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Shunitz Tanaka - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical immunoassay at a 17β-estradiol self-assembled monolayer Electrode using a redox marker
The Analyst, 2003Co-Authors: Hideki Kuramitz, Kazuharu Sugawara, Mari Matsuda, Jennifer H. Thomas, Shunitz TanakaAbstract:A simple electrochemical immunoassay was demonstrated using a 17β-estradiol modified Electrode. 17β-estradiol was immobilized on the gold Electrode surface with a self-assembly technique. The specific binding between estradiol antibody and 17β-estradiol on the Electrode surface was evaluated by monitoring the change in the Electrode Response with three hydrophilic redox markers. The decrease in the Electrode Response for the redox marker was observed, when the antibody was bound to the estradiol self-assembled monolayer (SAM) Electrode surface. The change in the Electrode Response of the redox marker is attributed to the steric hindrance between the antibody on the Electrode surface and the redox marker. The relative standard deviation at 30 μg ml−1 estradiol antibody was 4.1% (n = 3). The competitive reaction between the antigen in the solution and 17β-estradiol immobilized on the Electrode surface for the limited binding sites on the antibody produced an increase in the Electrode Response with hydroquinone as the marker. The binding affinity of three antigens including 17β-estradiol to the estradiol antibody was evaluated. Furthermore, the result obtained from this method was compared with the previously reported enzyme binding assay using the biotinylated estradiol and the biotin-immobilized microtiter plate.
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Electrochemical Evaluation of the Interaction between Avidin and Biotin at Biotinylated Polypyrrole Electrode Using a Redox Marker
Electroanalysis, 2003Co-Authors: Hideki Kuramitz, Kazuharu Sugawara, Mari Matsuda, Shunitz TanakaAbstract:The interaction between avidin and biotin was evaluated electrochemically by monitoring the change in the Electrode Response of redox markers. Biotin was immobilized on the Electrode surface by means of the electrochemical polymerization of biotinylated pyrrole and pyrrole. When avidin was introduced onto the biotinylated polypyrrole Electrode surface, the large change in the Electrode Response of the redox marker was detected. The fact that the change in the Electrode Response of a marker ion could be attributed to the electrostatic interaction between avidin on the Electrode surface and the redox marker ion present in a solution was verified by replacing avidin with NutrAvidin. At a pH lower than the isoelectric point of avidin, the Electrode Response of ferrocyanide as an anionic marker ion increased linearly within the range of 5.0×10−9 −3.0×10−8 M avidin. The relative standard deviation at 1.5×10−8 M avidin was about 5.4% (n=5). The detection of biotin was also performed using a competitive reaction between biotin in solution and biotin that had been immobilized on the Electrode surface in the form of the biotinylated polypyrrole.
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Voltammetric behavior of avidin-biotin interaction at a biotin/thionine modified Au Electrode
Journal of Electroanalytical Chemistry, 2002Co-Authors: Kazuharu Sugawara, Hideki Kuramitz, Ryo Kato, Tatsuya Shirotori, Shunitz TanakaAbstract:Abstract Avidin–biotin interaction at a biotin/thionine modified Au Electrode was investigated with voltammetry. The Electrode was modified with a self-assembled monolayer (SAM). The avidin–biotin interaction was monitored through change of the Electrode Response of thionine. The Electrode Response decreased with increasing concentration of the avidin. This is because the thionine moiety was held at the binding site due to the avidin–biotin interaction. Furthermore, the length of spacer between the thionine and biotin moieties, which influences the avidin–biotin binding, was examined.
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Electrochemical Detection of the Interaction Between Avidin and Biotin Based on the Change of Electrode Response of Copper Enhanced by Biotin Labeled with Thiourea
Electroanalysis, 2000Co-Authors: Hideki Kuramitz, Junpei Natsui, Shunitz Tanaka, Kiyoshi HasebeAbstract:A new avidin-biotin assay based on monitoring the change in the Electrode Response of the copper enhanced by the labeled biotin was investigated. The biotin labeled with thiourea was prepared as a bifunctional compound. The labeled biotin exhibited a high enhancement effect toward the anodic stripping wave of copper as well as a specifical binding with avidin. The anodic stripping wave of copper decreased when the labeled biotin bound with avidin. The calibration plot for avidin was linear between 1.0×10–8 mol/L and 1.0×10–7 mol/L. The relative standard deviation at 4.0×10–8 mol/L avidin was 7.7 % (n=5). The detection of biotin was performed by the competitive reaction between the labeled biotin and unlabeled biotin for the limited binding sites of avidin. The relative standard deviation at 1.0×10–7 mol/L biotin was 9.6 % (n=5) with a detection limit of 2.9×10–8 mol/L. The presence of ascorbic acid more than 2000 times toward the concentration of biotin did not interfere with the detection of 1.0×10–7 mol/L biotin.
