Micro Emission Ltd.

Nomi, Japan

Micro Emission Ltd.

Nomi, Japan

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Hung N.T.,Institute for Technology of Radioactive and Rare Elements ITRRE | Thuan L.B.,Institute for Technology of Radioactive and Rare Elements ITRRE | Van Khoai D.,Micro Emission Ltd. | Lee J.-Y.,Korea Institute of Geoscience and Mineral Resources | Jyothi R.K.,Korea Institute of Geoscience and Mineral Resources
Journal of Nuclear Materials | Year: 2016

Uranium dioxide (UO2) powder has been widely used to prepare fuel pellets for commercial light water nuclear reactors. Among typical characteristics of the powder, specific surface area (SSA) is one of the most important parameter that determines the sintering ability of UO2 powder. This paper built up a mathematical model describing the effect of the fabrication parameters on SSA of UO2 powders. To the best of our knowledge, the Brandon model is used for the first time to describe the relationship between the essential fabrication parameters [reduction temperature (TR), calcination temperature (TC), calcination time (tC) and reduction time (tR)] and SSA of the obtained UO2 powder product. The proposed model was tested with Wilcoxon's rank sum test, showing a good agreement with the experimental parameters. The proposed model can be used to predict and control the SSA of UO2 powder. © 2016 Elsevier B.V. All rights reserved.


Do V.K.,Japan Advanced Institute of Science and Technology | Yamamoto T.,Micro Emission Ltd | Ukita Y.,Yamanashi University | Takamura Y.,Japan Advanced Institute of Science and Technology
Sensors and Actuators, B: Chemical | Year: 2015

Liquid electrode plasma (LEP) optical emission spectrometry (OES) is a novel elemental analysis method that utilizes discharged microplasma in a liquid sample as an excitation source to detect metal ions. LEP-OES has been commercialized as a handy device that uses disposable microfluidic chips. To improve the sensitivity, integration of a solid phase extraction (SPE) column into the LEP chip as preconcentrator was proposed with the use of an external syringe pump for fluid actuation. However, poor control of the external pump at low pumping volumes and high back-pressures caused poor analytical performance of the integrated system. In this study, a simply designed internal pneumatic injection pump was redeveloped and employed as a fluid actuator. The internal pump can be easily operated by an automated pneumatic pressure controller and is capable of injecting a reproducible amount of eluent for each measurement cycle of SPE-LEP. Additionally, the pump acted as a valve to stop the backflow caused by the high pressure created by plasma generation. More precise flow control by the internal pump helped improve the precision of the measurements. For data processing, exponentially modified Gaussian model was utilized to describe the elution peaks. The limit of detection for lead (0.4. ng/mL) was 50 times improved in comparison with conventional LEP. The proposed method and data processing model can be used to develop on-chip detection applications for methods that utilize pulsed microplasma sources. © 2015 Elsevier B.V.


Van Khoai D.,Japan Advanced Institute of Science and Technology | Yamamoto T.,Micro Emission Ltd. | Ukita Y.,Japan Advanced Institute of Science and Technology | Takamura Y.,Japan Advanced Institute of Science and Technology
17th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2013 | Year: 2013

In this paper we report the improvement of sensitivity for liquid electrode plasma atomic emission spectrometry (LEP- AES) by combination with solid phase extraction (SPE) and constant volume pneumatic membrane micropump. The micropump can provide a steady volume of liquid for elution process of SPE, enabling us to reduce eluent more reliably and/or to use the analyte more effectively. The chip can detect Pb of 10 ng (1 ppb with 10 mL sample and 10 ppb with 1 mL sample). Copyright © (2013) by the Chemical and Biological Microsystems Society All rights reserved.


Khoai D.V.,Japan Advanced Institute of Science and Technology | Yamamoto T.,Micro Emission Ltd. | Ukita Y.,Japan Advanced Institute of Science and Technology | Takamura Y.,Japan Advanced Institute of Science and Technology
Japanese Journal of Applied Physics | Year: 2014

This paper reports the application of liquid electrode plasma atomic emission spectrometry (LEP AES) integrated with on-chip solid phase extraction (SPE) for determination of lead (Pb). LEP AES is a novel elemental analysis method employing micro-plasma in the sample solution as excitation source. The integration of SPE to LEP chip shows high potential of application with several merits because on-chip SPE enables the effective use of sample. In the work an improved LEP chip integrated with SPE was developed for trace lead detection. Chip design and pulse voltage were proposed to eliminate the ash generation and minimize the channel expansion. Some analytical parameters were optimized. With sample volume of 1 mL calibration curve in the range of 0-100ng/mL the correlation coefficient of 0.992 and limit of detection (LOD) of 0.64ng/mL were obtained. With the support of SPE, LOD was improved about 30 times. © 2014 The Japan Society of Applied Physics.


Nakayama K.,Micro Emission Ltd. | Yamamoto T.,Micro Emission Ltd. | Hata N.,University of Toyama | Taguchi S.,University of Toyama | Takamura Y.,Japan Advanced Institute of Science and Technology
Bunseki Kagaku | Year: 2011

Liquid electrode plasma atomic emission spectrometry (LEP-AES) is a compact elemental-analysis method, which requires no plasma gas and no high-power source, and is suitable for on-site portable analysis. In this paper, the LEP-AES is combined with the concentration method using liquid organic ion associate extraction, and a concentration/simultaneous determination method for trace metals (Cu, Mn, Pd, Zn, Cd and Pb) in water is developed. Metals were converted into a complex with a chelating reagent in a 40 mL sample solution, and were extracted into a liquid ion associate during phase formation. The volume of the ion associate was μL-scale. The ion associate was dissolved with 400 μ L of a 50 vol% methanol + 0.1 M HNO3 solution, followed by detection by LEP-AES using 40 μLL of the sample. As a results, a liquid organic ion associate extraction enabled a 100-fold enrichment of trace metals, and improved the detection limits (3 σ) by a few μL L-1 - sub mg L-1 Interestingly, for some metal elements, the magnification of the total sensitivity combined with LEP-AES resulted in more than 1000, which is more than the value of 100-fold for the enrichment. This method was applied to the determinations of Cu, Mn, Zn, Cd and Pb in certified reference materials (EnviroMAT EU-H-1 waste water). The values obtained in this method were nearly equal to the certified values. © 2011 The Japan Society for Analytical Chemistry.


