Comparison of capillary zone electrophoresis performance of powder-blasted and hydrogen fluoride-etched microchannels in glass

The applicability of glass chips with powder-blasted microchannels for electrophoretic separations was examined, and the performance was compared to microchannels etched with hydrogen fluoride (HF), using bicarbonate buffer and rhodamine B and fluorescein as model compounds. The measured electroosmotic mobilities in all chips were comparable, with values of ca. 7 x 10(-4) cm(2) V(-1)s(-1). The effect of electrical field strength and detection length on the separation efficiency was monitored. It was found that the main source of dispersion is of the Taylor-Aris type, which was discussed in relation to channel roughness differences. Although in powder-blasted channels with a separation length of 8.20 cm, 7-9 times lower plate numbers were obtained than in a HF-etched channel with similar dimensions, successful separation of five fluorescein isothiocyanate (FITC)-labeled amino acids was obtained on a powder-blasted chip within 80 s. Efficiencies of up to 360 000 plates/m were demonstrated on this chip, when a higher buffer concentration was used at a field strength of 664 V/cm. It can be concluded that powder-blasted microchannel chips, although they have a lower separation efficiency compared to HF-etched chips, perform well enough for many applications. Powder blasting can therefore be considered a low-cost and efficient alternative to HF etching, in particular because of the possibility to fabricate access holes through the glass with the same process.     

Solubility of room-temperature ionic liquid in supercritical CO2 with and without organic compounds

Ionic liquid can dramatically dissolve in supercritical (sc) CO2 with polar organic compounds (ethanol, acetone) especially as the concentration of the compounds in scCO2 exceeds 10 mol%, while the effect of a nonpolar organic compound (n-hexane) in scCO2 on the solubility is very limited even when its concentration is as high as 30 mol%.     

Polymeric enzyme mimics: catalytic activity of ribose-containing polymers for a phosphate substrate

The polymers containing ribose rings: poly(5'-acrylamido-5'-deoxy-1',2'-O-isopropylidene-alpha-D-ribose) (11), poly(5'-acrylamido-5'-deoxy-alpha-D-ribose) (12) and poly(5'-acrylamido-5'-deoxy-1'-O-methyl-D-ribose) (13) were prepared as enzyme mimics. Polymers 12 and 13 with free vic-cis-diol groups catalyzed the hydrolysis of phosphodiester (ethyl p-nitrophenyl phosphate and N-methylpyridinium 4-tert-butylcatechol cyclic phosphate) and phosphomonoester substrates with a rate acceleration of 10 approximately equal to 10(3) compared with the uncatalyzed reaction. They also catalyzed the reverse reactions, i.e., the esterification of phosphomonoester to phosphodiester and the phosphorylation of alcohols with phosphate ions. The catalytic activity was attributable to the vic-cis-diols of riboses on polymer chains, which formed hydrogen bonds with two phosphoryl oxygen atoms of phosphates so as to activate the phosphorus atoms to be attacked by nucleophiles. The catalytic activity was negligible for polymer 11 where vic-cis-diol groups were blocked with isopropylidene groups. The catalytic activity was attributable to the vic-cis-diols of riboses on polymer chains, which formed hydrogen bonds with two phosphoryl oxygen atoms of phosphates so as to activate the phosphorus atoms to be attacked by nucleophiles.     

Highly enantioselective iridium-catalyzed hydrogenation of heteroaromatic compounds,quinolines

The highly enantioselective hydrogenation of quinoline derivatives is developed using [Ir(COD)Cl]2/(R)-MeO-Biphep/I2 system, and this methodology has been applied to the asymmetric synthesis of three naturally occurring alkaloids angustureine, galipinine, and cuspareine. This method provided an efficient access to a variety of optically active tetrahydroquinolines with up to 96% ee.     

Experimental and theoretical characterization of H(2)OOO(+)

This report presents the preparation and characterization of H2OOO+, an important intermediate in water-oxygen chemistry. The H2OOO+ cation was produced by co-deposition of H2O/Ar with radio frequency discharged O2/Ar at 4 K and was identified by four fundamental infrared absorptions. Quantum chemical calculations indicate a doublet ground state with a H2O-O2 hemi-bonded Cs structure.     

A "sea urchin" family of boranes and carboranes: the 6m + 2n electron rule

A new family of related borane and carborane cages has been designed computationally. These compounds obey a new electron counting rule (6m + 2n rule) rather than Wade's rule. The structures of these cages can be conceived by combining m aromatic pyramidal and n aromatic triangular units. The interstitial electrons from the m pyramids (six electrons for each unit) and the n triangles (two electrons for each unit) constitute the total 6m + 2n skeletal electrons. The greater number of skeletal electron pairs in large closo-borane cages (e.g., B32H328- or C8B24H32) achieves stabilization through the optimal occupancy of all bonding orbitals. The favorable electronic structure, the large HOMO-LUMO gaps, the large lowest positive frequencies, and the local aromaticity of the pyramidal and triangular units (as demonstrated by the large negative NICS values) of the new large closo-cages auger well for their eventual experimental realization.     

Analysis of vasopressin using capillary electrophoresis with laser-induced fluorescence detector based on competitive immunoassay

A competitive immunoassay based on CE-LIF has been developed for the determination of vasopressin in biological mixtures. Vasopressin participates in the hormonal control of water metabolism and the constriction of arterioles in humans. Thus, detection of vasopressin is important in diagnosing pathological conditions and physiological water metabolism. The peptides were fluorescently tagged with FITC and purified by HPLC. The purified product was then mixed with the cerebrospinal fluid sample followed with the addition of anti-vasopressin antibody. It was possible to separate antibody-bound and free FITC-tagged vasopressin within 10 min by CE-LIF analysis using uncoated fused-silica capillary with high reproducibility.