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Electrochemical Sensing of Avidin–Biotin Interaction Using Redox Markers
Electroanalysis, 2000Co-Authors: Hideki Kuramitz, Kazuharu Sugawara, Shunitz TanakaAbstract:The interaction between avidin and biotin immobilized in self-assembled monolayer (SAM) on a gold Electrode surface was electrochemically evaluated by monitoring the changes in the Electrode Response of three hydrophilic redox markers. The introduction of avidin membrane onto the biotin-SAM Electrode surface caused the large changes in the Electrode Response of the redox marker. By using NutrAvidin instead of avidin, it was clarified that the changes of the Electrode Response were ascribed to the permeability of the marker through the avidin membrane on the Electrode surface. At a lower pH than the isoelectric point of avidin, the Electrode Response of ferrocyanide ions as an anionic redox marker ions increased linearly over the range of 1.25×10–9–1.25×10–8 M avidin. The relative standard deviation at 2.25×10–9 M avidin was about 3.9% (n=5). On the other hand, the detection of biotin was performed using a competitive reaction between biotin in the solution and biotin in SAM on the Electrode surface for avidin.
Hideki Kuramitz - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical immunoassay at a 17β-estradiol self-assembled monolayer Electrode using a redox marker
The Analyst, 2003Co-Authors: Hideki Kuramitz, Kazuharu Sugawara, Mari Matsuda, Jennifer H. Thomas, Shunitz TanakaAbstract:A simple electrochemical immunoassay was demonstrated using a 17β-estradiol modified Electrode. 17β-estradiol was immobilized on the gold Electrode surface with a self-assembly technique. The specific binding between estradiol antibody and 17β-estradiol on the Electrode surface was evaluated by monitoring the change in the Electrode Response with three hydrophilic redox markers. The decrease in the Electrode Response for the redox marker was observed, when the antibody was bound to the estradiol self-assembled monolayer (SAM) Electrode surface. The change in the Electrode Response of the redox marker is attributed to the steric hindrance between the antibody on the Electrode surface and the redox marker. The relative standard deviation at 30 μg ml−1 estradiol antibody was 4.1% (n = 3). The competitive reaction between the antigen in the solution and 17β-estradiol immobilized on the Electrode surface for the limited binding sites on the antibody produced an increase in the Electrode Response with hydroquinone as the marker. The binding affinity of three antigens including 17β-estradiol to the estradiol antibody was evaluated. Furthermore, the result obtained from this method was compared with the previously reported enzyme binding assay using the biotinylated estradiol and the biotin-immobilized microtiter plate.
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Electrochemical Evaluation of the Interaction between Avidin and Biotin at Biotinylated Polypyrrole Electrode Using a Redox Marker
Electroanalysis, 2003Co-Authors: Hideki Kuramitz, Kazuharu Sugawara, Mari Matsuda, Shunitz TanakaAbstract:The interaction between avidin and biotin was evaluated electrochemically by monitoring the change in the Electrode Response of redox markers. Biotin was immobilized on the Electrode surface by means of the electrochemical polymerization of biotinylated pyrrole and pyrrole. When avidin was introduced onto the biotinylated polypyrrole Electrode surface, the large change in the Electrode Response of the redox marker was detected. The fact that the change in the Electrode Response of a marker ion could be attributed to the electrostatic interaction between avidin on the Electrode surface and the redox marker ion present in a solution was verified by replacing avidin with NutrAvidin. At a pH lower than the isoelectric point of avidin, the Electrode Response of ferrocyanide as an anionic marker ion increased linearly within the range of 5.0×10−9 −3.0×10−8 M avidin. The relative standard deviation at 1.5×10−8 M avidin was about 5.4% (n=5). The detection of biotin was also performed using a competitive reaction between biotin in solution and biotin that had been immobilized on the Electrode surface in the form of the biotinylated polypyrrole.
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Voltammetric behavior of avidin-biotin interaction at a biotin/thionine modified Au Electrode
Journal of Electroanalytical Chemistry, 2002Co-Authors: Kazuharu Sugawara, Hideki Kuramitz, Ryo Kato, Tatsuya Shirotori, Shunitz TanakaAbstract:Abstract Avidin–biotin interaction at a biotin/thionine modified Au Electrode was investigated with voltammetry. The Electrode was modified with a self-assembled monolayer (SAM). The avidin–biotin interaction was monitored through change of the Electrode Response of thionine. The Electrode Response decreased with increasing concentration of the avidin. This is because the thionine moiety was held at the binding site due to the avidin–biotin interaction. Furthermore, the length of spacer between the thionine and biotin moieties, which influences the avidin–biotin binding, was examined.