Van Khoai D.,Japan Advanced Institute of Science and Technology | Kitano A.,Japan Advanced Institute of Science and Technology | Yamamoto T.,Micro Emission Ltd. | Ukita Y.,Japan Advanced Institute of Science and Technology | Takamura Y.,Japan Advanced Institute of Science and Technology
Microelectronic Engineering | Year: 2013

Liquid electrode plasma - Atomic emission spectrometry (LEP-AES) is a novel elemental analysis method where a liquid sample is filled in a micro channel that has a narrow part at the center. High voltage is applied to the solution at the both ends of the channel, and consequently microplasma is generated in the channel. The microplasma is an excitation source for atomic emission spectrometry. The method is suitable for heavy metal detection. In this work, to improve detection limit, we integrated a solid phase extraction (SPE) column on a liquid electrode plasma chip (LEP chip) to improve the sensitivity of this method for lead (Pb) detection. The chip design and flow control technique was proposed based on the point of reducing the necessary eluent for one measurement. Chip pattern was made by Polydimethylsiloxane (PDMS) employing negative photolithography. The integrated chip was successful in detecting 10 ppb Pb in solution. Detection limit for Pb of LEP method is improved. © 2013 Elsevier B.V. All rights reserved.


Kohara Y.,Hitachi Ltd. | Terui Y.,Hitachi High-Technologies | Ichikawa M.,Hitachi High-Technologies | Yamamoto K.,HIGH-TECH | And 4 more authors.
Journal of Analytical Atomic Spectrometry | Year: 2015

Liquid electrode plasma atomic emission spectrometry (LEP-AES) is a new elemental analysis method that uses microplasma. LEP forms in a vapor bubble generated inside a narrow-center microchannel by using high-voltage DC pulse power. In this study, we used a novel hourglass microchannel having a 3-dimensionally and axisymmetrically narrowed shape, which caused a bright emission roughly 200 times that of the flat microchannel used in our previous study. We observed the spatial distribution of atomic emission and determined the limit of detection (LoD) by utilizing the confirmed spatial distribution. We found that the spatial distribution of atomic emission for 41 elements in our experiments could be classified into three patterns in accordance with a maximum emission point: anode side, narrow-center, and cathode side. Atomic emission was measured at the maximum emission point and the calibration curve for each element was made to determine the LoD. The LoD of 25 tested elements in our experiment ranged from 1 μg L-1 for Li to 306 μg L-1 for V. © The Royal Society of Chemistry 2015.


Kohara Y.,Hitachi Ltd. | Terui Y.,Hitachi High-Technologies | Ichikawa M.,Hitachi High-Technologies | Shirasaki T.,Hitachi High-Technologies | And 3 more authors.
Journal of Analytical Atomic Spectrometry | Year: 2012

Liquid electrode plasma atomic emission spectrometry (LEP-AES) is a recently developed elemental analysis method that uses microplasma. LEP forms in a vapor bubble generated inside a narrow-center microchannel by using high-voltage DC pulse power. We studied the characteristics of LEP and atomic emission of lead (Pb), as an example element, which has not been described in detail. We estimated the plasma parameters and observed the expansion and shrinkage of a vapor bubble with discharge as well as the time course and spatial distribution of the atomic emission of Pb (405.78 nm). The applied voltage was 2.5 kV and the pulse width was less than 3 ms, which produced a current of about 100 mA. We found that the excitation temperature was about 8000 K and the electron density was about 1 × 10 15 cm -3. We also found that two quite different emission phases occurred separately during the time course. The first emission phase corresponds to the first expansion and shrinking of the bubble around atmospheric pressure and the second emission phase corresponds to the re-expansion of the bubble and emission at reduced pressure with higher atomic and lower background emissions. Maximum atomic and background emissions were observed at the narrowed center of the microchannel, but there was an additional local maximum atomic emission region at the anode side bubble-liquid interface where the background emission was very low, which would be a better condition for sensitive measurement. The limit of detection determined in our experiment was 4.0 μg L -1 for Pb. © 2012 The Royal Society of Chemistry.


Kagaya S.,University of Toyama | Nakada S.,University of Toyama | Inoue Y.,Nippon Filcon Co. | Kamichatani W.,Nippon Filcon Co. | And 5 more authors.
Analytical Sciences | Year: 2010

Solid phase extraction using a mini cartridge packed with 22 mg of chelate resin immobilizing carboxymethylated pentaethylenehexamine was successfully utilized for separation/preconcentration of cadmium in water samples prior to liquid electrode plasma atomic emission spectrometric (LEP-AES) determination. The combined method with the extraction and LEP-AES was applicable to the determination of cadmium in the certified reference materials (EU-L-1 wastewater and ES-L-1 groundwater); the detection limit was 0.20 μg in 200 mL of sample solution (500-fold preconcentration). 2010 © The Japan Society for Analytical Chemistry.


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Micro Emission Ltd. | Date: 2016-03-15

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