Stereoregulation in cationic polymerization by designed Lewis acids. II. Effects of alkyl vinyl ether structure

Stereoregulation in the cationic polymerization of various alkyl vinyl ethers was investigated with bis[(2,6‐diisopropyl)phenoxy]titanium dichloride ( 1 ; catalyst) in conjunction with the HCl adduct of isobutyl vinyl ether as an initiator in n‐hexane at −78 °C. The tacticities depended on the substituents of the monomers. Isobutyl and isopropyl vinyl ethers gave highly isotactic polymers (mm = 83%), whereas tert‐butyl and n‐butyl vinyl ethers resulted in lower isotactic contents (mm ∼ 50%) similar to those for TiCl₄, a conventional Lewis acid, thus indicating that the steric bulkiness of the substituents was not the critical factor in stereoregulation. A statistical analysis revealed that the high isospecificity was achieved not by the chain end but by the catalyst 1 or the counteranion derived therefrom. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1060–1066, 2001     

Summary of ISO/TC 201 Standard: ISO 29081: 2010, surface chemical analysis—Auger electron spectroscopy—reporting of methods used for charge control and charge correction

This international standard specifies the minimum amount of information required for describing the methods of charge control and charge correction in measurements of Auger electron transitions from insulating specimens by electron‐stimulated AES to be reported with the analytical results. Information is provided in an Annex on methods that have been found useful for charge control prior to or during AES analysis. The Annex also includes a summary table of methods or approaches, ordered by simplicity of approach. A similar international standard has been published for XPS (ISO 19318: 2003(E), Surface chemical analysis—XPS—reporting of methods used for charge control and charge correction. Copyright © 2010 John Wiley & Sons, Ltd.     

Simultaneous separation and rapid determination of spironolactone and its metabolite canrenone in different pharmaceutical formulations and urinary matrices by capillary zone electrophoresis

The aim of this study was to develop a novel, sensitive, precise, simple, and rapid capillary zone electrophoresis method for the quality control of spironolactone in three different formulation types and a rapid simultaneous determination of the content of spironolactone and canrenone in urine samples using fluocinonide as an internal standard. After optimization of separation conditions, the electrolyte solution was the pH 5.5, 20 mM phosphate buffer containing 4.5 g/L sulfated‐β‐cyclodextrin, 15 kV of electric filed across the capillary applied at 25°C. A diode array detector was used, and the detection wavelength was 260 nm. Under optimum conditions, good linearity was achieved with correlation coefficients from 0.9976 to 0.9997. Detection limits were 0.56 and 0.20 μg/mL, and the quantitation limits were 1.87 and 0.67 μg/mL, respectively. Excellent accuracy and precision were obtained. Recoveries of the analytes varied from 100.8 to 103.1%. The results indicated that baseline separation of analytes was obtained and this method was suitable for quantitative determination of spironolactone in pharmaceutical preparations and rapid simultaneous determination of the content of spironolactone and its major metabolite canrenone in urine samples.     

Controllable synthesis of titania/reduced graphite oxide nanocomposites with various titania phase compositions and their photocatalytic performance

A facile method is presented for preparing TiO2 /reduced graphite oxide(RGO) nanocomposites with phase-controlled TiO2 nanoparticles via redox reaction between the reductive titanium(Ⅲ) precursor and graphite oxide(GO),and a series of TiO2 /RGO composites with various TiO2 phase compositions were obtained.In all the titania/RGO composites,the TiO2 nanoparticles were uniformly distributed on the surface of the RGO.The TiO2 consisted of anatase phase particles in the form of square-plates with edges less than 10 nm and the rutile phase nanorods in diameters less than 10 nm.The performances of the as-prepared TiO2 /RGO composites were investigated on catalytically degrading phenol under visible light irradiation.The TiO2 /RGO composites can effectively degrade phenol under visible light irradiation,and the phase composition of TiO2 in the composites significantly influences the activities of these catalysts.     

The potential of Raman spectroscopy for characterisation of the fatty acid unsaturation of salmon

Raman spectroscopy has been evaluated for characterisation of the degree of fatty acid unsaturation (iodine value) of salmon (Salmo salar). The Norwegian Quality Cuts from 50 salmon samples were obtained, and the samples provided an iodine value range of 147.8-170.0 g I₂/100 g fat, reflecting a normal variation of farmed salmon. Raman measurements were performed both on different spots of the intact salmon muscle, on ground salmon samples as well as on oil extracts, and partial least squares regression (PLSR) was utilised for calibration. The oil spectra provided better iodine value predictions than the other data sets, and a correlation coefficient of 0.87 with a root mean square error of cross-validation of 2.5 g I₂/100 g fat was achieved using only one PLSR component. The ground samples provided comparable results, but at least two PLSR components were needed. Higher prediction errors were obtained from Raman spectra of intact salmon muscle, and this may partly be explained by sampling uncertainties in the relation between Raman measurements and reference analysis. All PLSR models obtained were based on chemically sound regression coefficients, and thus information regarding fatty acid unsaturation is readily available from Raman spectra even in systems with high contents of protein and water. The accuracy, the robustness and the low complexity of the PLSR models obtained suggest Raman spectroscopy as a promising method for rapid in-process control of the degree of unsaturation in salmon samples.     

