Nonaqueous capillary electrophoretic separation of basic enantiomers using octakis(2,3-O-dimethyl-6-O-sulfo)-gamma-cyclodextrin, a new, single-isomer chiral resolving agent

The enantiomers of 34 pharmaceutical weak-base analytes were separated by nonaqueous capillary electrophoresis in acidic methanol background electrolytes using the sodium salt of the new, single-isomer chiral resolving agent, octakis(2,3-O-dimethyl-6-O-sulfo)-gamma-cyclodextrin (ODMS). The effective mobilities, separation selectivities and peak resolution values of the weak-base analytes were determined as a function of the ODMS concentration in the 0-40 mM range and were found to follow the theoretical predictions of the charged resolving agent migration model (CHARM model) modified for ionic strength effects. Fast, efficient separations were achieved for both comparatively small and large enantiomers.     

Synthesis and stereochemistry of stereoisomeric 1,3-benzoxazino-1,3- and -3,1-benzoxazines

Partly saturated 3,1-benzoxazino[1,2-c][1,3]benzoxazines and 1,3-benzoxazino[3,2-c][1,3]benzoxazines were prepared in one-pot syntheses from different cyclic 1,3-aminoalcohols by treatment with salicylaldehyde or 5-bromosalicylaldehyde, followed by formaldehyde. The structures of tetracycles 3a and 5 were determined by means of X-ray diffraction.     

Application of self-assembly for replacing chromate in corrosion protection of zinc

Due to the toxic and carcinogenic properties of hexavalent chromium ion, the corrosion protection with chromating technique needs replacement. Several environmentally friendly alternative metal pretreatments have already been proposed. One of these methods is the application of self-assembling molecules to form mono- or multilayers on the metal surfaces. These layers can prevent metal dissolution due to their dense and stable structure. The objective of our studies was to protect zinc surface against corrosion, with a thin phosphonate layer. Aqueous solutions of diphosphonic acid with different alkyl chain lengths were applied with different treatment times. The layer formation, stability, and corrosion protection of these films were monitored by electrochemical impedance spectroscopy and the effect of 1,5-diphosphono-pentane (DPP) on zinc was studied by polarization curves. The wetting properties were determined by static contact angle measurement. 1,5-Diphosphono-pentane forms a thin layer, with a pronounced protective ability in neutral aqueous solutions. The application of self-assembling molecules can be a promising method to replace the chromating technique on zinc surface.     

ICP-AES detection of silicon carbide impurities volatilized in a graphite furnace with the use of carbon tetrachloride vapour

The analytical capability of high-temperature halogenation with carbon tetrachloride vapour in a graphite furnace was investigated for silicon carbide powder with known chemical composition and particle size. Intensity vs heating time curves were determined for analytical lines of Al, B, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Ti, V and Si constituents, volatilized with and without the presence of CCl₄ vapour in the furnace atmosphere. Igniting 10 mg SiC at 2100 °C for 60 s in chlorinating atmosphere, the evaporated fraction of most of the constituents was higher than 90% (for Al about 50%). The line intensity vs sample mass (4–26 mg) relationships were linear for all impurities studied, while the intensity of silicon line showed a relatively small change with the sample mass. BEC (background equivalent concentration) values for this solid sampling technique (10 mg loaded sample) were 2–20 fold lower than those calculated for the conventional solution sample introduction method.     

Mechanism of the condensation reaction between 1-aryl- and heteroaryl-1,4-dihydro-3(2H)-isoquinolinones and aldehydes

4-Benzylidene-1-phenyl-1,4-dihydro-3(2H)-isoquinolinone, the intermediary product of the carbonyl condensation reaction between 1-phenyl-1,4-dihydro-3(2H)-isoquinolinone and benzaldehyde, rearranges in the presence of an equivalent quantity of sodium hydride into 4-benzyl-1-phenyl-3(2H)-isoquinolinone. As the possibility of the migration of the hydrogen at C-1 in the form of a proton or a hydrogen atom (radical reaction) was excluded, the mechanism of the rearrangement could be depicted as an intermolecular hydride anion migration. In case of the 1-(4-pyridyl)- and 1-(3-pyridyl)-1,4-dihydro-3(2H)-isoquinolinones, however, the rearrangement can be carried out also in polyphosphoric acid and in this case a proton loss-proton gain mechanism was proved.     

