Experimental study for adsorption and photocatalytic reaction of ethyl methylphosphonate molecule as organophosphorus compound adsorbed at surface of titanium dioxide under UV irradiation in ambient condition

The adsorption and photocatalytic degradation of Ethyl methylphosphonate (EMPA) on powdery TiO₂ film has experimentally investigated using attenuated total reflection-infrared Fourier transform spectroscopy (ATR-FTIR) in ambient condition. Characteristic IR frequency as P-O-C vibration mode as EtO was observed by EMPA adsorbed at the surface of TiO₂. By TiO₂ photocatalysis, the adsorbed EMPA was decomposed to methyl phosphonic acid and phosphoric acid. The increment of IR intensity of which is assigned to Ti–O-P-O-Ti of EMPA was accompanied with increasing the IR peak intensity assigned to MPA. About that, we suggest that the appearance of the Ti–O-P-O-Ti of EMPA by the TiO₂ photocatalysis is regarded as acceleration of the hydrolysis of EMPA by the surface OH groups of TiO₂. The plausible adsorption structure and the photocatalytic reaction mechanism of EMPA at the surface of TiO₂ photocatalyst were elucidated.

     

Development and features of hydro-membrane gas chromatography.

Hydro-membrane gas chromatography (HMGC) is achieved by the annular condensation of water in a capillary column at less than 70 degrees C. The annular membrane of water is formed as a result of the wettability of the stationary phase, which is induced at a water contact angle ranging from 75 degrees to 79 degrees, as derived from a solubility parameter (delta) range of 15.7 +/- 0.3 MPa(1/2) of the coated resin. The range of the liquid to gas volume ratio (beta) required to support the annular membrane should be kept between 0.00005 and 0.0003. In the case of a 0.25-mm i.d. column, the ratio can be set by the combination of a 0.1 to 0.2 microl min(-1) water supply rate and helium gas flow rate. Separation by HMGC develops not only a gas-solid partition but also a focusing effect on the water membrane. One feature of HMGC is that it gives a non-adsorption chromatogram based on the blocking effect of pre-adsorbed water; furthermore, despite the presence of a relatively large quantity of water, the electron impact ionization efficiency is kept the same as in the usual GC/MS condition. The detection limit with the injection of 1 microl of aquatic solution was estimated to be less than 0.1 ppb of low-molecular-weight fatty acids with s/n = 5 on a mass chromatogram at m/z 45. The HMGC/EI-MS system can be applied to the trace analysis of C1 to C3 volatile acids, volatile inorganic acids, and halogenated organic acids in water.     

Absorption of diltiazem in beagle dog from pulsatile release tablet.

An orally applicable pulsatile drug delivery system in dry-coated tablet form was prepared using diltiazem hydrochloride as the model drug, and a polyvinyl chloride-hydrogenated castor oil-polyethyleneglycol mixture as the outer shell of the tablet. In vitro drug release from the prepared tablet exhibited a typical pulsatile pattern with a 7 h lag phase (non-drug release period). This dosage form was orally administered to three beagle dogs under non-fasting and fasting conditions, and the plasma concentration level of diltiazem was determined according to time after administration. The result of the in vivo study in non-fasting dogs suggested that the drug could be released in the gastrointestinal tract as in the in vitro test. However, under the fasting condition, a large difference in the plasma concentration profile was found, suggesting that the disintegration time of the tablet tended to be influenced by the feeding condition of subject.     

Lewis acid-mediated selective chlorinations of silyl enolate

A new method involving efficient, widely applicable, and highly selective alpha-chlorination of simple silyl enolate with Lewis acid and an alpha,alpha-dichloro-1,3-dicarbonyl controller unit was reported. Diastereoselectivity and enantioselectivity of the reaction were investigated. High reactivity and selectivity were achieved by using alpha,alpha-dichlorinated malonic ester.     

Rapid racemization of chiral non-racemic sec-alcohols catalyzed by (η-C5(CH3)5)Ru complexes bearing tertiary phosphine-primary amine chelate ligands

A ternary catalyst system of Cp*RuCl(cod)-2-diphenylphosphinoethylamine-KOt-Bu (Cp*=η⁵-C₅(CH₃)₅, cod=1,5-cyclooctadiene) causes rapid racemization of chiral non-racemic sec-alcohols, which results from the reversible hydrogen transfer between sec-alcohols and ketones. Both tertiary phosphine and primary amine functionalities in the ligand are responsible for the high rate.     

