Molecularly-imprinted polypyrrole-modified stainless steel frits for selective solid phase preconcentration of ochratoxin A

A molecularly-imprinted polymer (MIP) was prepared by electropolymerization of pyrrole (Py) onto a stainless steel frit, using ochratoxin A (OTA) as the template, in order to make a micro solid phase preconcentration (SPP) device. The OTA template was removed with 1% triethylamine (TEA) in methanol. Compared to non-imprinted polypyrrole (PPy), the molecularly-imprinted polypyrrole (MIPPy) enhanced the selective binding of OTA. The percentage recovery improved from 0 to 40% when the OTA sample solution was acidified with 1 M HCl (1% by volume). At a flow rate of 0.2 mL/min, maximum OTA binding was reached in 6 min after a total loading of 3.2 ng OTA. Final elution of the OTA was analyzed by high performance liquid chromatography (HPLC) with fluorescence detection, using 20:80 v/v acetonitrile–ammonia buffer (NH₄Cl/NH₃, 20 mM, pH 9.2) as the mobile phase. The MIPPy-SPP-HPLC results clearly demonstrated that the MIPPy-SPP device afforded selective preconcentration of OTA from red wine samples, at OTA concentration levels as low as 0.05 ppb, prior to HPLC analysis.     

Cyclization of Nitrospirobenzopyrans to Bridged Benzoxazepino[3,2-a]indoles

Condensation of 1-substituted 1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-ones with 5-nitrosalicylaldehyde afforded 1′-[(N-monosubstituted carbamoyl)methyl]indoline nitrospirobenzopyrans. Treatment of the latter with strong base led to the formation of a mixture of cis/trans-5a,13-methano-1,3-benzoxazepino[3,2-a]indoles. Results of semiempirical calculations gave evidence that such a transformation of nitrospirobenzopyrans to bicyclic indole derivatives could proceed via a single transition state, where the negatively charged carbon atom attacks the vinylic double bond of the spiropyran system.     

Microemulsion photopolymerization of methacrylates stabilized with sodium dodecyl sulfate and poly(N-acetylethylenimine) macromonomers

Methyl methacrylate and butyl methacrylate were polymerized in oil-in-water microemulsions that were stabilized by sodium dodecyl sulphate (SDS). A poly(N-acetylethylenimine) (PNAEI) macromer was also included in the recipe, as a cosurfactant and a comonomer. Polymerizations were initiated by UV-irradiation. The average diameters of latex particles, obtained by STM, were in the range of 17-200 nm. The experimental data evidenced that the particle size was mainly dependent on the SDS/PNAEI ratio. Polymerization yields were around 75-85%. The synthesized copolymers have viscosity average molecular weights in the range of 2.1-2.4×10⁶ and glass transition temperatures of 38.0-43.5°C, lower than those obtained without using PNAEI. The investigation by means of FTIR and 1H-NMR techniques revealed that PNAEI was incorporated into the nanoparticles.     

Hydrophilic Treatment of the Dyed Nylon-6 Fabric using High-density and Extensible Antenna-coupling Microwave Plasma System

High density and well surface-distributed oxygen microwave plasma with an extensible antenna-coupling design was utilized to modify a densely weaved and large-surface-area Nylon-6 fabric within a short treatment time. Plasma pretreatment and subsequent acrylic acid (AAc) or 2-hydroxyethyl methacrylate (HEMA) grafting process were studied and optimized at the stage after dyed and finished procedure. The monomer-grafted dyed Nylon-6 fabrics evolved lasting hydrophilic properties and thereafter created or improved surface properties such as water diffusion, drainage, moisture regain and water absorbency, in different degrees. The pHEMA-grafted sample exhibited minor effect in color perception, which was also much hydrophilic than the pAAc-grafted one. Based upon surface analyses and wetting assessment, the penetration of HEMA monomer into the plasma-treated fabric matrix contributed to the facilitation of wetting properties. This work accordingly ensures such plasma-induced system to incorporate with the pattern of hydrophilic properties on the analogous textiles without interrupting their finishing process.     