Determination of Pt in urine of tram drivers by sector field inductively coupled plasma mass spectrometry

The Platinum Group Elements (PGEs) used in automotive catalytic converters are partly emitted into the air during use and can enter the human respiratory system. Due to the increasing use of automotive catalytic converters, the importance of this problem cannot be overlooked.The goal of this investigation was to determine the concentration of Pt in the urine of individuals occupationally exposed to urban air with heavy traffic. Sector field inductively coupled plasma mass spectrometry (SF–ICP–MS) was used for determination of Pt in the urine of tram drivers. 38 and 34 subjects were investigated in Vienna and Budapest, respectively. Samples were taken from the tram drivers both before and after the shift.The results for Pt were compared to those from a previous study performed by our team. The comparison showed that the concentration medians were 4 times higher than the previous ones. Moreover, the values in Budapest were about twice as high as those from Vienna. A partly significant change could be observed between the two sets of data: before, and after the shift.     

Mass spectra of substituted pyrrolidine-N-oxyl radicals

Electron impact mass spectra of 65 pyrrolidine-N-oxyl derivatives have been assigned on a ‘peak-to-subgraph’ basis. On average, 50% of the total ion current is represented by structurally significant fragments associated with the nitroxide group. Secondary fragmentation is, as a rule, of a minor importance (30%), and fragments due to functional groups other than NO^· seldom contribute more than 10% of the total ion current An enhanced specificity of fragmentation is observed when one or more of the 2,2, 5,5-methyl groups is replaced by a longer aliphatic chain or an aromatic group.     

Partial Synthesis and Characterization of the Mono-and Diepoxides of β-Cryptoxanthin

β-Cryptoxanthin ( 1 ) was acetylated and then epoxidized with monoperoxyphthalic acid. After hydrolysis, repeated chromatography, and crystallization, (3S,5R,6S)-5,6-epoxy-β-cryptoxanthin ( 3 ), (3S,5S,6R)-5,6-epoxy-β-cryptoxanthin ( 4 ), (3R,5′R,6′R)-5′,6′-epoxy-β-cryptoxanthin ( 5 ), (3S,5R,6S,5′R,6′S)-5,6:5′,6′-diepoxy-β-cryp-toxanthin ( 6 ), and (3S,5S,6R,5′S,6′R)-5,6:5′,6′-diepoxy-β-cryptoxanthin ( 7 ) were isolated as main products and characterized by their UV/VIS, CD, ¹H- and ¹³C-NMR, and mass spectra. The comparison of the carotenoid isolated from yellow, tomato-shaped paprika (Capsicum annuum var. lycopersiciforme flavum) with 3–5 strongly supports the structure of 3 for the natural product.     

Analysis of cyanobacterial toxins (anatoxin-a, cylindrospermopsin, microcystin-LR) by capillary electrophoresis

Capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) were applied to the simultaneous separation of cyanobacterial toxins (anatoxin-a, microcystin-LR, cylindrospermopsin). The analytical performance data of both methods, optimized for the three toxins, were similar with a precision of migration times smaller than 0.8 RSD% and a detection limit in the range of 1-4 microg/mL, using spectrophotometric detection at 230 nm. Both methods were applied to an analysis of cyanotoxins in water bloom samples and crude cyanobacterial extracts. The results obtained indicate that, for complex matrices, the sequential application of CZE and MEKC is necessary. It is recommended to use both CE techniques for the analysis of the same sample in order to confirm the results by an orthogonal approach.     

Hydrolytically stable, diaminocarboxylic acid-based membranes buffering in the pH range from 6 to 8.5 for isoelectric trapping separations

Diaminocarboxylic acid carrier ampholytes, such as L-histidine, 2,3-diaminopropionic acid, L-ornithine, and L-lysine, were reacted with glycerol-1,3-diglycidyl ether (GDGE) and poly(vinyl alcohol) (PVA) in the presence of sodium hydroxide to produce hydrolytically and mechanically stable hydrogels, supported on a PVA substrate, for use as buffering membranes in isoelectric trapping (IET) separations. The pH values of the DACAPVA membranes were determined with the help of small-molecule pI markers and proteins and were found to be in the 6 < pH < 8.5 range. The membranes were successfully used to isoelectrically trap small ampholytes, desalt ampholyte solutions in IET mode, and effect the binary separation of chicken egg white proteins.