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Electrochemical Detection of the Interaction Between Avidin and Biotin Based on the Change of Electrode Response of Copper Enhanced by Biotin Labeled with Thiourea
Electroanalysis, 2000Co-Authors: Hideki Kuramitz, Junpei Natsui, Shunitz Tanaka, Kiyoshi HasebeAbstract:A new avidin-biotin assay based on monitoring the change in the Electrode Response of the copper enhanced by the labeled biotin was investigated. The biotin labeled with thiourea was prepared as a bifunctional compound. The labeled biotin exhibited a high enhancement effect toward the anodic stripping wave of copper as well as a specifical binding with avidin. The anodic stripping wave of copper decreased when the labeled biotin bound with avidin. The calibration plot for avidin was linear between 1.0×10–8 mol/L and 1.0×10–7 mol/L. The relative standard deviation at 4.0×10–8 mol/L avidin was 7.7 % (n=5). The detection of biotin was performed by the competitive reaction between the labeled biotin and unlabeled biotin for the limited binding sites of avidin. The relative standard deviation at 1.0×10–7 mol/L biotin was 9.6 % (n=5) with a detection limit of 2.9×10–8 mol/L. The presence of ascorbic acid more than 2000 times toward the concentration of biotin did not interfere with the detection of 1.0×10–7 mol/L biotin.
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Electrochemical Sensing of Avidin–Biotin Interaction Using Redox Markers
Electroanalysis, 2000Co-Authors: Hideki Kuramitz, Kazuharu Sugawara, Shunitz TanakaAbstract:The interaction between avidin and biotin immobilized in self-assembled monolayer (SAM) on a gold Electrode surface was electrochemically evaluated by monitoring the changes in the Electrode Response of three hydrophilic redox markers. The introduction of avidin membrane onto the biotin-SAM Electrode surface caused the large changes in the Electrode Response of the redox marker. By using NutrAvidin instead of avidin, it was clarified that the changes of the Electrode Response were ascribed to the permeability of the marker through the avidin membrane on the Electrode surface. At a lower pH than the isoelectric point of avidin, the Electrode Response of ferrocyanide ions as an anionic redox marker ions increased linearly over the range of 1.25×10–9–1.25×10–8 M avidin. The relative standard deviation at 2.25×10–9 M avidin was about 3.9% (n=5). On the other hand, the detection of biotin was performed using a competitive reaction between biotin in the solution and biotin in SAM on the Electrode surface for avidin.
Kazuharu Sugawara - One of the best experts on this subject based on the ideXlab platform.
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Electrochemically monitoring the binding of concanavalin A and ovalbumin
Talanta, 2011Co-Authors: Kazuharu Sugawara, Asako Yugami, Toshihiko Kadoya, Kohei HosakaAbstract:Abstract To evaluate protein–protein interactions, a new voltammetric method was developed using a protein labeled with an electroactive compound. Concanavalin A (ConA), which is a lectin, recognizes α-mannose residues. Because the ConA was to be bound to ovalbumin (OVA), which has a high-mannose sugar chain, ConA labeled with daunomycin was prepared as the probe to monitor the binding. The binding to OVA was caused by the label modification of the ConA. As a result, the Electrode Response of the labeled ConA decreased as the OVA concentration increased. The Electrode Response of the labeled ConA was linearly over the range of 1.5 × 10−10 and 1.5 × 10−9 M OVA. The relative standard deviation of 1.5 × 10−8 M labeled ConA and 1.5 × 10−10 M OVA was 6.9% (n = 5). The labeled ConA–OVA binding could then be conveniently monitored based on the change in Response. In contrast, interactions between the labeled ConA and a protein with no specific sugar chain also were investigated. Incubation scarcely influenced the peak current of the labeled ConA. When several concentrations of OVA were added to a serum, good recovery determined it. Consequently, this method could be applied to the measurement of protein–protein interactions.
