Tamao Odake

Liquid/Liquid Optical Waveguides Using Sheath Flow as a New Tool for Liquid/Liquid Interfacial Measurements

A liquid/liquid optical waveguide was constructed using a sheath flow. Since the refractive index of an organic solvent is generally higher than that of water (nD = 1.33), light introduced into the inner organic flow should proceed with total multi-reflection within the inner flow, so that the inner part of the sheath flow acts as the core of an optical waveguide. This sheath flow liquid/liquid optical waveguide was stable and showed no substantial background scattering. Moreover, it is applicable to both miscible and immiscible liquid/liquid interfaces. Thus, it may become a new tool for studying liquid/liquid interfaces as well as for sensitive optical measurements.

Sensitive measurement of methylene blue active substances by attenuated total reflection spectrometry with a trimethylsilane-modified glass slab optical waveguide

Attenuated total reflection spectrometry with a slab optical waveguide (SOWG) was explored for the simple, rapid and sensitive measurement of total anionic surfactants by the methylene blue active substance (MBAS) method. A fused-silica sheet used as a guiding layer was modified with trimethylsilane (TMS) to extract and concentrate the MBASs on the SOWG surface. Based on preliminary studies of the adsorption behavior and visible ATR spectrum of MB on the modified silica surface, a detection wavelength of 600 nm was chosen for the sensitive measurement of anionic surfactants. When the concentration of MB was set at 10 microM in the final measurement solution, the calibration curve for a typical anionic surfactant (sodium dodecylbenzenesulfonate) was linear up to 0.6 microM and the detection limit was 0.07 microM. The proposed method was applied to the determination of total anionic surfactants in river water.

Pulsed UV Laser-Induced Stationary Capillary Vibration for Highly Sensitive and Direct Detection of Capillary Electrophoresis.

A stationary wave of the capillary vibration effect was successfully induced by a series of short laser pulses. This wave could be applied to highly sensitive detection of capillary electrophoresis as well as the already reported capillary vibration induced by an intensity-modulated CW laser (CVL effect). Generally, pulses with much shorter width than the period of the natural frequency of the vibrating system cannot induce a standing vibration. However, utilizing the time constant of CVL determined by heat dissipation time, we found conditions which could induce a stable stationary wave of the capillary by a series of nanosecond light pulses. We used the KrF excimer laser operated at 248 nm with a pulse width of 60 ns and output of ∼10 μJ/pulse as the CVL excitation source and applied it to highly sensitive detection of nonderivatized amino acids at the femtomole level. The sensitivity was at least 2 orders of magnitude superior to that of a commercially available UV absorbance detector. This technique extends the CVLs spectral regions. For example, in the UV region, where many biological materials have significant absorption bands, this technique will extend analytical applications in capillary electrophoresis by eliminating the need for a derivatization process.

High-speed separation using miniaturized slab gel and high-spatial-resolution detection by a thermal lens microscope

Slab gel electrophoresis is a major tool for size-separation of DNA fragments and proteins. However, conventional slab gel electrophoresis uses a large gel to obtain sufficient separation and it takes several hours to separate, because conventional detectors using radio isotopes and fluorescence are affected by the strongly light-scattering gel and do not have enough spatial resolution to be applied to a miniaturized gel. Thermal lens microscope (TLM), which we have developed, has spatial resolution of micrometer level, and is not easily affected by the scattered light and can maintain high spatial resolution. We demonstrate here high- speed separation using a miniaturized gel and successive high spatial resolution detection using TLM. Using a miniaturized gel one-tenth of conventional gel in size, DNA fragments (100 base pair ladder sample) were separated in 5 to 15 minutes, which was about one order of magnitude faster than using a conventional gel, and successfully detected by TLM.

A sub-second, time-resolved, linear dichroism measurement system for visible attenuated total reflection spectroscopy with a slab optical waveguide.

A sub-second, time-resolved, linear dichroism (LD) measurement system was constructed, fitted with a slab optical waveguide (SOWG), and utilized to observe the adsorption process of methylene blue (MB) onto silica surfaces. In the system, a semiconductor laser (670nm) was used as the light source and the out-coupled beam from the SOWG was split by a polarizing beam splitter into two polarized beams (TE and TM modes) to allow sequential linear dichroic ratio data to be obtained; the acquisition rate was 11 data sets per second. For an MB solution that contained no sodium dodecylbenzenesulfonate (DBS), in contact with a bare silica surface, a clear decrease occurred in the average orientation angle of adsorbed MB in the initial stages of the adsorption process. This result may correspond to a change in the chemical form of MB from monomer to dimer.

