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Takashi Korenaga

Publications and source records attributed to Takashi Korenaga.

14 recordsLinked to original sources
PubMed2006

Application of a monolithic silica capillary adsorbent for the preconcentration of airborne trichloroethylene and tetrachloroethylene.

Monolithic silica with a bimodal pore structure was prepared in a fused silica capillary by the sol-gel process and investigated as an adsorbent for the preconcentration of airborne trichloroethylene and tetrachloroethylene. The airborne trichloroethylene and tetrachloroethylene are adsorbed when they flow through the silica capillary column and can be desorbed by liquid hexane followed by GC/MS analysis. The monolithic silica adsorbent is mechanically stable and no frits or other special structures are needed to retain them in place. In addition, owing to the smaller size of the capillary column, only a small volume of desorption solvent is needed. The present investigation demonstrates the satisfactory applicability of monolithic silica as a capillary adsorbent.

Adsorption↗
PubMed2006

Development and optimization of a lab-on-a-chip device for the measurement of trace nitrogen dioxide gas in the atmosphere.

We propose the use of lab-on-a-chip technology for measuring gaseous chemical pollutants, and describe the development of a microchip for the detection of nitrogen dioxide (NO2) in air. A microchip fabricated from quartz glass has been developed for handling the following three functions, gas absorption, chemical reaction and fluorescence detection. Channels constructed in the microchip were covered with porous glass plates, allowing nitrogen dioxide to penetrate into the triethanolamine (TEA) flowing within the microchannel beneath. The nitrogen dioxide was then mixed with TEA and reacted with a suitable fluorescence reagent in the chemical reaction chamber in the microchip. The reacted solution was then allowed to flow into the fluorescence detection area to be excited by an ultraviolet light-emitting diode (UV-LED), and the fluorescence was detected using a photomultiplier tube (PMT). The reaction time, reagent concentration, pH, flow rate and other measurement conditions were optimised for analysis of nitrogen dioxide in air. Preliminary studies with standardized test solutions revealed quantitative measurements of nitrite ion (NO2-), which corresponded to atmospheric nitrogen dioxide in the range of 10-80 ppbv.

Air Pollutants↗
PubMed2006

Integration of the cleanup process: pretreatment of polycyclic aromatic hydrocarbons from diesel exhaust particles on silica gel beads in a microchannel.

This paper presents an integrated microfluidic system that performs cleanup for polycyclic aromatic hydrocarbons (PAHs) from diesel exhaust particles on silica gel beads in a microchip. A column chromatography phase was constructed by filling the silica gel beads into a microchannel that had a dam structure 25 microm high. The height of the dam structure was determined according to the rate of the wet etching. This work on the cleanup of PAHs from diesel exhaust particles showed that the microchip-based system has the same performance as the conventional method on the solid phase extraction column and has some advantages, such as less reagent consumption and shorter pretreatment time, over the conventional method.

Journal Article↗
PubMed2006

Novel method to identify illegal diesel fuel, I: use of adamantane or [1, 2-D2] n-tetradecane as chemical marker.

In this study, we demonstrated a new identification method of illegal diesel fuel using adamantane (tricyclo[3,3,1,1,(3,7)]decane) or [1, 2-D(2)] n-tetradecane as a potential chemical marker instead of coumarin. In a mixing system of diesel fuel with marker-labeled kerosene, the concentration of kerosene in the mixed oil is quantitatively determined using specific ion fragments of the markers using GC/MS analysis, in which the detection limit is 12.5 ng/microl for adamantane or 7.1 ng/microl for [1, 2-D(2)] n-tetradecane. Coumarin, the currently used chemical marker, can be easily removed by sulfuric acid treatment, which is a primal cause of environmental pollution due to the illicit disposal of the strong acidic by-product. However, adamantane and [1, 2-D(2)] n-tetradecane cannot be removed by sulfuric acid treatment. Thus, although the detection limit of adamantane and [1, 2-D(2)] n-tetradecane is higher by approximately one or two orders of magnitude than that of coumarin, they cannot be removed by sulfuric acid treatment. Therefore, adamantane and [1, 2-D(2)] n-tetradecane are strong candidates as potential markers instead of coumarin, leading to the prevention of the production of illegal diesel fuel and a reduction in environmental pollution.

Adamantane↗
PubMed2006

A simple fluorometric method for the determination of sulfur dioxide in ambient air with a passive sampler.

A simple and rapid fluorescence detection method was used for the determination of sulfur dioxide (SO(2)) in ambient air collected by a passive sampler. Gaseous SO(2) was absorbed as sulfite ions into an absorbing solution of triethanolamine (TEA) contained in an adsorbent sheet and reacted with N-(9-acridinyl)maleimide (NAM), which was used as a fluorescent reagent. TEA was also used as a buffer solution in this study. The calibration curve of SO(2) showed a linear correlation R(2)=0.992, and the relative standard deviation (RSD) was 2.4% for 50 ppb SO(2) with six repeated measurements. It was satisfactory to apply this method to determine the SO(2) level for simultaneous multipoint monitoring.

Air Pollutants↗
PubMed2006

Effect of aspect ratio on chemical reactions on microchip.

Parallel two-phase laminar flow, which is formed when two solutions flow in microchannels, has been developed and has advanced unique research in the area of microchip analysis. In two-phase laminar flow, channel size has a significant effect on the efficiency of chemical reactions. However, the sizes of microchannels vary greatly in many studies. In this paper, we report on the effect of microchannel size on chemical reactions on a microchip. Aspect ratio is defined as the ratio of depth to width of a microchannel. Five microchips with different aspect ratios (from 0.50 to 2.00) were fabricated by mechanical machining. The reaction of nitrous acid and Saltzman reagent was carried out on these microchips and the absorbance was measured on-line in a capillary tube, which was attached to the outlet on the microchip. The results showed that the color reaction occurred more efficiently as the aspect ratio increased. This result is expected to be useful when determining the size of microchannels.