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Electrochemical immunoassay at a 17β-estradiol self-assembled monolayer Electrode using a redox marker
The Analyst, 2003Co-Authors: Hideki Kuramitz, Kazuharu Sugawara, Mari Matsuda, Jennifer H. Thomas, Shunitz TanakaAbstract:A simple electrochemical immunoassay was demonstrated using a 17β-estradiol modified Electrode. 17β-estradiol was immobilized on the gold Electrode surface with a self-assembly technique. The specific binding between estradiol antibody and 17β-estradiol on the Electrode surface was evaluated by monitoring the change in the Electrode Response with three hydrophilic redox markers. The decrease in the Electrode Response for the redox marker was observed, when the antibody was bound to the estradiol self-assembled monolayer (SAM) Electrode surface. The change in the Electrode Response of the redox marker is attributed to the steric hindrance between the antibody on the Electrode surface and the redox marker. The relative standard deviation at 30 μg ml−1 estradiol antibody was 4.1% (n = 3). The competitive reaction between the antigen in the solution and 17β-estradiol immobilized on the Electrode surface for the limited binding sites on the antibody produced an increase in the Electrode Response with hydroquinone as the marker. The binding affinity of three antigens including 17β-estradiol to the estradiol antibody was evaluated. Furthermore, the result obtained from this method was compared with the previously reported enzyme binding assay using the biotinylated estradiol and the biotin-immobilized microtiter plate.
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Electrochemical Evaluation of the Interaction between Avidin and Biotin at Biotinylated Polypyrrole Electrode Using a Redox Marker
Electroanalysis, 2003Co-Authors: Hideki Kuramitz, Kazuharu Sugawara, Mari Matsuda, Shunitz TanakaAbstract:The interaction between avidin and biotin was evaluated electrochemically by monitoring the change in the Electrode Response of redox markers. Biotin was immobilized on the Electrode surface by means of the electrochemical polymerization of biotinylated pyrrole and pyrrole. When avidin was introduced onto the biotinylated polypyrrole Electrode surface, the large change in the Electrode Response of the redox marker was detected. The fact that the change in the Electrode Response of a marker ion could be attributed to the electrostatic interaction between avidin on the Electrode surface and the redox marker ion present in a solution was verified by replacing avidin with NutrAvidin. At a pH lower than the isoelectric point of avidin, the Electrode Response of ferrocyanide as an anionic marker ion increased linearly within the range of 5.0×10−9 −3.0×10−8 M avidin. The relative standard deviation at 1.5×10−8 M avidin was about 5.4% (n=5). The detection of biotin was also performed using a competitive reaction between biotin in solution and biotin that had been immobilized on the Electrode surface in the form of the biotinylated polypyrrole.
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Voltammetric behavior of avidin-biotin interaction at a biotin/thionine modified Au Electrode
Journal of Electroanalytical Chemistry, 2002Co-Authors: Kazuharu Sugawara, Hideki Kuramitz, Ryo Kato, Tatsuya Shirotori, Shunitz TanakaAbstract:Abstract Avidin–biotin interaction at a biotin/thionine modified Au Electrode was investigated with voltammetry. The Electrode was modified with a self-assembled monolayer (SAM). The avidin–biotin interaction was monitored through change of the Electrode Response of thionine. The Electrode Response decreased with increasing concentration of the avidin. This is because the thionine moiety was held at the binding site due to the avidin–biotin interaction. Furthermore, the length of spacer between the thionine and biotin moieties, which influences the avidin–biotin binding, was examined.
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Electrochemical Sensing of Avidin–Biotin Interaction Using Redox Markers
Electroanalysis, 2000Co-Authors: Hideki Kuramitz, Kazuharu Sugawara, Shunitz TanakaAbstract:The interaction between avidin and biotin immobilized in self-assembled monolayer (SAM) on a gold Electrode surface was electrochemically evaluated by monitoring the changes in the Electrode Response of three hydrophilic redox markers. The introduction of avidin membrane onto the biotin-SAM Electrode surface caused the large changes in the Electrode Response of the redox marker. By using NutrAvidin instead of avidin, it was clarified that the changes of the Electrode Response were ascribed to the permeability of the marker through the avidin membrane on the Electrode surface. At a lower pH than the isoelectric point of avidin, the Electrode Response of ferrocyanide ions as an anionic redox marker ions increased linearly over the range of 1.25×10–9–1.25×10–8 M avidin. The relative standard deviation at 2.25×10–9 M avidin was about 3.9% (n=5). On the other hand, the detection of biotin was performed using a competitive reaction between biotin in the solution and biotin in SAM on the Electrode surface for avidin.
Konstantin N. Mikhelson - One of the best experts on this subject based on the ideXlab platform.
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Ion-selective Electrodes under galvanostatic polarization conditions
Russian Journal of Electrochemistry, 2010Co-Authors: M. A. Peshkova, Konstantin N. MikhelsonAbstract:The application of ion-selective Electrodes (ISE) with ionophore-based membranes under galvanostatic polarization conditions is briefly reviewed. The possibilities offered by polarization for expanding the working range of ISE and for varying their selectivity and the type of Electrode Response (cationic or anionic) are discussed.
