Characterisation and identification of proteinaceous binding media (animal glues) from their amino acid profile by capillary zone electrophoresis

A capillary electrophoretic method for identifying different species of proteinaceous binders--collagen, egg white, and milk casein--is described. It allows characterisation of the proteins on the basis of the amino acid profiles obtained after their acidic hydrolysis. The profiles of the underivatised amino acids are recorded directly by capillary zone electrophoresis at pH 2.26 with the aid of a conductivity detector, thus eliminating the need for a derivatisation step. Identification is carried out by means of different relative peak areas of the amino acids. A scheme is given for identification, which is based on the main markers, hydroxyproline, proline, glycine, glutamic acid, and serine and valine.     

Analysis of Amaryllidaceae alkaloids from Chlidanthus fragrans by GC-MS and their cholinesterase activity

The underivatized alkaloid mixture extracted from the bulbs of Chlidanthus fragrans Herb. was investigated by capillary GC/MS for the first time. Fifteen known Amaryllidaceae alkaloids of five structure types were identified. The main alkaloids were tazzetine (9, tazettine-type), chlidanthine (2, galanthamine-type), belladine (8, belladine-type) and lycorine (12, lycorine-type). The alkaloid extract from the bulbs showed promising human blood acetylcholinesterase (IC50 = 20.1 +/- 2.9 microg/mL) and human plasma butyrylcholinesterase (IC50 = 136.8 +/- 6.9 microg/mL) inhibitory activity.     

Adsorption of Polycation and Anionic Surfactant onto Iron Surfaces and the Inhibition of Carbon Dioxide Corrosion

The adsorption process of two polycations (pDADMAC and C‐PAM) with different charge densities has been investigated using the quartz crystal microbalance technique with dissipation monitoring (QCM‐D). The effect of the charge density of the polycation, the NaCl concentration, and the complexation with an anionic surfactant are addressed in this work. X‐ray photoelectron spectroscopy and atomic force microscopy were utilized to analyze the adsorbate with respect to the film coverage and film structure. The corrosion‐inhibiting performance of the films on high‐purity iron in a CO₂ saturated brine, at 25°C, 1 bar CO₂, and pH 4, was investigated by the linear polarization resistance technique. It was found that the polycations adsorbed onto the iron surface, but the corrosion rate of 1 mm yr^?1 was not lowered. However, the polycations formed a complex with an anionic surfactant, and such films showed excellent inhibition performance. Both films, of pDADMAC/SDS and of C‐PAM/SDS, lowered the corrosion rate of iron below 0.01 mm yr^?1. The SDS concentration was below the cmc. It is believed that the SDS adsorbed into the preadsorbed polycation film, forming a complex structure resulting in a hydrophobic and dense film.     

Comparison of portable devices for sub-ambient concentration measurements of methane (CH4) and nitrous oxide (N2O) in soil research

ABSTRACT

Production and consumption of methane (CH₄) and nitrous oxide (N₂O) in soils have a strong influence on global greenhouse gases (GHG) budgets. Therefore, it is crucial to precisely measure GHG fluxes at the soil–atmosphere interface. In upland soils, CH₄ and N₂O can be consumed by microbiological processes, and the respective concentrations can be lower than in the atmosphere, demanding highly sensitive gas analysing systems. Traditionally, soil air is sampled in vials and analysed in the laboratory by gas chromatography (GC). During the last decade, different technologies have been developed that allowed to build portable gas analysers that are able to measure sub-ambient gas concentration directly in the field. Here, we compared sub-ambient to ambient CH₄ and N₂O concentration values from four portable devices using different measurement technologies (a portable GHG analyser based on laser absorption spectroscopy [LAS], two portable Fourier transform infrared spectroscopy [FTIR] devices and a field gas analyser using photoacoustic spectroscopy [PAS]) to traditional GC analysis in the laboratory (a GC system equipped with a flame ionisation detector [GC-FID] and an electron capture detector [GC-ECD]). The accuracy and precision of photoacoustic spectroscopy measurements are strongly influenced by the water vapour content and non-target gases in the sampling air. We used an advanced set-up for a widely used PAS analyser enabling N₂O measurements at sub-ambient concentrations with similar precision and accuracy as the GC-ECD system. Measurements of CH₄ and N₂O by FTIR and LAS devices were in good agreement with the GC systems. We conclude that the portable devices are suitable for studies of GHG fluxes in the field. Thanks to their universal and portable character, LAS, PAS and FTIR devices represent useful alternatives to currently used technologies for field studies.     

