Composition and spectral studies of polyaniline salts

Five different polyaniline salts have been prepared by chemical polymerization of aniline in aqueous solution of different acids. The polyaniline base was obtained from the corresponding polyaniline salt by dedoping using aqueous ammonium hydroxide solution. Electron paramagnetic, electronic absorption, infrared spectral and conductivity measurements have been performed on the polyaniline salts and polyaniline bases. This composition and the extent of dopant in polyaniline salt systems have been determined. There is no definite correlation between the conductivity and the stoichiometric ratio between the polyaniline base and the acid, and also the spin concentration.     

Crystal structure and ionic conductivity of the series A2Bi24Mo8X2O68 (A = Ca, Sr and Ba and X = Cr and W) in the Bi2O3?MoO3 system

A series of A₂Bi₂₄Mo₈X₂O₆₈ compounds, Ca₂Bi₂₄Mo₈Cr₂O₆₈ (CBMC), Sr₂Bi₂₄Mo₈Cr₂O₆₈ (SBMC), Pb₂Bi₂₄Mo₈Cr₂O₆₈ (PBMC) and Ba₂Bi₂₄Mo₈W₂O₆₈ (BBMW) have been synthesized by the solid-state method and characterized by single crystal X-ray diffraction. The compounds index into the monoclinic P2/c system with a=11.687(4) ?, 5.784(2) ?, 24.728(9) ?, 101.911(6)°, Z=1; 11.673(6) ?, 5.775(3) ?, 24.670(2) ?, 101.757(8)°, Z=1; 11.638(3) ?, 5.790(1) ?, 24.655(6) ?, 101.716(4)°, Z=1 and 11.718(6) ?, 5.818(3) ?, 24.716(12) ?, 101.835(9)°, Z=1 for CBMC, SBMC, PBMC and BBMW, respectively. The structures were solved by direct methods and refined to R indices of 0.081, 0.065, 0.080 and 0.079 respectively. These compounds are isostructural with Bi₂₆Mo₁₀O₆₉ and the structure consists of columns of [Bi₁₂O₁₄] along the b-axis, surrounded by Mo/Cr/WO₄ tetrahedra. a.c. impedance studies indicate higher values of ionic conductivity for the tungsten-substituted compounds. Supplementary material The crystal data of CBMC, SBMC, PBMC and BBMW have been deposited at the Fachinformationszentrum Karlsruhe (FIZ) with the numbers CSD 415143, CSD 415145, CSD 415144 and CSD 415142, respectively.     

The hydrolysis mechanism of bis(2,4-di-tert-butyl)pentaerythritol diphosphite (Alkanox P24): An atmospheric pressure photoionisation mass spectrometric study

Alkanox P24 is a commercial phosphite antioxidant, well known in the literature for its excellent processing stability. As in the case of many processing phosphites, however, Alkanox P24 might undergo hydrolysis when exposed to small amounts of water. A number of products proposed recently in the hydrolytic pathway of the phosphite [Ortuoste N, Allen NS, Papanastasiou M, McMahon A, Edge M, Johnson B, et al. Polym Degrad Stab; 2006;91:195-211] are investigated in this study by atmospheric pressure ionisation-mass spectrometry (API-MS). The applicability of atmospheric pressure photoionisation (APPI) and atmospheric pressure chemical ionisation (APCI) ion sources is tested and the ion formation characteristics of Alkanox P24 are compared in both sources. In positive ion mode, ionisation of the parent phosphite occurred by protonation. In negative ion mode no pseudo-molecular ion peak was detected and the deprotonated species were more dominant in APPI. This source was employed further for the investigation of the hydrolysis products, since it exhibited lower limits of detection. High performance liquid chromatography (HPLC) with single ion monitoring (SIM) detection was used for the separation of the species formed. Hydrolysis of the phosphite proceeded via the scission of the two P-O_phenol bonds exclusively to give 2,4-di-tert-butyl phenol quantitatively as a final product.     

Effect of ionic additives on the elution of sodium aryl sulfonates in supercritical fluid chromatography

Addition of a small amount of polar solvent (i.e., modifier) to CO2 in packed column supercritical fluid chromatography (SFC) has shown major improvements in both polar analyte solubility and interaction of the polar analyte with the stationary phase. Recently, the addition of an ionic component (i.e., additive) to the primary modifier by one of us has been shown to extend even further the application of SFC to polar analytes. In this work, the effect of various ionic additives on the elution of ionic compounds, such as sodium 4-dodecylbenzene sulfonate and sodium 4-octylbenene sulfonate, has been studied. The additives were lithium acetate, ammonium acetate, tetramethylammonium acetate, tetrabutylammonium acetate, and ammonium chloride dissolved in methanol. Three stationary phases with different degrees of deactivation were considered: conventional cyanopropyl, deltabond cyanopropyl, and bare silica. The effect of additive concentration and additive functionality on analyte retention was investigated. Sodium 4-dodecylbenzene sulfonate was successfully eluted using all the additives with good peak shape under isocratic/isobaric/isothermal conditions. Different additives, however, yielded different retention times and in some cases different peak shapes.     

