Catalytic <Emphasis Type="Italic">N</Emphasis>-Alkylation of Amines with Primary Alcohols over Halide Clusters

Piperidine was reacted with methanol under a hydrogen stream in the presence of (H₃O)₂[(W₆Cl₈)Cl₆]·6H₂O supported on silica gel. When the temperature was raised above 200 °C, the catalytic activity of the cluster appeared. Piperidine N-methylation proceeded yielding N-methylpiperidine in 95% selectivity at 350 °C. The corresponding halide clusters of niobium, molybdenum, and tantalum supported on silica gel also catalyzed the reaction. Primary alcohols such as ethanol and 1-propanol produced the corresponding N-alkyl products of piperidine; however, secondary and tertiary alcohols did not. Selective N-methylation of pyrrolidine, hexamethyleneimine, butylamine, and aniline also proceeded. Thus, the clusters catalyzed alkylation of aliphatic, alicyclic, and aromatic amines with primary alcohols. A Brønsted acid site attributable to a hydroxo ligand, which is formed on the cluster complex by thermal activation, is proposed as the active site of the catalyst.     

The inhibition abilities of multifunctional polyelectrolytes for silica scale formation in cooling water systems: role of the nonionic functional group

The abilities of multifunctional polyelectrolytes to enhance aluminum hydroxide dispersion and inhibit silica scale formation were examined in a pilot cooling water system. The following multifunctional polyelectrolytes were studied: a terpolymer of acrylic acid (AA), 2-acrylamide-2-methyl propane sulfonic acid (SA) and N-vinylpyrrolidone (NVP) (P(AA/SA/NVP)), acrylic acid homopolymer (P(AA)) and a copolymer of AA and SA (P(AA/SA)). The order of inhibition ability was P(AA/SA/NVP)>P(AA/SA)>P(AA), and was consistent with that of the dispersing ability for aluminum hydroxide. Other terpolymers incorporating different nonionic monomers were also examined and factors affecting their inhibition abilities were investigated, based on interaction energies calculated by density functional theory. Based on the correlation between scale inhibition abilities and interaction energies, we elucidated that the effective nonionic monomer of terpolymer for silica scale inhibition had low affinity for aluminum hydroxide and high affinity for H(2)O and Si(OH)(3)O(-). The affinities of nonionic monomer for aluminum hydroxide and H(2)O suggested that there was proper conformation of polyelectrolyte adsorbed for effectively dispersing aluminum hydroxide. Also, high affinity of nonionic monomer for Si(OH)(3)O(-) suggested that interacting Si(OH)(3)O(-) is an important role of inhibition of silica scale formation.     

Detection of 22 antiepileptic drugs by ultra-performance liquid chromatography coupled with tandem mass spectrometry applicable to routine therapeutic drug monitoring

The purpose of this study was to develop an ultra‐performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) method of 22 antiepileptics for routine therapeutic monitoring. The antiepileptics used in the analyses were carbamazepine, carbamazepine‐10,11‐epoxide, clobazam, N‐desmethylclobazam, clonazepam, diazepam, N‐desmethyldiazepam, ethosuximide, felbamate, gabapentin, lamotrigine, levetiracetam, N‐desmethylmesuximide, nitrazepam, phenobarbital, phenytoin, primidone, tiagabine, topiramate, valproic acid, vigabatrin and zonisamide. After protein precipitation of 50 μL plasma with methanol, the supernatant was diluted with water or was evaporated to dryness and reconstituted with mobile phase in the case of benzodiazepines. Separation was achieved on an Acquity UPLC BEH C₁₈ column with a gradient mobile phase of 10 mm ammonium acetate containing 0.1% formic acid and methanol at a flow rate of 0.4 mL/min. An Acquity TQD instrument in multiple reaction monitoring mode with ion mode switching was used for detection. All antiepileptics were detected and quantified within 10 min, with no endogenous interference. All the calibration curves showed good linearity in the therapeutic range (r² < 0.99). The precision and accuracy values for intra‐ and inter‐assays were within ±15% except for phenobarbital and tiagabine. A good correlation was observed between the concentration of clinical samples measured by the new method described here and the conventional methods. The values of carbamazepine and phenytoin by UPLC‐MS/MS were lower than those detected by the immunoassays, which might be caused by the cross‐reaction of antibodies with their metabolites. In conclusion, we developed a simple and selective UPLC‐MS/MS method suitable for routine therapeutic monitoring of antiepileptics. Copyright © 2012 John Wiley & Sons, Ltd.     

Path-integral molecular dynamics simulations of hydrated hydrogen chloride cluster HCl(H2O)4 on a semiempirical potential energy surface

Path-integral molecular dynamics simulations for the HCl(H₂O)₄ cluster have been performed on the ground-state potential energy surface directly obtained on-the-fly from semiempirical PM3-MAIS molecular orbital calculations. It is found that the HCl(H₂O)₄ cluster has structural rearrangement above the temperature of 300 K showing a liquid-like behavior. Quantum mechanical fluctuation of hydrogen nuclei plays a significant role in structural arrangement processes in this cluster.     

