Influence of process parameters on the epoxidation of 2-buten-1-ol over titanium silicalite TS-1 catalyst

The influence of process parameters on the epoxidation of 2-buten-1-ol with 30 % hydrogen peroxide using the titanium silicalite TS-1 is presented. The studies were carried out under autogenic pressure (in autoclave). Methanol was used as a solvent in this process. The influence of temperature, 2-buten-1-ol to hydrogen peroxide mole ratio, amount of solvent used, TS-1 catalyst content, and reaction time on the reaction was studied. The major product of this reaction, 2,3-epoxybutan-1-ol (EB), has numerous applications in chemical industry.     

Photochemical mineralization of europium, titanium, and iron oxyhydroxide nanoparticles in the ferritin protein cage

The Fe storage protein ferritin was used as a size-constrained reaction vessel for the photoreduction and reoxidation of complexed Eu, Fe, and Ti precursors for the formation of oxyhydroxide nanoparticles. The resultant materials were characterized by dynamic light scattering, gel electrophoresis, UV-vis spectroscopy, and transmission electron microscopy. The photoreduction and reoxidation process is inspired by biological sequestration mechanisms observed in some marine siderophore systems.     

Difluoromethyltrialkylammonium salts--their expeditious synthesis from chlorodifluoromethane and tertiary amines in the presence of concentrated aqueous sodium hydroxide. The catalytic process

We found that difluorocarbene generated from chlorodifluoromethane with 50% aqueous sodium hydroxide reacts with lipophilic tertiary amines 1a-g giving difluoromethyltrialkylammonium chlorides 2a-g in high yields. Similarly, difluoromethyltrialkylammonium iodides 3h-l, nitrates 4h-k, or isothiocyanates 5i,j were synthesized from hydrophilic tertiary amines 1h-l and the corresponding sodium or potassium salts. The process is catalytic with respect to the base used.     

Multi-Class Procedure for Analysis of 50 Antibacterial Compounds in Eggshells Using Ultra-High-Performance Liquid Chromatography–Tandem Mass Spectrometry

In this work, for the first time, Ultra-High-Performance Liquid Chromatography–Tandem Mass Spectrometry (UHPLC–MS/MS) method was developed for qualitative and quantitative analysis of veterinary antibiotics (cephalosporins, diaminopyrimidines, fluoro(quinolones), lincosamides, macrolides, penicillins, pleuromutilins, sulfonamides, tetracyclines, and sulfones) in hen eggshells. The sample preparation method is based on a liquid–liquid extraction with a mixture of metaphosphoric acid, ascorbic acid, EDTA disodium salt dihydrate, and acetonitrile. The chromatographic separation was performed on Luna^® Omega Polar C18 10 column in gradient elution mode and quantitated in an 8 min run. Validation such as linearity, selectivity, precision, recovery, matrix effect, limit of quantification (LOQ), and limit of detection (LOD) was found to be within the acceptance criteria of the validation guidelines of the Commission Decision 2002/657/EC and EUR 28099 EN. Average recoveries ranged from 81–120%. The calculated LOQ values ranged from 1 to 10 µg/kg, the LOD values ranged from 0.3 to 4.0 µg/kg, depending on analyte. The developed method has been successfully applied to the determination of antibacterial compounds in hen eggshell samples obtained from different sources. The results revealed that enrofloxacin, lincomycin, doxycycline, and oxytetracycline were detected in hen eggshell samples.     

A Comparison of Edge-plane and Basal-plane Pyrolytic Graphite Electrodes towards Sensitive Determination of the Fungicide Mandipropamid

A sensitive square-wave voltammetry (SWV) method based on basal-plane pyrolytic graphite electrode (BPPGE) and edge-plane pyrolytic graphite electrode (EPPGE) was developed to determine the concentration of the pesticide mandipropamid (MAN) in spiked river water and grape juice samples. Under optimal experimental conditions, the SWV response of EPPGE and BPPGE was linear over the concentration ranges of 0.7 to 9.0 μmol L⁻¹ and 0.5 to 10.0 μmol L⁻¹, respectively. The method was successfully used to determine MAN in spiked samples with good recovery. Cyclic voltammetry (CV) was conducted to understand the mechanism underlying the electrode process of MAN.     

Thermal Decomposition of Carbamoyl Meldrum's Acids: A Starting Point for the Preparation of 1,3‐Oxazine Derivatives

The ability to undergo [4 + 2] versus [2 + 2] cycloaddition was under investigation for ketenes thermally generated from carbamoyl Meldrum's acid. Usually, 1,3‐oxazino‐5‐carbamoylo‐4,6‐diones are formed when carbamoyl Meldrum's acid reacts with imine. However, in some cases, a reaction takes an unexpected course, leading to the formation of tetraponerines alkaloids derivatives or cyclic iminoethers.     

Influence of the charge distribution on the stationary phases zeta potential

A set of seven home‐made silica based bonded phases with different functional groups was investigated. Their zeta potential data in methanol and acetonitrile as well as in methanol/water and acetonitrile/water solution were obtained by using a Zetasizer. The influence of polar functional groups on a zeta potential was investigated. The results show that the amines incorporated in the structure of chemically bonded phases of reversed‐phase materials are protonated during chromatographic analysis, resulting in changes of the zeta potential from negative to positive values. Acetonitrile causes more negative values and methanol provides positive (or less negative) values of the zeta potential.     

Analysis of nonlocal model of compressible fluid in 1‐D

We study a nonlocal modification of the compressible Navier–Stokes equations in mono‐dimensional case with a boundary condition characteristic for the free boundaries problem. From the formal point of view, our system is an intermediate between the Euler and Navier–Stokes equations. Under certain assumptions, imposed on initial data and viscosity coefficient, we obtain the local and global existence of solutions. Particularly, we show the uniform in time bound on the density of fluid. Copyright © 2010 John Wiley & Sons, Ltd.     

A bienzymatic amperometric immunosensor exploiting supramolecular construction for ultrasensitive protein detection

Self-assembly of a ferrocene-appended polymer bearing an antigen fragment and lactate oxidase on a cyclodextrin-modified surface provides a highly sensitive, easy-to-operate and self-sufficient immunosensor.     

Automatic scatter detection in fluorescence landscapes by means of spherical principal component analysis

In this paper, we introduce a new method, based on spherical principal component analysis (S‐PCA), for the identification of Rayleigh and Raman scatters in fluorescence excitation–emission data. These scatters should be found and eliminated as a prestep before fitting parallel factor analysis models to the data, in order to avoid model degeneracies. The work is inspired and based on a previous research, where scatter removal was automatic (based on a robust version of PCA called ROBPCA) and required no visual data inspection but appeared to be computationally intensive. To overcome this drawback, we implement the fast S‐PCA in the scatter identification routine. Moreover, an additional pattern interpolation step that complements the method, based on robust regression, will be applied. In this way, substantial time savings are gained, and the user's engagement is restricted to a minimum, which might be beneficial for certain applications. We conclude that the subsequent parallel factor analysis models fitted to excitation–emission data after scatter identification based on either ROBPCA or S‐PCA are comparable; however, the modified method based on S‐PCA clearly outperforms the original approach in relation to computational time. Copyright © 2013 John Wiley & Sons, Ltd.