Modified Eu3+ doped Y2O3 Nanoparticles as Turn-on Fluorescence Sensor for Sensitive Determination of Methamphetamine

Journal of Analytical Chemistry - In this article, a new spectrofluorometric method was developed for the determination of methamphetamine based on a turn-on luminescence response of captopril...     

A sensitive and efficient method for trace analysis of some phenolic compounds using simultaneous derivatization and air‐assisted liquid–liquid microextraction from human urine and plasma samples followed by gas chromatography–nitrogen phosphorous detection

In present study, a simultaneous derivatization and air‐assisted liquid–liquid microextraction method combined with gas chromatography–nitrogen phosphorous detection has been developed for the determination of some phenolic compounds in biological samples. The analytes are derivatized and extracted simultaneously by a fast reaction with 1‐flouro‐2,4‐dinitrobenzene under mild conditions. Under optimal conditions low limits of detection in the range of 0.05–0.34 ng mL^?1 are achievable. The obtained extraction recoveries are between 84 and 97% and the relative standard deviations are less than 7.2% for intraday (n = 6) and interday (n = 4) precisions. The proposed method was demonstrated to be a simple and efficient method for the analysis of phenols in biological samples. Copyright © 2015 John Wiley & Sons, Ltd.     

A Method for the Acetylation of Alcohols Catalyzed by Heteropolyoxometallates

Summary. Esterifications of acetic acid with some linear, secondary, tertiary, and benzylic alcohols mediated by catalytic amounts of Keggin, Wells–Dawson, and Preyssler type heteropolyacids were carried out under reflux at mild reaction conditions with good to excellent yields. Among the examined catalysts, H₃PW₁₂O₄₀ and H₁₄NaP₅W₃₀O₁₁₀ revealed better results than other heteropolyacids. This work was performed with the aim of simplifying the esterification process by omitting any solvents and mineral acid catalysts. Easy work-up, low cost, and acidic waste reduction, which are all important features from the environmental and economical points of view, are distinct aspects of this protocol. Heteropolyacid catalysts could be separated after a simple work-up and reused for several times.     

Water as an Efficient Solvent for Oxygenation Transformations with 34% Hydrogen Peroxide Catalyzed by some Heteropolyoxometalates

Summary. A highly efficient, selective, fast, and cheap protocol is developed for oxidation of aromatic amines and alcohols utilizing 34% hydrogen peroxide in water catalyzed by some W- and Mo-based heteropolyoxometalates. Findings showed that dodecatungstophosphoric acid, H₃PW₁₂O₄₀, was the most efficient catalyst in the examined oxidation reactions. This methodology may prove to be a valuable alternative for eco-friendly green oxidation. Inherent simplicity, easy work up, and using regenerable catalysts were other key aspects of this oxidation protocol.     

1H NMR Study of Hindered Internal Rotation of Tetramethylthiuram Disulfide in Binary Dimethyl Sulfoxide‐Chloroform Mixtures

Hindered internal rotation about the C‐N single bonds joining the thiuram disulfide was studied by ¹H NMR complete line‐shaped analysis in different dimethyl sulfoxide‐chloroform (DMSO‐CDCl₃) mixtures. From the temperature dependence of methyls proton spectra, activation parameters (E_a, ΔH^≠, ΔS^≠, and ΔG^≠) were obtained. The Arrhenius plots showed a distinct isokinetic temperature at about 35 °C at which the exchange rate is more or less independent of the solvent composition. The resulting ΔH^≠ against TΔS^≠ plot showed a firmly good linear correlation, indicating the existence of an enthalpy‐entropy composition in an exchange process.     

Identification and characterization of fenton oxidation products of surfactants by electrospray mass spectrometry and by solid phase microextraction gas chromatography mass spectrometry. 2. Fatty alcohol polyethoxy sulphates

The Fenton reaction for the degradation of surfactants has been investigated and partial degradation products have been identified and characterized by mass spectrometry for the case of fatty alcohol polyethoxy sulphates. The polar water-soluble products were investigated by liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization (ESI), and the volatile products leaving the mixture during the reaction were trapped by means of solid phase microextraction (SPME) and investigated by gas chromatography/mass spectrometry (GC/MS) with electron and chemical ionization. The oxidation leads to the formation of products with hydroxyl and epoxide groups due to insertion of oxygen atoms or with terminal ethoxylic moieties deriving from the loss of the hydrophilic sulphate group. The formation of volatile aldehydes is also observed, corresponding to the fragmentation between hydrocarbon and ethoxylic chains. The extent of mineralization is dependent on peroxide and iron(II) concentrations. Copyright 2000 John Wiley & Sons, Ltd.     

A new method for the synthesis of functionalized maleimides

An effective route to novel maleimides is described, which involves the reaction of an enamine derived from the addition of a secondary amine to a dialkyl acetylenedicarboxylate with an arylsulfonyl isocyanate. These maleimides in solution indicate dynamic NMR because of restricted rotation around the carbon-nitrogen bond, resulting from conjugation of the side-chain nitrogen with the adjacent α,β-unsaturated ester group.