Evaluation of dispersion in a flow injection system by electrochemical detector and personal computer

Summary The evaluation of dispersion in a FIA system, which is one of the indices of analytical sensitivity and separation, has been studied with an electrochemical detector and personal computer. Two different modes are applied to evaluate the degree of dispersion. One is a flat portion type mode, the other a hanging bell type mode. From these experiments it is possible to easily estimate the degree of dispersion in a FIA system concerning low dispersion (1 < D < 3) and medium dispersion (3 < D < 10), as discussed by Ruzicka and Hansen. Two regulation methods for sample volume in a FIA system are also discussed.

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Untersuchung der Dispersion in einem Fließinjektionssystem mit Hilfe von elektrochemischem Detektor und Personal Computer

Zusammenfassung Die Dispersion in einem Fließinjektionssystem, die für die analytische Empfindlichkeit und Trennung von Bedeutung ist, wurde nach zwei verschiedenen Methoden ausgewertet. Es ergab sich, daß der Dispersionsgrad im niederen (1 < D < 3) und mittleren Bereich (3 < D < 10) (entsprechend den Untersuchungen von Ruzicka und Hansen) leicht berechnet werden kann. Zwei verschiedene Regulierungsmethoden für das Probevolumen in einem FIA-System werden ebenfalls diskutiert.

     

Coupling reactions of aryl and heteroaryl halides with a trimethylsilylethynylpyrazine

By the coupling reactions of trimethylsilylacetylene and 2-chloro-3,6-diisobutylpyrazine, 3,6-diisobutyl-2-trimethylsilylethynylpyrazine or 1,2-bis(3,6-diisobutylpyrazin-2-yl)acetylene was obtained, depending on the solvent used. The former substance coupled with various aryl and heteroaryl halides to give 1-aryl-2-pyrazin-ylacetylenes.     

Enzyme sensor for L-lactate using differential pulse amperometric detection

An enzyme sensor using differential pulse (DP) amperometric detection has been developed based on the measurement of the reduction current of the oxidized form of -nicotinamide adenine dinucleotide (NAD⁺) consumed by an enzyme reaction. This biosensor has the definite advantage to prevent interference caused by electrooxidative species such as ascorbate and uric acid and exhibits higher sensitivity and selectivity in comparison to the classical DC amperometric detector. The linear detection range of this biosensor was 5.0×10^–5 — 5.0×10^–4 mol/l and the relative standard deviation (R.S.D.) at 2.5×10^–4 mol/l was 5.0%.     

Kinetics and stability of CH4-CO2 mixed gas hydrates during formation and long-term storage.

The formation of CH4-CO2 mixed gas hydrates was observed by measuring the change of vapor-phase composition using gas chromatography and Raman spectroscopy. Preferential consumption of carbon dioxide molecules was found during hydrate formation, which agreed well with thermodynamic calculations. Both Raman spectroscopic analysis and the thermodynamic calculation indicated that the kinetics of this mixed gas hydrate system was controlled by the competition of both molecules to be enclathrated into the hydrate cages. However, the methane molecules were preferentially crystallized in the early stages of hydrate formation when the initial methane concentration was much less than that of carbon dioxide. According to the Roman spectra, pure methane hydrates first formed under this condition. This unique phenomenon suggested that methane molecules play important roles in the hydrate formation process. These mixed gas hydrates were stored at atmospheric pressure and 190 K for over two months to examine the stability of the encaged gases. During storage, CO2 was preferentially released. According to our thermodynamic analysis, this CO2 release was due to the instability of CO2 in the hydrate structure under the storage conditions.     

Nano-aquarium with microfluidic structures for dynamic analysis of Cryptomonas and Phormidium fabricated by femtosecond laser direct writing of photostructurable glass

We demonstrate fabrication of microchips with microfluidic structures for dynamic analysis of living cells using a femtosecond (fs) laser. Fs laser direct writing followed by annealing and successive wet etching in dilute hydrofluoric (HF) acid solution resulted in formation of three dimensional (3D) hollow microstructures embedded in photostructurable glass. The embedded microchannel structure enabled us to analyze unique phenomenon of Cryptomonas, which suddenly swims very fast under certain condition. Vector analysis of the driving force for the rapid motion was also carried out by introducing nano-beads into the microchannel, in which Cryptomonas was encapsulated. We also fabricated a microchip for observation of Phormidium moving toward a seedling root, which accelerates growth of the seedling. Using the embedded microchannel in the microchip, observation of Phormidium assemblage to the seedling root was easily carried out. Such microchips with microfluidic structures, referred to as a nano-aquarium, realize the efficient and highly functional observation of living cells.