Performance of throughout in-capillary derivatization capillary electrophoresis employing an on-line sample and run buffer loading device

We report on the effect on performance of varying the length of the capillary during throughout in-capillary derivatization (TICD) capillary electrophoresis (CE). Performance was evaluated by on-line coupling with a sample and CE runbuffer loading device that was newly introduced for this study. The device was assembled with a low cost using two 5 mm inner diameter (ID) disposable polyethylene syringes. First, a sequence was manually formed consisting of a 200 microL run buffer solution plug, a 100 microL sample plug and another 200 microL run buffer solution plug. Each plug was separated from its neighbor by a 100 microL air plug. When each plug reached the injection point where both a platinum-wire anode and the end of the separation capillary tube were located, 340 V/cm separation voltage (electrophoresis voltage) and 34 V/cm injection voltage were applied to the capillary for 3 s. Then the analytes were derivatized during migration in 50 microm ID capillaries filled with 2 mM o-phthalaldehyde (OPA)/N-acetylcysteine (NAC) in a 20 mM phosphate-borate buffer (pH 10), followed by separating and detecting of OPA derivatives by absorbance of 340 nm. Derivatization, separation, and detection were performed systematically using capillaries which varied in length from 5 to 80 cm. In the case of TICD-CE of a mixture containing 1 mM aspartic acid (Asp) and 20 mM m-nitorophenol (MNP) as a test solution, it was determined that peak area and peak width ratios of Asp to MNP did not depend on capillary length. Enantiomeric separations of DL-alanine (Ala) and Asp were examined using a run buffer consisting of a 45 microM beta-cyclodextrin (CD)-2 mM OPA/NAC-20 mM phosphate-borate buffer (pH 10). Even though the resolution of these enantiomeric pairs decreased with decreasing capillary length, as expected, the peaks corresponding to both enantiomeric amino acids were identified even when a 5 cm capillary was used. An 8-component amino acid mixture was also tested with 5 cm and 10 cm capillaries.     

Ion-Selective Electrodes Based on Bilayer Film Coating

The electrode characteristics of ion-selective electrodes (ISEs) for K⁺, Na⁺, NH₄ ⁺, and Ca²⁺ based on bilayer film coatings, where the inner layer films are electroactive electropolymerized ones and the outer layer films are composed of conventional ion-sensitive materials, have been examined. These ISEs of the coated-wire electrode type have no conventional internal reference solution and reference electrode, but the inner films may be considered to function as the “internal standard solution.” The ion selectivity coefficients and the activity range showing Nernstian response were almost comparable to those of conventional liquid-membrane electrodes. The bilayer-coated ISEs showed insensitivity to O₂ and CO₂, long-term stability, and little drift. It was also found that the electrode performance is practically unchanged after sterilization in an autoclave. The results demonstrate that the bilayer-coated ISEs examined are promising for the determination of K⁺, Na⁺, NH₄ ⁺, or Ca²⁺ activity in biological and environmental systems.     

Ti complex catalysts including thiobisphenoxy group as a ligand for olefin polymerization

Titanium complexes were prepared by the reaction of 2,2′-thiobis(6-tert-butyl-4-methylphenol) (TBP) with TiCl₄ or Ti(OPrⁱ)₄. These complexes in combination with methyalumoxane as cocatalyst are highly active towards ethylene and propene, giving polymers having high molecular weights. The polymerization activities for ethylene and propene are comparable to those of Cp₂ZrCl₂-MAO catalyst. Polypropylene obtained had extremely high molecular weight (Mw>6 million) and low regioregularity (30% of head-to-head and tail-to-tail linkages). Highly syndiotactic polystyrene was obtained with these catalysts with activity up to 27 kg polymer per g Ti and hour. Copolymerization of styrene with ethylene gave highly alternating copolymer with isotactic styrene units. These catalysts are also active toward both conjugated and nonconjugated dienes such as butadiene and 1,5-hexadiene. Polybutadiene had mainly cis-1,4-structure (98%). The structure of poly(1,5-hexadiene) is rather complicated, which is quite different from that prepared with heterogeneous TiCl₃ catalysts.     