Microfabricated Channels and Fluid Control Systems for Integrated Flow Injection Analysis

An integrated flow injection analysis (FIA) system on a glass chip has been achieved in the channels with various scales. It is intended that the channels of 10 to 200 μm wide are used for analytical chemistry and that those of less than 1 μm wide for physical chemistry. The channel of 200 μm wide and 100 μm deep is fabricated by CO2 laser cutting and thermally bonding. The isotropic wet etching with HF/NH4F is used for the channel with 30 μm wide and 10 μm deep. The etched Pyrex glass and the cover Pyrex glass are thermally bonded together. Further, the anisotropic dry etching such as reactive ion etching is performed for the channel with 1 μm wide and 1 μm deep. The etched Pyrex glass is anodically bonded to the Si wafer covered with silicon oxide film (800nm thick), which is consequently used as a cover glass. A new anisotropic etching technique using fast atom beam is carried out and the channel of 50 nm wide and 360 nm deep can be obtained. In all of the FIA systems, the chelating reaction of Fe(II) and o-phenanthroline has been realized.

Development of Liquid/Liquid Optical Waveguide Using a Two Phase Sheath Flow and Its Application to Fluorescent Determination of Rhodamine B

Proposed was the use of a sheath flow as a liquid/liquid optical waveguide, in which the inner flow works as core and the outer flow as clad. Firstly, the conditions to obtain a stable liquid/liquid optical waveguide were investigated: the stable waveguide was constructed with using toluene, diethyl eter and THF as an inner phase, which are miscible or immiscible with water. Furthermore, fluorescence spectra of rhodamine B excited by evanescent wave at the liquid/liquid interface of the waveguide were obtained and the effect of solvents on the fluorescent spectra was discussed.

Development of Tetrahydrofuran/Water Optical Waveguide and Its Application to the Observation of Extraction Behavior of 1-Anilino-8-naphtalene Sulfonate at the Tetrahydrofuran/Water Interface

A stable two-phase sheath flow using tetrahydrofuran (THF) for an inner flow and water for an outer flow was formed in a glass capillary, and worked as a stable liquid-core/liquid-cladding optical waveguide (THF/water LLW). Although THF and water were miscible with any ratio, the length of the stable THF/water LLW at 0.9 - 2.1 cm s-1 reached at least 150 mm. The THF/water LLW was applied to the observation of extraction behavior of solvatochromic fluorescence dye, 1-anilino-8-naphtalene sulfonate (ANS), through the THF/water interface. ANS was added to the water phase (clad solution) and its fluorescence, which was excited with the guided light (355 nm) through the LLW, was observed by changing the position of the detector. While the ANS stayed in the region of 70% THF to the end of the LLW without the addition of cationic surfactant, hexadecyltrimethylammonium ion (CTA+) at pH 3 and 11, the ion-pair of ANS and CTA+ was extracted into the higher concentration region of THF with the addition of CTA+ at pH 11.

Integration of Immunosorbent Assay System into a Multichannel Microchip for Clinical Diagnoses

The whole process of an immunosorbent assay system was integrated into a glass microchip. Analyte was adsorbed on polystyrene beads put in a microchannel, and then the antibody conjugated with colloidal gold was reacted. The colloidal gold bound to the beads was detected by a thermal lens microscope. By using a microchip with a multichannel system, simultaneous determination became possible. This system seems to be practically useful to clinical diagnosis. Moreover, troublesome operations required for the conventional immunosorbent assay were replaced by simple operations.

Photothermal Ultrasensitive Detection and Microchemistry in the Integrated Chemistry Lab

Non-fluorometric and non-electrophoretic lab-on-chip was realized with utilizing thermal lens microscopy for ultrasensitive detection and diffusion phenomenon for molecular transport. Thermal lens microscope, which was proved to be a determination method in single-molecule level, was applied to measure in submicron channels. Making the most of the micro space effects in liquids, diffusion phenomenon was shown to be very effectual driving force for molecular handling. Rapid mixing of two liquid phases and solvent extraction were achieved by molecular diffusion without any stirring or shaking. By integrating these chemical operation units, an on-chip chemistry lab was constructed to be applicable to wider uses than when electrophoretical driving force is the only means for transporting liquids. Chelating reaction, solvent extraction, and colorimetric determination of a metal ion in zmol levels were demonstrated.