Complexation of metal ions with the novel diazadithia crown ether carrying two anthryl pendants in acetonitrile–tetrahydrofuran

A new crown ether carrying two anthryl groups with nitrogen–sulfur donor atom was designed and synthesized by the reaction of the corresponding macrocyclic compound and 9-chloromethyl anthracene. The influence of metal cations such as Al³⁺, Zn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ on the spectroscopic properties of the ligand was investigated in acetonitrile–tetrahydofuran solution (1/1) by means of absorption and emission spectrometry. Absorption spectra show isosbestic points in the spectrophotometric titration of Fe²⁺, Fe³⁺, Al³⁺, Cu²⁺ and Hg²⁺. The results of spectrophotometric titration experiments disclosed the complexation stoichiometry and complex stability constant of the novel ligand with Fe²⁺, Fe³⁺, Al³⁺, Cu²⁺and Hg²⁺cations. The presence of excess amounts of Al³⁺, Zn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺, Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ cations caused an enhancement of anthryl fluorescence. The ligand showed good sensitivity for Zn²⁺ with respect to other metal cations with linear range and detection limit of 1.4 × 10^?7 to 4.1 × 10^?6 M and 1.0 × 10^?8 M respectively.     

A stability indicating assay method for cefuroxime axetil and its application to analysis of tablets exposed to accelerated stability test conditions

Cefuroxime axetil is the esterified form of cefuroxime, injectable second generation cephalosporine antibiotic that can be given orally. Stereo and structural isomers of cefuroxime axetil (CA), anti-cefuroxime axetil (ACA) and Delta(3)-cefuroxime axetil (DCA), can be present in cefuroxime dosage forms as the process related impurities as well as possible degradation product. Sensitive and precise reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for the determination of cefuroxime axetil in the presence of its degradation products in solid dosage forms. The RSD values for cefuroxime axetil, anti-cefuroxime axetil and Delta(3)-cefuroxime axetil of 1.80, 1.99 and 2.48%, respectively, indicated a good precision of the RP-HPLC method. Developed RP-HPLC method was sensitive with LOD = 0.08 microg mL(-1) and LOQ = 0.60 microg mL(-1) for anti-cefuroxime axetil and LOD = 0.06 microg mL(-1) and LOQ = 0.45 microg mL(-1) for Delta(3)-cefuroxime axetil. Holding studies were carried out on Ceroxim tablets, according to ICH regulation at 30 degrees C/60% relative humidity (RH) and 40 degrees C/75% RH for 1, 2, 3 and 6 months. The review data from the stability studies conducted, show the significant content change of Delta(3)-cefuroxime axetil.     

Oxidation of azides by the HOF.CH3CN: a novel synthesis of nitro compounds

The HOF.CH3CN complex, readily prepared by passing F2 through aqueous acetonitrile, is an exceptionally efficient oxygen transfer agent. It is unique in its capacity to oxidize various azides into the corresponding nitro derivatives. This method requires short reactions times and room temperature or below, and the desired nitro compounds were usually isolated in very good yields. The respective nitroso derivatives are believed to be the intermediates in this reaction. Functional groups such as aromatic rings, ketones, nitriles, halides, alcohols, and esters are tolerated. Sulfides react with HOF.CH3CN usually at the same rate as azides. Amines and olefins, however, react faster, so they have to be protected first. Nitro derivatives with various oxygen isotopes can be made using the labeled H18OF.CH3CN. In the case of chiral azides the stereochemistry around the nitrogen-bonded carbons is retained.     

Trace analysis of antidepressants in environmental waters by molecularly imprinted polymer-based solid-phase extraction followed by ultra-performance liquid chromatography coupled to triple quadrupole mass spectrometry

This paper presents the development, optimization, and validation of an innovative method to analyze trace concentrations of seven selected psychoactive pharmaceuticals in environmental waters. Hereby, the solid-phase extraction (SPE) potential of molecularly imprinted polymers (MIPs) in terms of extraction recovery, breakthrough, precision, and selectivity is studied for the first time. Instrumental analysis by ultra-performance liquid chromatography coupled to triple quadrupole mass spectrometry allowed a rapid (run time = 7.5 min) and sensitive (instrumental detection limit ≤7 pg injected) quantification of the target analytes. A systematic optimization study revealed that, among the seven compounds of interest, mainly the selective serotonin reuptake inhibitors paroxetine, fluoxetine, and citalopram are selectively retained on the MIPs. Experiments performed in spiked river water, sewage treatment plant (STP) effluent and influent showed for these compounds extraction recoveries higher than 70%, breakthrough volumes up to 200 mL, method detection limits (MDL) as low as 0.5 ng/L, and good precision (exemplified by relative standard deviations better than 15%, n ≥ 3). Compared to the widely used hydrophilic–lipophilic balanced (HLB) polymers, the newly developed MIPs indicated to be more resistant toward matrix effects induced ion signal suppression particularly when dealing with relative dirty samples like STP influents. As a result of the better selectivity, the MDL obtained with the MIP-based SPE method was up to a factor of 7 lower compared to those obtained with a recently reported multi-residue HLB method. However, optimizing a HLB method in terms of selectivity, e.g., by introducing a stronger washing protocol, can significantly reduce its MDL up to values approximating those obtained with MIPs.     

Recent trends in the liquid chromatography–mass spectrometry analysis of organic contaminants in environmental samples

An overview of liquid chromatography–mass spectrometry methods used for the determination of trace organic contaminants in environmental samples is presented. Among the organic contaminants the focus is given on five groups of emerging contaminants that raised most concern as environmental contaminants and therefore attracted attention of a research community: pharmaceuticals, drugs of abuse, polar pesticides, perfluorinated compounds and nanoparticles. Various aspects of current LC–MS methodology, using tandem and hybrid MS instruments, including sample preparation, are discussed.     

Real quadratic flexible division algebras

In this paper we give a new process called vectorial isotopy, in order to classify the eight-dimensional real quadratic flexible division algebras, and we solve the isomorphism problem.     

Cruciform pi-systems: hybrid phenylene-ethynylene/phenylene-vinylene oligomers

The cruciform pentamers 3a-g were synthesized by a combined Horner-Sonogashira approach; their band gaps vary significantly with emission varying from blue to red depending upon their substituent pattern.     

Separation and fluorodensitometric determination of some purine derivative drugs by thin-layer chromatography on starch and cellulose

Summary Purine derivative drugs, aminophylline, theophylline, xantinolnicotinate, 6-mercaptopurine, 6-thyoguanine, azathioprine, 1-methylxantine, 3-methylxantine, 1-methyluric acid, 1,3-dimethyluric acid, 6-thioxantine, 2-amino-6-methylmercaptopurine, were separated by thin-layer chromatography on rice starch and cellulose by three different solvent systems. Conditions for quantitative fluorodensitometric determination of purine derivatives drugs were investigated.     

Absolute transition probabilities from the 53.2 keV level in105Ag

The halflife of the 9/2 ₁ ⁺ , 53.2 keV state in¹⁰⁵Ag has been measured by the delayed-coincidences technique to 2.33±0.08 ns. The reduced transition probabilities between the 9/2 ₁ ⁺ and 7/2 ₁ ⁺ states have been deduced and compared with the theoretical predictions within the cluster-vibration coupling model (Alaga model).