start-ver=1.4
cd-journal=joma
no-vol=17
cd-vols=
no-issue=11
article-no=
start-page=1285
end-page=1290
dt-received=
dt-revised=
dt-accepted=
dt-pub-year=2001
dt-pub=20011110
dt-online=
en-article=
kn-article=
en-subject=
kn-subject=
en-title=
kn-title=Highly Sensitive Determination Method for Total Carbonate in Water Samples by Flow Injection Analysis Coupled with Gas-Diffusion Separation
en-subtitle=
kn-subtitle=
en-abstract=
kn-abstract=A spectrophotometric method for the determination of total carbonate in water samples was developed. The method is based on the color change of an acid-base indicator in relation to the concentration of permeable gas substances through a membrane. By using a new portable FIA system equipped with a gas-diffusion unit, a highly sensitive and on-site determination of total carbonate in aqueous solutions was investigated. A new color-change system with 4-(2',4'-dinitrophenylazo)-1-naphthol-5-sulfonic acid (DNN5S) was developed. Absorbance changes of the reagent solution were measured at 450 nm with a light-emitting diode (LED) as a light source. A new type of gas-diffusion unit was used, and was constructed with double tubing: the inner tubing was a micro porous PTFE (polytetrafluoroethylene) tubing (1.0 mm inner diameter and 1.8 mm outer diameter, pore size 2 ƒÊm, porosity 50%); the outer tubing was made of glass with 2.0 mm inner diameter. The optimized system conditions were as follows: the sample size was 200 ƒÊl, the temperature of the air bath for the gas-diffusion unit was 25�Ž, and the length of the gas-diffusion unit was 15 cm; each flow rate was 0.3 ml min(-1). For measuring carbonate at low concentrations, a method for preparing water with less carbonate was proposed: the carbonate content of the water was decreased down to 5�~10(-7) M. The calibration graph was rectilinear from 1�~10(-6) M to 10(-3) M, and the detection limit (corresponding to a signal-to-noise ratio of 3) was 1�~10(-6) M of carbonate. The relative standard deviation (RSD) of ten measurements of 2.3�~10(-5) M Na(2)CO(3) solution was 1.9%. The total carbonate in various kinds of water (such as river, sea, rain, distilled and ultra purified) was determined.
en-copyright=
kn-copyright=

en-aut-name=OshimaMitsuko
en-aut-sei=Oshima
en-aut-mei=Mitsuko
kn-aut-name=‘哇ŒõŽq
kn-aut-sei=‘哇
kn-aut-mei=ŒõŽq
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ORCID=

en-aut-name=WeiYanlin
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en-aut-mei=Yanlin
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en-aut-name=YamamotoMasaki
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en-aut-mei=Masaki
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en-aut-name=TanakaHiroki
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en-aut-name=MotomizuShoji
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END