高电导率的a—SiHY合金的低温电导特性

用射央求地在硅单晶衬底上沉积出电导率高达６０Ｓ／ｃｍ的ａ－ＳｉＨＹ合金薄膜。在２０－３００Ｋ，对于钇含量高的样品，其电导仍是热激活的。ｌｇσ与１／Ｔ的关系曲线能够被拟合成斜率不同的两条直线，直线的斜率和两直线间拐点所地 温度依赖于膜中钇的含量。但对钇含量低的薄膜，电导对温度的依赖关系度为σ∝ｅｘｐ（－１／Ｔ＾１／４）。结果表明，这些钇含量不同的样品在没的温度范围内具有不同的导电机制。     

Acceleration of the Passerini reaction in the presence of nucleophilic additives

An accelerating effect of nucleophilic additives was revealed for the Passerini multi-component reaction. The influence of aqueous solutions on the reaction rate was studied in detail and the direct involvement of water in the bond-making step was attributed as the basis of an accelerating effect. Other nucleophiles were tested as alternatives to water; as a result N-hydroxysuccinimide is proposed as an accelerant of the Passerini reaction.     

Direct determination of sulfite in food samples by a biosensor based on plant tissue homogenate

In the work described here, a biosensor was developed for the determination of sulfite in food. Malva vulgaris tissue homogenate containing sulfite oxidase enzyme was used as the biological material. M. vulgaris tissue homogenate was crosslinked with gelatin using glutaraldehyde and fixed on a pretreated Teflon membrane. Sulfite was enzymatically converted to sulfate in the presence of the dissolved oxygen, which was monitored amperometrically. Sulfite determination was carried out by standard curves, which were obtained by the measurement of consumed oxygen level related to sulfite concentration. Several operational parameters had been investigated: the amounts of plant tissue homogenate and gelatin, percentage of glutaraldehyde, optimum pH and temperature. Also, some characterization studies were done. There was linearity in the range between 0.2 and 1.8 mM at 35 °C and pH 7.5. The results of real sample analysis obtained with the biosensor agreed well with the enzymatic reference method using spectrophotometric detection.     

New integrated measurement protocol using capillary electrophoresis instrumentation for the determination of viscosity, conductivity and absorbance of ionic liquid-molecular solvent mixtures

The low vapor pressure and the versatility of the physico-chemical properties of ionic liquids make them really attractive as an alternative for conventional molecular solvents. The knowledge of their physico-chemical properties (viscosity, conductivity, miscibility with organic solvents and anion-cation interactions) has appeared mandatory for better targeting their applications, although it is generally still lacking or incomplete.This work promotes capillary electrophoresis instrumentation as an integrated apparatus for measurement of viscosity, conductivity and absorbance of pure ionic liquids and ionic liquid-molecular solvent mixtures. Compared to current conventional techniques, the assets of this instrumentation for this purpose are the combined availability of a pressure delivery system, power supply, diode array absorbance detector and thermoregulation device, allowing unattended, automatic and easy operation, involving minimum sample handling. Most importantly, the required sample volume can be reduced to about 50 μL, making this protocol very cost-effective. A protocol was optimized with respect to time, sample consumption and data reliability for the determination of these physico-chemical parameters. Ionic liquids selected for method development and validation differed in the nature of their cation (butyl- and ethyl-methylimidazolium) and anion (trifluoromethanesulfonate and bis(trifluoromethanesulfonyl)imide). Various molecular solvents were mixed with these ionic liquids (acetonitrile, methanol, dimethylformamide and trifluoroethanol) and the same physico-chemical properties were determined by optimized methods. The knowledge of these data should be of great support in various application areas, including the development of new separation media for capillary electrophoresis and chromatographic techniques.     

Sequential optimisation of the separation of a complex mixture of plastics additives by HPLC with a quaternary gradient and a dual detection system

Summary The separation of two families of plastics additives (phenolic antioxidants and UV absorbers) has been achieved by high performance liquid chromatography with a quaternary gradient. A methodology of separation based on a sequential optimization is described. After a preliminary study of the effects of solvents on retention of compounds, the mobile phase is first chosen for each class of additives (Irganox and Tinuvin), then for the mixture of all the compounds and the separation is finally optimized. The importance of the column phase ratio is also reported. The use of two detectors, UV absorbance and light-scattering, enables all the compounds to be detected. The performance of the detectors has been compared and the effects of the nebulization temperature on the detection of low molecular mass compounds is reported.     

The use of ATR-IR to identify the components separated by paper chromatography

Summary A modified procedure for the identification of separated components in paper chromatography using attenuated total reflection infrared spectroscopy is described. This combined method, though inferior in sensitivity and resolution to the modern separation systems interfaced with sophisticated analytical instruments, is simple, relatively less expensive and suitable for routine analysis of components like polymer additives.