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Author: search.filters.author.Motomizu, Shoji

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    A "dual-acceptor channel" membraneless gas-diffusion unit for simultaneous determination of ethanol and acetaldehyde in liquors using reverse flow injection
    (2018-01-01)
    Choengchan, Nathawut
    ;
    Poontong, Bangerdsuk
    ;
    Mathaweesansurn, Arjnarong
    ;
    Maneerat, Noppadol
    ;
    Motomizu, Shoji
    A new design of membraneless gas-diffusion unit with dual acceptor channels for separation, collection and simultaneous determination of two volatile analytes in liquid sample is presented. The unit is comprised of three parallel channels in a closed module. A sample is aspirated into the central channel and two kinds of reagents are introduced into the other two channels. Two analytes are isolated from the sample matrix by diffusion into head-space and absorbed into the specific reagents. Non-absorbed vapor is released by opening the programmable controlled lid. The unit was applied to liquors for measurement of ethanol and acetaldehyde using reverse flow injection. Dichromate and nitroprusside were exploited as reagents for colorimetric detection of ethanol and acetaldehyde, respectively. Good linearity ranges (r2 > 0.99) with high precision (RSD < 2%) and high accuracy (recovery: 90 - 105%) were achieved. The results were compared to the results by GC-FID and no significant difference was observed by paired t-test (95% confidence).
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    A low-cost method for determination of calcium carbonate in cement by membraneless vaporization with capacitively coupled contactless conductivity detection
    (2010-05-15)
    Sereenonchai, Kamonthip
    ;
    Teerasong, Saowapak
    ;
    Chan-Eam, Sumonmarn
    ;
    Saetear, Phoonthawee
    ;
    Choengchan, Nathawut
    This work presents a flow analysis method for direct quantitation of calcium carbonate in cement without pretreatment of the sample. The method is based on online vaporization of CO<inf>2</inf> gas following acidification of the sample inside a small chamber that has a flow of acceptor solution passing around it. Solubilization of the CO<inf>2</inf> gas into the acceptor stream changes the conductivity of the acceptor solution causing an increase of signal at the capacitively coupled contactless conductivity detection (C<sup>4</sup>D) placed at the outlet of the vaporization chamber. This chamber is an adaption from previous work reported on 'membraneless vaporization' (MBL-VP). The method can be used in the quality control of production of mixed cement. These cement materials usually have calcium carbonate contents at high concentration range (e.g., 33-99% (w/w) CaCO<inf>3</inf>). Analysis of samples by this method is direct and convenient as it requires no sample pretreatment. The method is low-cost with satisfactory accuracy and acceptable precision. © 2010 Elsevier B.V.
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    Quality control of gasohol using a micro-unit for membraneless gas diffusion
    (2009-01-01)
    Muncharoen, Sasithorn
    ;
    Sitanurak, Jirayu
    ;
    Tiyapongpattana, Warawut
    ;
    Choengchan, Nathawut
    ;
    Ratanawimarnwong, Nuanlaor
    This work describes the development of a new spectrophotometric flow technique suitable for monitoring of ethanol content in gasohol fuel. Membraneless gas-diffusion (MBL-GD) was applied with one-step aqueous extraction of gasohol (1:2 gasohol/water). Segments of aqueous extract and color developing reagent were allowed to flow into two separate channels in the MBL-GD device. Inside the device, ethanol vapor can diffuse across a small headspace between the two channels (donor and acceptor). Introduction of an air-segment behind the zone of acceptor reagent to stop dispersion of the colored zone greatly improves the rapidity of analysis using this MBL-GD technique. Two methods were developed for quality control of gasohol by measuring ethanol content. Method I is suitable for direct calibration of E5 and E10. Method II is recommended for E20. These methods have high accuracy with good precision (% RSD: 1 to 4.9, n=45) and have a sample throughput of 26 samples per hour. E10 samples were compared with analysis using a standard GC method. © 2008 Springer-Verlag.
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