Determination of MTBE in drinking water using corona discharge ion mobility spectrometry

Methyl tertiary-butyl ether (MTBE) is an organic compound which is used as a gasoline additive. Contamination of ground and surface water can occur due to large scale use of MTBE and its high solubility in water. According to United State Environmental Protection Agency (USEPA), MTBE is a possible human carcinogen at high doses and its detection and measurement in the water is important as concerned about human health. In this work, ion mobility spectrometry (IMS) equipped with a corona discharge ionization source was used for determination of MTBE in drinking water. Both pure and aqueous solutions of MTBE were studied and their ion mobility spectra were obtained at different temperatures. Using a calibration curve for detection of MTBE in drinking water, a detection limit (LOD) of 1 mg/L was obtained by IMS. This work proved that, IMS with corona discharge can be used for fast and direct detection of MTBE in water sample without any sample preparation.     

Amino acid ionic liquid‐based titanomagnetite nanoparticles: An efficient and green nanocatalyst for the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazoles

The amino acid ionic liquid tetrabutylammonium asparaginate (TBAAsp) was immobilized on titanomagnetite (Fe_3?xTi_xO₄) nanoparticles in a facile one‐pot process using an organosilane compound (TMSP) as spacer. The modified Fe_3?xTi_xO₄@TMSP@TBAAsp magnetic nanoparticles were characterized using Fourier transform spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry and thermogravimetric analysis. The resulting analytical data clearly verified the successful immobilization of the ionic liquid on the magnetic substrate. The magnetic ionic liquid‐based nanoparticles exhibited high catalytic activity in the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazole derivatives via a one‐pot three‐component reaction under mild reaction conditions. The catalyst was easily recycled and reused for at least six runs without any considerable loss of activity.     

Positive polynomials on projective limits of real algebraic varieties

We reveal some important geometric aspects related to non-convex optimization of sparse polynomials. The main result, a Positivstellensatz on the fibre product of real algebraic affine varieties, is iterated to a comprehensive class of projective limits of such varieties. This framework includes as necessary ingredients recent works on the multivariate moment problem, disintegration and projective limits of probability measures and basic techniques of the theory of locally convex vector spaces. A variety of applications illustrate the versatility of this novel geometric approach to polynomial optimization.     

A family of $$ 2^{\aleph _1 } $$ logarithmic functions of distinct growth rates

We construct a totally ordered set Γ of positive infinite germs (i.e. germs of positive real-valued functions that tend to +∞), with order type being the lexicographic product ℵ₁ × ℤ². We show that Γ admits $ 2^{\aleph _1 } $ 2^{\aleph _1 } order preserving automorphisms of pairwise distinct growth rates.     

Liquid crystalline G phase of self assembled donor-acceptor molecules by intermolecular hydrogen bonding

The interaction with donor p-n-alkylbenzoic acid and acceptor nonyl-p-hydroxy benzoate molecules was studied. The likely association of these molecules to complexes is studied by intermolecular hydrogen bonding. The textures are observed by polarizing optical microscope with corresponding transitions confirmed by differential scanning calorimetry. The molecular complexes exhibited enantiotropic crystal G phases in both heating and cooling cycles. The relevant functional groups C═O, C-O and OH in formation of molecular complexes are attributed with spectral shifts in infrared spectra and further with absorption studies. The proton NMR studies convinced the structural aspects of hydrogen bonded structure. Crystal parameters were studied with powdered X-ray diffraction. The results show that constituent molecules self organize through intermolecular hydrogen bonding in the formation of crystal G phase.     

Optimization of photo-polymerized sol–gel monolithic stationary phases prepared in polyacrylate-coated fused-silica capillaries for capillary electrochromatography

The preparation of photo-polymerized sol–gel monolithic stationary phases (MSP) within 100 μm internal diameter polyacrylate-coated fused-silica capillaries for use in capillary electrochromatography (CEC) was optimized. Eight mixtures containing different amounts of methacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid solution as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photo-initiator were irradiated at 370 nm inside the capillaries in order to complete the MSP polymerization, according to a fractional factorial experimental design 2_IV^4-1. All the preparation procedure, from capillary pretreatment until the MSP is ready to use in CEC, were made in less than four hours in mild conditions. A high pressurization injection device (HPID) useful for micro-volume syringes was built in order to achieve practical, controlled and precise injections of sols, solvents and electrolytes in the capillaries. The eight MSP were equally washed, conditioned and submitted to CEC procedures via short-end injection, which showed higher efficiency and peak height taking shorter analysis time. Electrochromatographic behaviors of the MSP were corroborated with morphological characterizations by scanning electron microscopy. The optimum condition, which allowed the separation of standard mixture containing thiourea (marker compound), naphthalene, acenaphthene, fluorene, phenanthrene and anthracene in twelve minutes without external pressure assistance, showed efficiencies up to 51,460 N/m, relative standard deviation from 0.05 to 3.3% for migration/retention time and from 0.14 to 1.6% for relative area (considering thiourea as an internal standard) and also showed no statistical evidence that three MSP prepared at the same condition are different within 95% confidence interval.     

Preparation of micron-sized, monodisperse polymeric nonspherical particles with tunable shapes by micromolding–polymerization

In this work, we present a novel synthesis method for the preparation of micron-sized, monodisperse polymeric nonspherical particles without changing the shape of a precursor. In this technique, which we called micromolding–polymerization, nonspherical particles of second polymer were formed directly on the surface of micromolds (solvent-swollen polymeric particles). The experimental results showed that the affinity between the second polymer and micromolds, and size and concentration of the oligoradicals specify the shape of the particles.     

Preparation of zinc sodium polyphosphates glasses from coacervates precursors. Characterisation of the obtained glasses, and their applications

A soft chemistry route is described to obtain glasses in the P₂O₅–Na₂O–ZnO–H₂O. It is based on the addition of zinc salts to coacervates prepared from sodium polyphosphate. The processing of these coacervates leads to polyphosphate glasses with the same properties as those of glasses prepared in the classical way. So far, little work has been implemented in this system using ‘coacervate route’. However, it makes an attractive method for coating and joining processes on the industrial scale. As the anion associated to zinc may take part in the adhesion mechanism, coacervate formation has been studied using zinc chloride, nitrate and sulphate as starting materials. The physical properties of the glasses obtained by this method are reported and potential applications of zinc and silver coacervate are described.     

Experimental and numerical analysis of automotive gearbox rattle noise

The aim of this work is to characterize the rattle noise of automotive gearboxes, resulting from impacts between toothed wheels of unselected gear ratios. These stereo-mechanical impacts are modeled by a coefficient of restitution which describes damping during the squeezing of the lubricant film for approaching surfaces, and the elastic deformation of impacting bodies. The dynamic response of the loose gear first depends on the design parameters and the engine operating conditions. The unknown parameters are the drag torque and the coefficient of restitution. They are identified experimentally through implementation of two optical encoders in an actual automotive gearbox and the operation of a specific test bench which replicates the automotive power train. Models of the different drag torque sources are validated from analysis of the free damped response of the driveline. The coefficient of restitution and its probability density function are measured from experiments under stationary operating conditions. A nonlinear model is built. The dynamic response of the loose gear depends on the dimensionless backlash, the coefficient of restitution and a dimensionless parameter proposed to describe the rattle excitation level. Experiments under controlled excitation are performed to validate the assumptions, to confirm the ability of the parameter proposed to describe the rattle noise threshold, and to characterize the dynamic response. The nonlinear model predictions are fitted with the drag torque and coefficient of restitution previously identified. They are compared with measurements to demonstrate the ability of the model to predict gear rattle for any loose gear, any gearbox and any operating condition.