO₄ (as salt) and MIP (as sorbent) were optimized at 150 and 2 mg, respectively. The linear range of the suggested method under optimum extraction factors was 5–150 µg/L with a limit of detection of 1.50 µg/L for the analyte. Reproducibility of the method (as relative standard deviation) was better than 7%.     

Separation of zinc from aqueous samples using a molecular imprinting technique

In this article, the separation of zinc from aqueous samples by solid-phase extraction based on a molecular imprinting technique is described. Zn-imprinted polymer was prepared by free radical solution polymerisation in a glass tube containing ZnSO₄, morin, 4-vinylpyridine as a functional monomer, ethyleneglycoldimethacrylate as a cross-linking monomer, and 2,2′-azobisisobutyronitrile as an initiator. The obtained polymer block was ground and sieved (55–75 µm) and the Zn–morin complex was separated from polymer particles by leaching with 2M HCl. The synthesised polymer particles have been characterised by IR and differential scanning calorimetric studies either before or after leaching. The effects of different parameters, such as pH, adsorption and desorption time, type and minimum amount of the eluent for elution of the complex from polymer were evaluated. Extraction efficiency more than 99% was obtained by elution of the polymers with 10 mL of CH₂Cl₂–dimethyl sulfoxide (1 : 1, v/v). The detection limit of the proposed method was 2.9 µg L^?1. A dynamic linear range in the range of 25–200 µg L^?1 was obtained. The relative standard deviation was found to be below 9.2%. In addition, the influence of various cationic and anionic interferences on the complex recovery was studied. The method was applied to the recovery and determination of Zn in a few different real samples.     

3-D Quantum Transport Solver Based on the Perfectly Matched Layer and Spectral Element Methods for the Simulation of Semiconductor Nanodevices

A 3-D quantum transport solver based on the spectral element method (SEM) and perfectly matched layer (PML) is introduced to solve the 3-D Schr?dinger equation with a tensor effective mass. In this solver, the influence of the environment is replaced with the artificial PML open boundary extended beyond the contact regions of the device. These contact regions are treated as waveguides with known incident waves from waveguide mode solutions. As the transmitted wave function is treated as a total wave, there is no need to decompose it into waveguide modes, thus significantly simplifying the problem in comparison with conventional open boundary conditions. The spectral element method leads to an exponentially improving accuracy with the increase in the polynomial order and sampling points. The PML region can be designed such that less than -100 dB outgoing waves are reflected by this artificial material. The computational efficiency of the SEM solver is demonstrated by comparing the numerical and analytical results from waveguide and plane-wave examples, and its utility is illustrated by multiple-terminal devices and semiconductor nanotube devices.     

Ruthenium Nanoparticles Intercalated in Hectorite: A Reusable Hydrogenation Catalyst for Benzene and Toluene

The cationic organometallic aqua complexes formed by hydrolysis of [(C₆H₆)RuCl₂]₂ in water, mainly [(C₆H₆)Ru(H₂O)₃]²⁺, intercalate into sodium hectorite by ion exchange, replacing the sodium cations between the anionic silicate layers. The yellow hectorite thus obtained reacts in ethanol with molecular hydrogen (50 bar, 100°C) with decomposition of the organometallic aqua complexes to give a black material, in which ruthenium(0) nanoparticles (9–18 nm) are intercalated between the anionic silicate layers, the charges of which being balanced by hydronium cations. The black ruthenium-modified hectorite efficiently catalyses the hydrogenation of benzene and toluene in ethanol (50 bar H₂, 50°C), the turnover frequencies attaining 7000 catalytic cycles per hour. Dedicated to Professor Günter Schmid, pioneer of nanocluster chemistry, on the occasion of his 70th birthday     

D-boundedness andD-compactness in finite dimensional probabilistic normed spaces

In this paper, we prove that in a finite dimensional probabilistic normed space, every two probabilistic norms are equivalent and we study the notion ofD-compactness and D-boundedness in probabilistic normed spaces.     

Development and Validation of a Stability Indicating HPLC Method for Determination of Granisetron

The aim of this study was to study the stress degradation of granisetron and analysis of the drug in the presence of its degradation products. Forced degradation studies were conducted on bulk sample using acidic, alkaline, oxidative, heat and photolytic conditions. Granisetron was relatively unstable under acidic, alkaline and oxidative conditions. Separation of granisetron and degradation products was achieved using a Nova‐Pak C₈ column and acetonitrile‐KH₂PO₄ 25 mM (75:25, v/v) as mobile phase with UV detection at 305 nm. The method was linear over the range of 0.2‐15 μg/mL granisetron (r² > 0.999). The within‐day and between‐day precision values were also in the range of 0.5‐4%. The proposed method was successfully applied for quantitative determination of granisetron in tablets and in vitro dissolution studies.     

Endo-inulinase Stabilization by Pyridoxal Phosphate Modification: A Kinetics, Thermodynamics, and Simulation Approach

The structural and storage and functional thermostabilization of endo-inulinase (EC 3.2.1.7) through semi-rational modification of surface accessible lysine residues by pyridoxal-5'-phosphate (PLP) and ascorbate reduction have been explored. Improved stability was observed on modifications in the absence or presence of inulin, which indicates storage or functional thermostabilization, respectively. Comparisons have been made between non-modified and modified enzyme by the determination of Tm as an indicator of structural stability, temperature-dependent half-lives (t1/2), energy barrier of the inactivation process, and thermodynamic parameters (ΔH, ΔG, and ΔS) in a storage thermostability approach. These parameters coincided well with the observed stabilization of the engineered enzyme. Moreover, relative activities with sucrose and inulin were determined for non-modified and modified endo-inulinases at different temperatures. A comparison of the sucrose-to-inulin ratios of the initial rate of hydrolysis as an indicator of substrate specificity revealed about twofold improvement in inulinase versus sucrose activity by enzyme modification. Molecular dynamics simulations and molecular docking approaches were employed to explain the observed structural and functional thermostabilization of endo-inulinase upon modification. We hypothesize the establishment of intramolecular interactions between the covalently attached PLP-Lys381 and Arg526 and Ser376 residues as a representative of modification-originated intramolecular contacts in the modified enzyme.