Nobuhiro Ishio
Kobe University
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Publication
Featured researches published by Nobuhiro Ishio.
Electrophoresis | 2002
Keiichi Fukushi; Takashi Miyado; Nobuhiro Ishio; Hideaki Nishio; Keiitsu Saito; Sahori Takeda; Shin-ichi Wakida
We describe a combination of selected ions as a terminating ion which is useful for transient isotachophoresis (ITP) in capillary zone electrophoresis (CZE) for the determination of nitrite and nitrate in seawater. In addition to 150 mM sulfate as the principal terminating ion, 10 mM bromate was added to a sample solution as the additional terminating ion. Artificial seawater containing 3 mM cetyltrimethylammonium chloride (CTAC) was adopted as a background electrolyte (BGE). The limits of detection (LODs) for nitrite and nitrate were 2.2 and 1.0 νg/L (as nitrogen), respectively. The LODs were obtained at a signal to noise ratio (S/N) of 3. The values of the relative standard deviation (RSD) of peak area for these ions were 1.9 and 1.4%. The RSDs of peak height were 1.7 and 1.9%, the RSDs of migration time 0.11%. The proposed method was applied to the determination of nitrite and nitrate in a proposed certified reference material for nutrients in seawater, MOOS‐1, distributed by the National Research Council of Canada (NRC). The results almost agreed with the assigned tolerance interval.
Journal of Chromatography A | 2000
Andrei R. Timerbaev; Keiichi Fukushi; Takashi Miyado; Nobuhiro Ishio; Keiitsu Saito; Shoji Motomizu
The ability to analyze samples with disparate levels of analyte and matrix ions is among the important benefits defining the practical utility of modern capillary electrophoresis. To compensate for the sensitivity limitations regarding trace-level inorganic anions, a number of on-line approaches that should offer an improved S/N ratio in direct UV detection were examined. The novel use of reversed pre-electrophoresis (at the applied voltage opposite to the separation voltage) made it possible to efficiently remove the most part of high chloride levels from the sample and hence to lower the background signal and to inject increased quantities of fast analyte anions. Specifically, by taking these advantages the sensitivity response of iodide was improved by a factor of 5 over normal CE mode. Using isotachophoretic sample stacking, a two-fold increase in detectability was obtained for moderately mobile anions, nitrate and nitrite, that corresponds to the minimum detectable concentrations close to their natural occurrences in seawater. Furthermore, field-amplified sample injection at increased electrolyte-to-sample matrix concentration ratios enabled the maximum S/N enhancement, with detection limits at the level of 10(-6) M and lower in the presence of > or = 5 x 10(4)-fold molar excess of chloride.
Electrophoresis | 2000
Keiichi Fukushi; Nobuhiro Ishio; Makoto Sumida; Sahori Takeda; Shin-ichi Wakida; Kazuo Hiiro
We describe capillary zone electrophoresis (CZE) with transient isotachophoresis (ITP) for the determination of low concentrations of nitrite and nitrate ions in seawater. Bromide‐free artificial seawater was adopted as background electrolyte (BGE) to eliminate the interference of high concentrations of salts in seawater. To reverse the electroosmotic flow (EOF), 3 mM cetyltrimethylammonium chloride (CTAC) was added to the BGE. High concentrations of chlorate were added to sample solutions as the terminating ion to generate the ITP process before the CZE separation. In general, the stacking effect increased with increasing amounts of chlorate injected into the capillary. The limits of detection (LODs) for nitrite and nitrate were 0.063 and 0.033 mg/L when the chlorate concentration was 600 and 200 mM, respectively; these were half of those obtained by CZE without the transient ITP. The LODs were obtained at a signal to noise ratio (S/N) of 3. The relative standard deviations (RSD, n = 10) of the peak areas for these ions were 3.2 and 2.9%. The RSDs of peak heights for these ions were 1.6 and 2.1%. The RSDs of migration times for these ions were 0.67 and 0.46%.