Network diversity and supramolecular isomerism in copper(II)/1,2-bis(4-pyridyl)ethane coordination polymers

Reactions of copper(II) sources with 1,2-bis(4-pyridyl)ethane (bpe) yielded metal-organic networks with diverse topologies and dimensionalities. Compounds [Cu(bpe)₂(dmf)₂]_n(ClO₄)_2n·2ndmf (1·2ndmf), [Cu(bpe)₂(dmf)₂]_n(ClO₄)_2n·3.5ndmf (2·3.5ndmf), [Cu(bpe)₂(NO₃)₂]_n·2nH₂O (4·2nH₂O) and [Cu₂(bpe)(O₂CMe)₄]_n·0.7nH₂O (5·0.7nH₂O) have been isolated by altering the copper(II) source, the reaction solvent and the crystallization process. Compounds 1·2ndmf and 2·3.5ndmf consist of cationic [Cu(bpe)₂(dmf)₂]²⁺ repeating units assembled to 1D and 2D (4,4) networks, respectively, and represent supramolecular isomers due to the conformational isomerism of the bridging bpe molecules. Compound 4·2nH₂O consists of neutral mononuclear [Cu(dpe)₂(NO₃)₂] repeating units assembled to inclined interpenetrating (4,4) sheets describing an overall entanglement that is 3D in nature, and compound 5·0.7nH₂O consists of neutral dinuclear repeating units assembled to cross-linked 1D chains.     

A solid-phase microextraction GC/MS/MS method for rapid quantitative analysis of food and beverages for the presence of legally restricted biologically active flavorings

A method was developed using automated headspace solid-phase microextraction coupled with GC/MS/MS to simultaneously determine the presence of seven biologically active flavoring substances whose levels of use in processed foods is controlled by statutory limits. The method can be applied to identify and quantify the presence of 1,2-benzopyrone (coumarin), beta-asarone, 1-allyl-4-methoxybenzene (estragole), menthofuran, 4-allyl-1 ,2-dimethoxybenzene (methyl eugenol), pulegone, and thujone at levels ranging from 0.5 to 3000 mg/kg. The method has been optimized and validated for three different generic food types categorized on the basis of composition and anticipated use levels of flavorings and food ingredients. The food categories are alcoholic and nonalcoholic beverages; semisolid processed foods (e.g., soups, sauces, confectionary, etc.); and solid foods (muesli, bakery products, etc.). The method is simple, inexpensive, and rapid, and eliminates the use of flammable and toxic solvents. There is no sample preparation, and using MSIMS, unequivocal confirmation of identification is achieved even in highly complex matrixes containing many potential interfering volatiles. The method precision for spiked samples ranged from 2 to 21%, with the greatest variability associated with solid matrixes. The LOD and LOQ values were well below 0.1 and 0.5 mg/kg, respectively, in all cases for individual substances, fulfilling requirements for enforcement purposes. The robustness of the method was demonstrated in a small survey of retail samples of four spirits, five flavored milks, three energy drinks, five liqueurs, five soups, 10 sauces, five herbal teas, and three breakfast cereals.     

Multisided matching games with complementarities

The paper considers multisided matching games with transfereable utility using the approach of cooperative game theory. Stable matchings are shown to exist when characteristic functions are supermodular, i.e., agents' abilities to contribute to the value of a coalition are complementary across types. We analyze the structure of the core of supermodular matching games and suggest an algorithm for constructing its extreme payoff vectors. Received February 1997/Final version September 1998     

Soluble Polystyrenes Functionalized by Triorgano[(1‐oxoalkyl)oxy]stannanes (=Triorganotin Carboxylates): Synthesis,Structure, and Anion‐Recognition Characteristics

Polystyrene copolymers of the type ( P −H)_1−x( P −(CH₂)_n−COOSnR₃)_x containing [(1‐oxoalkyl)oxy]triphenylstannane or tributyl[(1‐oxoalkyl)oxy]stannanes as side chains ( P −H=styrene; P −(CH₂)_n−COOSnR₃ =para‐substituted styrene‐like monomeric unit with R=Ph (x=0.1), Bu (x=0.5); n=2–4) were investigated. The tributyl[(1‐oxoalkyl)oxy]stannane copolymer was prepared by direct conversion of the corresponding copolymeric methyl esters with hexabutyldistannoxane. By contrast, the [(1‐oxoalkyl)oxy]triphenylstannane copolymer could be prepared only by a procedure involving two reaction steps consisting of a preliminary hydrolysis of the related methyl ester ( P −H)_1‐x( P −(CH₂)_n−COOMe)_x followed by functionalization of the corresponding poly(carboxylic acid) ( P −H)_1‐x( P −(CH_2n−COOH)_x with hydroxytriphenylstannane. Attempts to directly convert the methyl ester with hydroxytriphenylstannane or hexaphenyldistannoxane led to the formation of uncompletely functionalized product. The structure of the stannane‐functionalized polymers was investigated in solution and solid state by NMR, IR, and thermal analysis. The tributylstannane and triphenylstannane copolymers were assessed as chloride‐selective anion carriers in polymeric‐liquid‐membrane potentiometric ion‐selective electrodes.     

ChemInform Abstract: Formation and Stability of Gaseous Ternary Oxides of Group 14-16 Elements and Related Oxides of Group 15 Elements: Mass Spectrometric and Quantum Chemical Study.

The formation of the new compounds PbTeO₃, PbTe₂O₅, Pb₂TeO₄, and Pb₂Te₂O₆ is observed in the gas phase by heating a mixture of solid PbO and TeO₂ at 1063 K using a mass-spectrometric Knudsen-cell method.