On the modelling of solid state reactions.Synthesis of YAG

There is a model of yttrium aluminium garnet (YAG) synthesis presented in this article. The developed model is based on nonlinear reaction–diffusion partial differential equations. The solution was carried out numerically using finite difference techniques. We got dependability curves for diffusion and reaction rates and offered possible method to localize values of diffusion and reaction rate constants precisely enough.AMS subject classification: 35K57, 65M06     

Phase Equilibria in the Ni–Al–W System at 900°C

Multicomponent Ni-base alloys exhibit good mechanical properties even at elevated temperatures and they are widely used for industrial production of exertion-resistive parts of engines. These properties are mainly determined by the coexistence of a disordered γ matrix with a face centred cubic lattice and cuboidal domains of its ordered γ′ structure. Therefore it is useful to study phase equilibria in Ni-base systems, namely in the regions involving both mentioned phases. One of the conclusions of our recent work on Ni–Al–Cr–W system was a necessity of modification of selected thermodynamic parameters of the ternary Ni–Al–W subsystem in order to achieve a better agreement of our experimental observations with theoretical modelling. This involves new measurements of the microstructure of selected samples of the Ni–Al–W system at 900°C and the comparison of the results with existing literature data in order to confirm our conclusions on higher order system investigated before. It is a first step on the way to an assessment of the Ni–Al–W system, which has not been done before.     

Highly accurate gas chromatographic analysis of reference gases for use in vehicle emission measurements

 A highly accurate gas chromatographic analytical method has been developed for the determination of the composition of gas mixtures. It was tested using a reference gas as an example consisting of 3.5% of CO, 14% of CO₂, 0.2% of propane and residual N₂ intended for the use in vehicle emission measurements. The method is based on comparison measurements with samples of a calibration gas, whose composition is iteratively adapted to that of the sample investigated using a gravimetric gas mixing method. For the gas chromatographic measurement, a molecular sieve column and a polymer column are used in parallel and in isothermal operation. All gas components can be determined by a single gas chromatographic measurement, and the relative uncertainty of measurement achievable is ?0.4%. Received: 6 March 1996/Revised: 30 May 1996/Accepted: 6 June 1996     

Direct qualitative analysis of triacylglycerols by electrospray mass spectrometry using a linear ion trap

Triacylglycerols (TAGs) isolated from a biological sample provide a challenge for mass spectrometric analysis because of the complexity of naturally occurring TAGs, which may contain different fatty acyl substituents resulting in a large number of molecular species having the identical elemental composition. We have investigated the use of mass spectrometry to obtain unambiguous information as to the individual TAG molecular species present in a complex mixture of triacylglycerols using a linear ion trap mass spectrometer. Ammonium adducts of TAGs, [M+NH4]+, were generated by electrospray ionization, which permitted the molecular weight of each TAG molecular species to be determined. The mechanisms involved in the decomposition of the [M+NH4]+ and subsequent fragment ions were investigated using deuterium labeling, MS/MS, and MS3 experiments. Collision induced decomposition of [M+NH4]+ ions resulted in the neutral loss of NH3 and an acyl side-chain (as a carboxylic acid) to generate a diacyl product ion. MS/MS data were used to identify each acyl group present for a given [M+NH4]+ ion, and this information could be combined with molecular weight data to identify possible TAG molecular species present in a biological extract. Subsequent MS3 experiments on the resultant diacyl product ions, which gave rise to acylium (RCO+) and related ions, enabled unambiguous TAG molecular assignments. These strategies of MS, MS/MS, and MS3 experiments were applied to identify components within a complex mixture of neutral lipids extracted from RAW 264.7 cells.     

Behavior of rifampicin in association with<Emphasis Type="Italic"> β</Emphasis>-cyclodextrin in aqueous media: a spectroscopic and conductometric study

The behavior of rifampicin (D) with -cyclodextrin (-CyD) in aqueous media (W) has been examined by means of UV-vis spectroscopy and conductivity measurements over the temperature range 15–30 °C. The UV-vis study has been used to characterize the systems. The estimated molar absorption coefficient for D/CyD/W system was 10757±280 M^–1 cm^–1 in comparison to the value of 6133±99 M^–1 cm^–1 for D/W system. The conductivity was measured (i) as a function of [D] for binary D/W systems, (ii) as a function of [CyD], keeping the concentration of drug constant, for D/CyD/W system, and (iii) as a function of [D] in the presence of a constant cyclodextrin concentration. Two transition points were observed for D/CyD/W system at constant [CyD], which were assigned as cac-1 and cac-2. The stoichiometry of the association was estimated from the conductivity data. This was obtained from [drug] value at which the change in slope of occurs. The standard free energy change, of aggregation was also calculated from the critical concentration data. An attempt has also been made to estimate the stoichiometry of -cyclodextrin:rifampicin association.