Journal of Electroanalytical Chemistry | 1998
Sadayuki Himeno; Nobuhiro Ishio
Abstract The formation processes of V(V)- and V(IV)-substituted molybdophosphate complexes with the Keggin structure were studied by a combined redox and ion-transfer voltammetric study. There was a big difference in the formation processes between V(V)- and V(IV)-substituted mixed complexes in aqueous solution. The Mo(VI)+P(V)+V(IV) system produced a blue mixed complex in which the peripheral Mo atoms possessed the oxidation number of VI; only a mono-substituted complex was formed even in the presence of excess of V(IV). In the Mo(VI)+P(V)+V(V) system, on the other hand, evidence was obtained for the spontaneous transformation of a mono-substituted complex into mixed complexes with higher V(V) contents.
Electrophoresis | 2000
Keiichi Fukushi; Nobuhiro Ishio; Hideo Urayama; Sahori Takeda; Shin-ichi Wakida; Kazuo Hiiro
We describe capillary zone electrophoresis (CZE) for the simultaneous determination of bromide, nitrite and nitrate ions in seawater. Artificial seawater was adopted as the carrier solution to eliminate the interference of high concentrations of salts in seawater. The artificial seawater was free from bromide ion to enable the determination of bromide ion in a sample solution. For the purpose of reversing the electroosmotic flow (EOF), 3 mM cetyltrimethylammonium chloride (CTAC) was added to the carrier solution. A 100 μm ID (inside diameter) capillary was used to extend the optical path length. The limits of detection (LODs) for bromide, nitrite, and nitrate ions were 0.46, 0.072, and 0.042 mg/L (as nitrogen), respectively. The LODs were obtained at a signal to noise ratio (S/N) of 3. The values of the relative standard deviation (RSD) of peak area for these ions were 1.1, 1.5, and 0.97%. The RSDs of migration time for these ions were 0.61, 0.69, and 0.66%. Artificial seawater samples containing various concentrations of bromide, nitrite, and nitrate ions were analyzed by the method. The error was less than ±12% even if the concentration ratio of bromide ion to nitrite or nitrate ion was 20—240. The proposed method was applied to the determination of bromide, nitrite, and nitrate ions in seawater samples taken from the surface and the seabed. These ions in other environmental waters such as river water and rainwater samples were also determined by ion chromatography (IC) as well as this method.
Analytical Communications | 1999
Keiichi Fukushi; Nobuhiro Ishio; Kazuo Hiiro
This paper demonstrates the potential contribution to the environment from water soluble phosphorus contained in discarded tobacco products. Dry tobacco was soaked in water and the concentration of dissolved phosphorus was determined by absorptiometry and ion chromatography. The total phosphorus was also measured by absorptiometry following decomposition by a nitric–sulfuric acid decomposition method. As a result, it was found that ca. 1.2 mg of phosphorus (as total PO4-P) was dissolved from unit mass of dry tobacco. It is estimated that the amount of phosphorus that could pass into the Japanese environment through discarded cigarettes was 115–208 kg per day.
Electrophoresis | 2003
Kuriko Yokota; Keiichi Fukushi; Nobuhiro Ishio; Nobukazu Sasayama; Yusuke Nakayama; Sahori Takeda; Shin-ichi Wakida
Analytical and Bioanalytical Chemistry | 2002
Nobuhiro Ishio; Keiichi Fukushi; Kanako Michiba; Sahori Takeda; Shin-ichi Wakida
Bunseki Kagaku | 2005
Keiichi Fukushi; Kuriko Yokota; Yusuke Nakayama; Nobuhiro Ishio; Takashi Miyado
Bulletin of the Society of Sea Water Science, Japan | 2004
Keiichi Fukushi; Nobuhiro Ishio; Jun-ichi Tsujimoto; Kuriko Yokota; Terunobu Hamatake; Hiroya Sogabe; Ken-ichi Toriya; Tsukimi Ninomiya
Collaboration
Dive into the Nobuhiro Ishio's collaboration.
National Institute of Advanced Industrial Science and Technology
View shared research outputsNational Institute of Advanced Industrial Science and Technology
View shared research outputsNational Institute of Advanced Industrial Science and Technology
View shared research outputsNational Institute of Advanced Industrial Science and Technology
View shared research outputs