Determination of phthalate esters in bottled water using dispersive liquid–liquid microextraction coupled with GC–MS

Dispersive liquid–liquid microextraction method was developed for the determination of the amount of phthalate esters in bottled drinking water samples and dispersive liquid–liquid microextraction samples were analyzed by GC–MS. Various experimental conditions influencing the extraction were optimized. Under the optimized conditions, very good linearity was observed for all analytes in a range between 0.05 and 150 μg/L with coefficient of determination (R²) between 0.995 and 0.999. The LODs based on S/N = 3 were 0.005–0.22 μg/L. The reproducibility of dispersive liquid–liquid microextraction was evaluated. The RSDs were 1.3–5.2% (n = 3). The concentrations of phthalates were determined in bottled samples available in half shell. To understand the leaching profile of these phthalates from bottled water, bottles were exposed to direct sunlight during summer (temperature from 34–57°C) and sampled at different intervals. Result showed that the proposed dispersive liquid–liquid microextraction is suitable for rapid determination of phthalates in bottled water and di‐n‐butyl, butyl benzyl, and bis‐2‐ethylhexyl phthalate compounds leaching from bottles up to 36 h. Thereafter, degradation of phthalates was observed.     

Simplified Approach to the Uncatalyzed Knoevenagel Condensation and Michael Addition Reactions in Water using Microwave Irradiation

Use of microwave irradiation in the synthesis of arylidenemalononitrile and benzopyran derivatives in water without catalyst is a clean method with high yield.     

Synthesis of Diaryl Ethers Through the Copper-Catalyzed Arylation of Phenols with Aryl Iodides Using KF/Al2O3

An efficient synthesis of diaryl ethers by the copper-catalyzed arylation of phenols with a variety of aryl iodide susing KF/Al₂O₃ as a suitable base and CuI and 1,3 diphenyl-1,3 propandione as the catalyst is described.     

Stereoselective total synthesis of (−)-brevisamide

The stereoselective total synthesis of (−)-brevisamide, a novel marine cyclic ether alkaloid isolated from dinoflagellate karenia brevis is described. The key steps involved in this synthesis are the Sharpless asymmetric epoxidation and regioselective ring opening of chiral epoxide by Gilman's reagent. The tetrahydropyran core has been constructed by an intramolecular S_N2 cyclisation.     

Water Structure Modification by Sugars and Its Consequence on Micellization Behavior of Cetyltrimethylammonium Bromide in Aqueous Solution

Water structure modification by sugars with a wide difference in stereoregular structures ranging from monosaccharide to trisaccharide and its consequence on the micellization behavior of cetyltrimethylammonium bromide (CTAB) in aqueous medium have been investigated. The characteristic variation in water absorption peaks in the presence of d(?)fructose has been studied by near-infrared spectroscopy. The analyses show that the hydrogen bonding capability of d(+)glucose, d(?)fructose, sucrose, trehalose and raffinose is mainly responsible for the variation in water-additive interactions. The critical micelle concentration determined by specific conductivity measurement and aggregation number determined by steady state fluorescence quenching method show significant variations in presence of additives for CTAB in aqueous solution. The sugars interact with the water structure to varying extents owing to differences in hydrogen bonding capability depending on the stereoregularity of the structure. This induces differences in the microenvironment for competition between the hydrophobic interaction and degree of hydration of the hydrophilic group of the surfactant to ultimately influence the micellization behavior in aqueous solution.     

Study of Sorption of 2,4‐D on Outer Peristaltic Part of Waste Tire Rubber Granules

From this study it was evident that outer peristaltic parts of waste tire granules gave the highest removal. Film and pore diffusions are the major factors controlling rates of sorption from solution by porous adsorbents. For sorption of 2,4‐D on waste tire rubber granules, the sorption rate coefficient of second‐order kinetic equation was utilized indirectly to determine the rate‐limiting step. The diffusion coefficient lies in the scale of 10^?8 cm²/s, and the pore diffusion coefficient is in the range of 10^?9–10^?10 cm²/s. So both film and pore diffusion are rate limiting. Considering external mass transfer from fluid to particle, using the effect of initial concentration, and using the effect of adsorbent size, no conclusion was reached regarding rate‐controlling steps. It is apparent from the study that external mass transfer (film diffusion) as well as intra‐particle diffusion (pore diffusion) play significant roles in the sorption process for 2,4‐D removal from water onto rubber granules.     

Effect of adenine on bacterial translocation using technetium-99m labeled E. coli in an intestinal obstruction model in rats

This study aims to investigate effects of adenine on bacterial translocation (BT) using ^99mTc-labeled E. coli in an intestinal obstruction rat model. In the study twenty-one rats were used. The rats were divided into three groups according to different feeding patterns. The control group (CG) was fed with a standard chow diet for 7 days. Group A1 and group A2 were fed with adenine supplemented chow diet for 7 days. At the end of the feeding period, after all groups was submitted intestinal obstruction. ^99mTc-E. coli was injected into the rats’ terminal ileum under anesthetic. The rats were sacrificed under aseptic conditions at 24th h after the surgery. The uptake of ^99mTc-E. coli was determined in organs such as the liver, mesenteric lymph nodes, spleen and ileum. Group A1 and group A2 results show that the uptake of ^99mTc-E. coli decreased in the blood and organs comparing to the CG. As a result, it was observed that adenine reduced the level of BT when compared with CG. The beneficial effect of adenine on BT in intestinal obstruction was observed. However, further studies are needed to more clearly assess how this benefit can be achieved.     

Liquid crystalline banana‐shaped monomers derived from 2,7‐naphthalene: synthesis and properties

Three banana‐shaped monomers, i.e. 2,7‐naphthalene bis[4‐(4‐allyloxyphenylazo)‐benzoate], 2,7‐naphthalene bis[4‐(4‐allyloxy‐3‐fluorophenylazo)benzoate] and 2,7‐naphthalene bis{4‐[4‐(10‐undecenyloxy)phenylazo]benzoate}, containing azobenzene as side arms, 2,7‐dihydroxynaphthalene as central units and terminal double bonds as polymerisable functional groups, were synthesised and their mesophase behaviour investigated. Polarizing optical microscopy and DSC measurements reveal that all compounds exhibit nematic mesophases. The absorption spectrum of the trans‐azobenzene groups displays a high‐intensity π–π* transition at about 365 nm and a low‐intensity n–π* transition at around 450 nm for all compounds. Hence, photochromism can be achieved by the introduction of the azo linkage to banana‐shaped liquid crystals molecules.     

Anomalous behaviour in the SmA*–SmCA* pre‐transitional regime of a chiral swallow‐tailed antiferroelectric liquid crystal

The temperature‐ and electric field‐dependent dielectric relaxation and polarisation of a new chiral swallow tailed antiferroelectric liquid crystal, i.e. 1‐ethylpropyl (S)‐2‐{6‐[4‐(4′‐decyloxyphenyl)benzoyloxy]‐2‐naphthyl}propionate (abbreviated as EP10PBNP), were investigated. The electric field‐induced dielectric loss spectra of EP10PBNP revealed electroclinic and anomalous dielectric behaviour in the chiral smectic A (SmA*)–chiral antiferroelectric smectic C (SmC_A*) pre‐transitional regime. From an analysis of thermal hysteresis of the dielectric constant, electric field‐induced polarisation and dielectric loss spectra, the appearance of a ferrielectric‐like mesophase is observed followed by an unstable SmC_A* phase in the SmA*–SmC_A* pre‐transitional regime.