Ethylenediamines↗
PubMed2006

Characterization of hydrophilic polymer fine particles by steady-state fluorescence spectroscopy.

We synthesized hydrophilic polymer particles based on acrylamide, and their chemical properties are investigated by fluorescence spectroscopy. The morphology of the synthesized polymers was monitored by scanning electron microscopy (SEM) and a dynamic light-scattering analyzer, and it was observed that the synthesized polymers are spherical with a median diameter of approximately 500 nm. A fluorescent probe molecule (C153) was introduced into the polymer/water solution, and the steady-state fluorescence spectrum was observed. In the C153/polymer/water solution, strong fluorescence inHtensity from the C153 molecules was observed with a maximum intensity at 515 nm, whereas the C153/water solution only gave very weak fluorescence with a maximum at 540 nm. Since C153 is hardly soluble in water, it was concluded that the C153 molecules existed selectively around the particle surfaces. Because of the difference between the fluorescence spectra, it was found that the chemical properties around the polymer surface were very different from that of the bulk water.

Microscopy, Electron, Scanning↗
PubMed2005

Development of a micro dual beam fluorometric detector specific for microchip analysis of benzo[a]pyrene and benzo[k]fluoranthene in diesel exhaust particulate samples.

We developed a device and some systems for detecting benzo[a]pyrene (B[a]P) and benzo[k]fluoranthene (B[k]F). The device uses a UV light-emitting diode that emits light with a wavelength of 370 nm and a violet laser diode that emits light with a wavelength of 395 nm as excitation light sources. The detection method is based on the following observation: characteristic fluorescence is emitted from both B[a]P and B[k]F, with intensities up to 10 times greater than those from 22 other polycyclic aromatic hydrocarbons (PAHs). The excitation and emission wavelengths for fluorescence from B[a]P and B[k]F are 370 and 429 nm, and 395 and 429 nm, respectively. Further, we calculated their concentrations in diesel exhaust particles by means of two calibration curves determined using a mixture of 24 PAHs. The detection limits of the proposed device with a microchip are 5.58 microg L(-1) for B[a]P and 6.03 microg L(-1) for B[k]F. We applied this method to analyze B[a]P or B[k]F contained in three types of diesel exhaust particles, and the results agreed well with those obtained by liquid chromatography.

Benzo(a)pyrene↗
PubMed2005

Design and synthesis of glycosidase inhibitor 5-amino-1,2,3,4-cyclohexanetetrol derivatives from (-)-vibo-quercitol.

In continuation of development of bioactive inositol derivatives, a 1-O-methyl derivative of 5-amino-5-deoxy-L-talo-quercitol was designed and synthesized as an analogue of the strong alpha-fucosidase inhibitor, 5a-carba-alpha-L-fucopyranosylamine, the methyl branch being replaced with methoxyl, and demonstrated to be a moderate alpha-fucosidase inhibitor. The present approach provides a possible route to apply alkyl ethers of aminodeoxyinositols as hexopyranose mimics of biological interest.

Animals↗
PubMed2005

Laser-induced fluorescence microscopic system using an optical parametric oscillator for tunable detection in microchip analysis.

A laser-induced fluorescence microscopic system based on optical parametric oscillation has been constructed as a tunable detector for microchip analysis. The detection limit of sulforhodamine B (Ex. 520 nm, Em. 570 nm) was 0.2 mumol, which was approximately eight orders of magnitude better than with a conventional fluorophotometer. The system was applied to the determination of fluorescence-labeled DNA (Ex. 494 nm, Em. 519 nm) in a microchannel and the detection limit reached a single molecule. These results showed the feasibility of this system as a highly sensitive and tunable fluorescence detector for microchip analysis.

Bacteriophage lambda↗
PubMed2004

Synthesis and glycosidase inhibitory activity of some N-substituted 5a-carba-beta-fuco- and beta-galactopyranosylamines, and selected derivatives.

In the course of chemical modification of alpha-fucosidase inhibitors of 5a-carba-fucopyranosylamine type, an N-dodecyl derivative of the enantiomer 6-deoxy-5a-carba-beta-D-galactopyranosylamine demonstrated very strong inhibition of beta-galactosidase and beta-glucosidase. This finding led us to synthesize corresponding 6-hydroxy compounds, in order to elucidate structure-activity relationships for inhibitors of this type. Among four N-alkyl-5a-carba-beta-D-galactopyranosylamines prepared, the N-octyl derivative could be demonstrated to possess moderate activity toward alpha- and beta-galactosidases, and beta-glucosidase.

Galactosamine↗
PubMed2004

Convenient synthesis and evaluation of glycosidase inhibitory activity of alpha- and beta-galactose-type valienamines, and some N-alkyl derivatives.

Valienamine analogues having alpha- and beta-galactose-type structures were synthesized by racemic modification from (1SR,2RS,3SR)-6-methylenecyclohex-4-ene-1,2,3-triol. Four N-alkyl derivatives of the beta-anomer were readily prepared selectively by treatment of key intermediate 2,6-di-O-acetyl-3,4-O-isopropylidene-5a-carba-alpha- and beta-l-arabino-hex-5(5a)-enopyranosyl bromides with alkyl amines. All compounds were assayed for inhibitory activity against six glycosidases, and the N-dodecyl derivative was shown to be a very strong inhibitor of beta-galactosidase (IC(50) 0.01 microM, bovine liver).

Animals↗