A mycelium with polyelectrolyte complex-bunched hyphae: preparation and fermentation performance

We studied the immobilization of a mycelium (Aspergillus niger) using the working hypothesis as follows: (a) when polycation was added to the cell suspension, a few parts of it would bind on the surface of a hypha, allowing to gather the hyphae in part but not all; (b) upon further addition of polyanion, such a gathering of the hyphae is tightly bunched by the polyelectrolyte complex (PEC) which is resulted from the remaining polycation; (c) as a result, a mycelium with partially bunched hyphae can be obtained. Potassium poly(vinyl alcohol) sulfate and trimethylammonium glycol chitosan iodide [6-O-(2-hydroxyethyl-2-(trimethylamonio)-chitosan iodide) were used as the polyanion and the polycation, respectively. The optical and electron microscopic analyses showed that our immobilized cell contains many of PEC-bunched hyphae. The sedimentation rate increased with the weight ratio of PEC to dry cells and leveled off at the weight ratio larger than 0.5. The gluconic acid production from glucose was studied by a semi-large scale (1 l) cultivation of the imobilized and free cells using a jar fermentor. It was found that an apparent specific activity of the immobilized cells for glucose oxidation becomes 1.44 times that of the free cells even at a high cell density of 40 g/l.     

Effect of co-catalyst system on α-olefin polymerization with rac- and meso-[dimethylsilylenebis(2,3,5-trimethyl-cyclopentadienyl)]zirconium dichloride

Propene, 1-butene and 1-hexene polymerization was conducted with a mixture of rac- and meso-[dimethylsilylenebis((2,3,5-tetramethyl-cyclopentadienyl))]zirconium dichloride (Me₂Si(2,3,5-Me₃Cp)₂ZrCl₂) ( 1 ) combined with methylaluminoxane (MAO), triethylaluminium (AlEt₃)/triphenylcarbenium tetrakis(pentafluorophenyl)borate (Ph₃CB(C₆F₅)₄) ( 2 ) and triisobutylaluminium (AliBu₃)/Ph₃CB(C₆F₅)₄, respectively, as co-catalyst systems. The ratios of polymerization rates R_p(rac)/R_p(meso) were changed with the combined cocatalysts. It was found that in the case of using trialkylaluminium/ 2 as co-catalyst R_p(rac)/R_p(meso) is lower than when using MAO in any kind of α-olefin polymerization.     

Study of molecular size in ethylene-propene copolymerization with zirconocene and hafnocene catalysts

Ethylene-propene copolymerization was carried out with Cp₂MCl₂ (Cp = cyclopentadienyl), rac-Et(Ind)₂MCl₂, rac-Me₂Si(Ind)₂MCl₂ (Et = ethylene, Me₂Si = dimethylsilyl, Ind = indenyl, M = Zr or Hf)/methylaluminoxane. In the case of using ansa-hafnocenes, the minimum molecular size (extended chain length) of ethylene-propene copolymer was obtained at about 50 mol-% of propene content in the copolymer. The polymerization activity decreased with increase of propene feed ratio in non-bridged non-specific metallocenes. Higher polymerization activities were observed for the copolymerization compared to ethylene and propene homo-polymerization with ansa-isospecific metallocenes. The factor of molecular size lowering was studied by the chain propagation and chain transfer reaction.     

Drag reduction and heat transfer in surfactant solutions with excess counterion

We present the results of a study of turbulent drag reduction in a small circulating loop using surfactant solutions with excess counterion. In addition, these solutions were used in measurements of heat transfer, both in pipe flow and in an impinging jet. Both frictional drag and heat transfer were reduced in the pipe flow experiments. Measurements of heat transfer in the impinging jet revealed a dependence on the molar concentration ratio of the counterion. When the counterion was added at a molar concentration 30 times higher than that of the surfactant, the resulting surfactant solution did not reduce the rate of heat transfer in the impinging jet. By using this surfactant system in an impinging jet, we show both a reduction in pipe friction and normal heat transfer potential in a circulating heat exchange system. In order to investigate this difference in heat transfer between pipe flows and impinging jet flows, a comparison was made of the wall shear stress between these two flow regimes. The estimated wall shear stress was of the same order in both flows, and thus was not considered to be the primary cause of the difference in heat transfer. It is instead suggested that the micellar structure of the surfactant is influenced by a compressive deformation of the impinging flow in a manner that is different from the shear deformation observed in pipe flow.     

Observation of the 7 MeV excited spin-flip and non-spin-flip partners in 16 ΛO by γ -ray spectroscopy

We have observed three γ -ray transitions in _Λ ¹⁶ O from both 7MeV excited spin-flip and non-spin-flip partners ( 2^-, 1^- ₂ to the ground-state doublet ( 1^- ₁, 0^- via the ¹⁶O(K ^-,π^-) reaction. The 7MeV excitation energies of the spin-doublet members ( 2^-, 1^- ₂ were determined to be 6784±4±4 keV and 6562±1±2 keV, respectively, and thus the spacing was obtained to be 222±4±5 keV. This is the first observation of the spin-flip state directly populated by the ( K ^-,π^- reaction. Moreover, such directly populated spin-flip and non-spin-flip partners were resolved for the first time.