Gas-phase behaviour of negative ions produced from thiazidic diuretics under electrospray conditions

A systematic mass spectrometric study of 10 thiazidic diuretics and related compounds was undertaken by mass spectrometry (MS) with electrospray ionization in the negative ion mode. Collisional dissociation 'in-source' (CID-MS) and in a low-pressure collision cell (CID-MS/MS) were compared in both excitation regions. Spectra obtained by CID-MS and by CID-MS/MS were matched. Using the two methods, loss of HCl and consecutive dissociations from 2HCl losses were exhibited from compounds such as methyclothiazide and trichlormethiazide but not from other thiazidic diuretics that contain chlorine substituents in the aromatic moiety. However, deprotonated dichlorphenamide gave rise to loss of HCl by CID-MS and CID-MS/MS. For other diuretics such as hydroflumethiazide and hydrochlorothiazide, the loss of HCN and [HCN + SO(2)] was relevant. Reaction mechanisms were checked by means of deuterium-hydrogen exchange, which showed that deprotonation took place regioselectively on the heterocyclic moiety. The cleavage pathways require molecular isomerization forming ion-dipole complexes prior to decompositions, allowing long-distance proton transfer for neutral elimination. Identifications of the most specific fragmentations presented in this paper were applied to the screening and unambiguous identification of diuretics for horse doping control.     

Temperature program optimization by computer simulation for the capillary GC analysis of fatty acid methyl esters on biscyanopropyl siloxane phases

The selectivity of capillary columns coated with biscyanopropyl siloxane stationary phases for the separation of fatty acid methyl esters has been optimized by means of computer-assisted column temperature optimization software. Temperature programming rates yielding the highest resolution in the shortest analysis time were selected for split, splitless, and on-column injection operated in the constant pressure and pressure programmed modes.     

聚合物基板表面状态对异相接枝的影响研究

研究了对于羟丙基纤维素（HPC）基板进行表面修饰时,基板表面状态的调控 对基板表面化学接枝的影响。用双官能团化合物2,4-甲苯二异氰酸酯（TDI）作为 接枝桥梁,其对位的异氰酸酯基先和基板上的羟基反应,保留的邻位异氰酸酯基进 一步再与丙烯酸的羟基反应,让接枝在基板上的活性丙烯酸分子继续和丙烯酸溶液 聚合,通过这种途径在基板表面修饰聚丙烯酸。基板制备时,由于不同介质对HPC 基板表面的不同诱导作用,导致表面组成各异,大大影响了接枝反应的效果。红外 光谱和二次离子飞行时间质谱均证明了可以用2,4-甲苯-二异氰酸酯（TDI）分子 做接枝桥梁在基板表面异相接枝上羟基并进一步接枝聚丙烯酸,从而达到修饰基板 的目的。     

中药指纹图谱技术研究现状

中药指纹图谱特指中药样本经光谱或色谱等现代分析技术得到的中药各组分群体特征的图谱或图象。凭借实用的指纹图谱既可确认中药材或中药制剂的真伪,同时又能判断其质量的稳定与否。本文对中药指纹图谱技术研究领域内的国内外现状及主要技术进行了综述。     

General Information to Obtain Spherical Particles with Ordered Mesoporous Structures

Conditions for the synthesis of aluminum organophosphonate (AOP) and aluminophosphate (AlPO) spheres containing periodic mesopores were optimized and demonstrated to be general morphological controls for the surfactant‐assisted synthesis of mesoporous materials. High‐quality AOP and AlPO spheres with uniform mesopores were obtained at low and high temperatures, respectively. The aerosol‐assisted synthesis of materials with uniform mesopores was categorized by using the difference in relative density of soluble AOP and AlPO oligomers that interact with ethylene oxide (EO) units in EO_nPO_mEO_n triblock copolymer (PO=propylene oxide). Then, ordered mesoporous structures are constructed with the adequate amount of species in resultant frameworks, and the number of interactive points in soluble species determines the resultant density of the frameworks after self‐assembly. Consequently, temperature‐dependent synthesis, which allows controlled infiltration of soluble species to match the density of resultant frameworks, is required for the formation of ordered mesoporous structures under morphological control.