Protonated ethanol and its neutral counterparts

Collisionally activated dissociation and neutralization-reionization experiments reveal that protonation of ethanol leads to two distinct isomers, the classical ion CH₃CH₂OH⁺₂ and the proton-bound complex C₂H₄…H⁺…OH₂. The neutral counterpart of the latter is unstable, whereas that of the former can be produced in a bound state if the CH₃CH₂OH⁺₂ precursor ion is formed under low ion source pressure conditions and, thus, with higher internal energies. This suggests that there are substantial differences in the geometries of CH₃CH₂OH⁺₂ and the hypervalent CH₃CH₂OH₂ ·. This provides only a partial explanation for unusual isotope effects; C₂H₅OD₂ ·, CH₃CD₂OD₂ ·, and CD₃CH₂OD₂ · are substantially more stable than C₂D₅OD₂ · and C₂H₅OH₂ ·.     

Determination of trace elements in bottled water in Greece by instrumental and radiochemical neutron activation analyses

Summary Four different bottled water brands sold in Greece in the winter of 2001-2002 were analyzed for a wide range of chemical elements, using neutron activation analysis (NAA). The elements Na and Br were determined instrumentally (INAA), whereas the other metals and trace elements radiochemically (RNAA). The results indicated that the mean level of all the elements determined in the samples were well within the European Union (EU) directive on drinking water and accomplish the drinking water standards of the World Health Organisation (WHO) as well as of the Food and Drug Administration (FDA).     

Analysis of fragrance compounds in blood samples of mice by gas chromatography, mass spectrometry, GC/FTIR and GC/AES after inhalation of sandalwood oil.

After inhalation experiments with sandalwood oil and the pure fragrance compounds coumarin and alpha-terpineol, substances were detected and measured in the blood samples of test animals (mice) using gas chromatography/mass spectrometry (GC/MS) (MID) in connection with GC/FTIR (SWC), GC/AES (carbon and oxygen trace) and flame ionization detection/gas chromatography. Using tiglinic acid benzyl ester as the internal standard the following concentrations in serum could be found: alpha-santalol 6.1 ng/mL, beta-santalol 5.3 ng/mL and alpha-santalene 0.5 ng/mL. In separate inhalation experiments with coumarin and with alpha-terpineol the corresponding concentrations were 7.7 ng/mL and 6.9 ng/mL, respectively.     

Morphology of Nylon-6 blends with styrenic polymers

The morphology of blends of styrenic polymers in a matrix of 75% Nylon-6 prepared in a Brabender Plasti-Corder was examined by scanning electron microscopy. Styrene/acrylonitrile copolymers (SAN) form smaller particles as the AN level increases owing to the corresponding decrease in the SAN–polyamide interfacial tension. Various styrenic polymers containing functional groups, maleic anhydride or oxazoline type, that can react with Nylon-6 during melt processing were added to the SAN phase which also led to a decrease in the particle size owing to the graft copolymer formed in situ. The effects of functional group type, amount of functional groups per chain, amount of functional polymer added, and the miscibility of the styrene/maleic anhydride (SMA) and SAN copolymers on the morphology of the styrenic phase in the Nylon-6 matrix are described. © 1992 John Wiley & Sons, Inc.     

The influence of synthetic conditions on the stability of methotrexate-monoclonal antibody conjugates determined by reversed phase high performance liquid chromatography.

Methotrexate (MTX) has been convalently attached to an IgG-type monoclonal antibody (791T/36) directed to tumour-associated antigen gp72. Conjugates were synthesized by the active ester method using MTX N-succinimidyl ester at various pH values (7.5-10.5). Following purification by gel filtration, high performance liquid chromatography was used to assess the free drug or its derivatives in samples of MTX-791T/36 conjugates previously treated (or not) with hydroxylamine. Quantitative analysis, performed on a reversed phase column (pore size 300 A) with isocratic acetonitrile-sodium acetate buffer (pH 4.8) as mobile phase, indicated no detectable amount of free methotrexate in hydroxylamine-treated conjugates even six months after their preparation. Similar observations were made with conjugates, whose synthesis were performed at pH greater than or equal to 10. In contrast, the presence of increasing amounts of drug/metabolite could be demonstrated in samples produced at lower pH values. Based on these findings, the pH-dependent kinetics of MTX release has been determined and used to design conditions under which stable MTX-791T/36 conjugates could be prepared without hydroxylamine reaction.     

Ultraviolet photoemission spectroscopy of hydrogen complex deactivation on InP:Zn(1 0 0) surfaces

Ultraviolet photoemission spectroscopy is used to study the kinetics of the H-Zn complex deactivation in Zn doped InP(1 0 0). Hydrogen injected into the material electronically passivates the local carrier concentration. Reverse-biased anneals of the InP under ultra-high vacuum show a dramatic change in the work function of the material with increasing temperature. Spectral features are also shown to be sensitive to sample temperature. To our knowledge, we show the first view of hydrogen retrapping at the surface using photoemission spectroscopy. A simple photoelectron threshold energy analysis shows the state of charge compensation of the material.     

New ferroelectric and antiferroelectric liquid crystalline materials containing differing numbers of lactate units

A new series of chiral liquid crystalline materials having the same rigid core containing a keto group, and various numbers of ( S )-lactate groups in the chiral segment, has been synthesized and studied. All the compounds contain a branched terminal alkyl chain derived from ( S )-2-methylbutanol. The influence of the number of lactate units on mesogenic behaviour has been studied. All the compounds show the paraelectric SmA phase and the ferroelectric SmC * phase over rather wide temperature ranges. The antiferroelectric SmC * A phase was observed for the compound possessing two lactate groups.