Hepatoprotective and hepatotoxic actions of oleanolic acid-type triterpenoidal glucuronides on rat primary hepatocyte cultures

The protective effects of oleanolic acid-type saponins and their derivatives on in vitro immunological liver injury of primary cultured rat hepatocytes were studied. A known antihepatotoxic saponin (chikusetsusaponin IVa, 1) showed hepatoprotective activity in this model. Although a rhamnosyl derivative (2) of 1 similarly showed hepatoprotective activity, its prosapogenin (5) did not show any hepatoprotective activity. On the contrary, 5 exhibited cytotoxicity toward liver cells. In the absence of antiserum, monodesmosyl saponins showed hepatotoxicity, while the bisdesmosyl saponins except for 1, did not show such hepatotoxicity. In order to clarify the effects of the sugar residues at C-3 and C-28 responsible for hepatoprotective and hepatotoxic actions, oleanolic acid 3-O-glucuronide (2a) and oleanolic acid 28-O-glucoside (2b) were prepared and tested. 2b showed neither hepatoprotective action nor hepatotoxicity. In contrast, 2a was effective at 90 microM on hepatoprotection, although it showed strong hepatotoxicity. Oleanolic acid (2c) itself showed both hepatoprotective action and weak hepatotoxicity. Therefore, the hepatoprotective activity of these types of saponins could represent a balance between hepatoprotective action and hepatotoxicity.     

Theoretical designs of singlet localized 1,3-diradicals

Spin preference and S-T gaps of localized 1,3-diradicals were studied by an orbital phase theory and theoretical calculations. The orbital phase theory was applied to rationalize thermodynamic and kinetic stabilities of diradicals. We theoretically designed some singlet localized 1,3-diradicals, substituted trimethylenes, which are more stable than the lowest triplets. Some diradicals with the four-membered rings, 2,4-disilacyclobutane-1,3-diyls, were designed and shown to have singlet ground states and to be more stable than the sigma-bonded isomers, 2,4-disilabicyclo[1.1.0]butanes. The ab initio calculations supported predictions of the stable carbon-centered localized singlet 1,3-diradicals.     

Simultaneous determination of sulfamethoxazole and trimethoprim in human plasma by capillary zone electrophoresis

A capillary electrophoretic method for the simultaneous determination of sulfamethoxazole and trimethoprim in plasma was developed. Sulfamethoxazole and trimethoprim extracted from human plasma with ethyl acetate were analyzed at 20 kV and 25 degrees C using 15 mm phosphate buffer (pH 6.2) as the electrolyte. The detection was by UV at 220 nm. The run time was 8.0 min and the limit of quantification was 10.00 microg/mL for sulfamethoxazole and 2.00 microg/mL for trimethoprim. The recovery was >99% for both compounds. This method enabled the detection of sulfamethoxazole and trimethoprim in plasma of patients after oral ingestion of their combined formulation. The present simple and rapid method is applicable to drug monitoring in immunocompromised patients who are taking the combined formulation of these compounds for the treatment or prophylaxis of Pneumocystis carinii pneumonia.     

Direct UHV-TEM observation of palladium clusters on a silicon surface.

About 1 monolayer of palladium was deposited onto a silicon (111) 7 x 7 surface at a temperature of about 550 K inside an ultrahigh vacuum transmission electron microscope, resulting in formation of Pd2Si nanoislands and a 1 x 1 surface layer. Pd clusters created from an excess of Pd atoms on the 1 x 1 surface layer were directly observed by in situ plan view high-resolution transmission electron microscopy. When an objective aperture was introduced so that electron diffractions less than 0.20 nm were filtered out, the lattice structure of the 1 x 1 surface with 0.33 nm spacing and the Pd clusters with a trimer shape were visualized. It was found that image contrast of the 1 x 1 lattice on the specific height terraces disappeared, and thereby an atomic structure of the Pd clusters was clearly observed. The appearance and disappearance of the 1 x 1 lattice was explained by the effect of the kinematical diffraction. It was identified that a Pd cluster was composed of three Pd atoms without a centered Si atom, which is consistent with the model proposed previously. The feature of the Pd clusters stuck at the surface step was also described.