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Numeric Simulation of Ion-Site Association Effects in Ion-Selective Electrode Response
Electroanalysis, 2003Co-Authors: Konstantin N. MikhelsonAbstract:Effects in ion-selective Electrode Response and selectivity, caused by ion-site association in membranes are studied by means of numeric simulations based on a generalized model, which does not rely on a certain degree of the dissociation of electrolytes in membranes. The variability of the experimental values of the potentiometric selectivity coefficients is considered in view of the association in membranes. The reasons why the “dissociation approach” often fits experimental data are also discussed. A novel version of segmented sandwich membrane method is proposed for direct potentiometric measurements of ion-site association constants in membranes, and preliminary experimental results are presented.
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Contribution of the Diffusion Potential to the Membrane Potential and to the Ion-Selective Electrode Response
Electroanalysis, 1999Co-Authors: Konstantin N. Mikhelson, Andrzej Lewenstam, Svetlana E. DidinaAbstract:A generalized quasi-thermodynamic theory of the solvent polymeric ion-selective membranes containing ion-exchanging sites (charged carrier) and a co-exchanger (ionic additives) and in contact with two mixed aqueous solutions of electrolytes IX2 and JX is developed. To account for diffusion potential it is proposed to assume various profiles of species in the diffusion layer. A computer simulation of the potentiometric signal and of its selectivity is fulfilled. A surprising result of the simulations is that though the value of diffusion potential achieves sometimes several tens of mV, it is almost the same for different profiles assumed. If being profile-independent, the diffusion potential occurs also time-independent. Therefore the usually fast Response of ISEs actually does not mean that only boundary potentials matter. The variability of selectivity coefficients to a large extent is also caused by diffusion potential. Artificial elimination of the diffusion potential with ionic additives to membranes based on calcium dioctylphenylphosphate allows one to eliminate the peculiarities like Ca/pH potential dips and also to stabilize selectivity coefficients.
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Contribution of the Diffusion Potential to the Membrane Potential and to the Ion‐Selective Electrode Response
Electroanalysis, 1999Co-Authors: Konstantin N. Mikhelson, Andrzej Lewenstam, Svetlana E. DidinaAbstract:A generalized quasi-thermodynamic theory of the solvent polymeric ion-selective membranes containing ion-exchanging sites (charged carrier) and a co-exchanger (ionic additives) and in contact with two mixed aqueous solutions of electrolytes IX2 and JX is developed. To account for diffusion potential it is proposed to assume various profiles of species in the diffusion layer. A computer simulation of the potentiometric signal and of its selectivity is fulfilled. A surprising result of the simulations is that though the value of diffusion potential achieves sometimes several tens of mV, it is almost the same for different profiles assumed. If being profile-independent, the diffusion potential occurs also time-independent. Therefore the usually fast Response of ISEs actually does not mean that only boundary potentials matter. The variability of selectivity coefficients to a large extent is also caused by diffusion potential. Artificial elimination of the diffusion potential with ionic additives to membranes based on calcium dioctylphenylphosphate allows one to eliminate the peculiarities like Ca/pH potential dips and also to stabilize selectivity coefficients.
Mark A. Adams - One of the best experts on this subject based on the ideXlab platform.
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Direct determination of phosphate in soil extracts by potentiometric flow injection using a cobalt wire Electrode
Analytica Chimica Acta, 1998Co-Authors: Zuliang Chen, Pauline F. Grierson, Mark A. AdamsAbstract:Abstract A system is described for the direct potentiometric flow injection analysis of phosphates using a cobalt wire Electrode. It is proposed that the Electrode Response to phosphate is a result of Co 3 (PO) 2 precipitate formation at the Electrode surface. The Electrode Response to phosphate was found to be depend on the phthalate concentration, carrier pH, flow rate and injected volume. A linear Response with a slope of −41±0.5 mV/decade was obtained in the concentration range of 1.0×10 −5 – 5.0×10 −3 M with a detection limit of 1×10 −6 M, using a carrier solution containing 25 mM potassium hydrogen phthalate at pH 4.0. The proposed method was used for the determination of soil extracts with a fast analysis, low cost, high sensitivity and selectivity.
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A metallic cobalt Electrode for the indirect potentiometric determination of calcium and magnesium in natural waters using flow injection analysis.
Talanta, 1998Co-Authors: Zuliang Chen, Mark A. AdamsAbstract:Abstract A flow injection analysis of Ca2+ and Mg2+ using indirect potentiometric detection in natural waters is proposed, where Ca2+ or Mg2+ are injected into a buffer carrier containing phosphate, resulting in the formation of Ca3(PO4)2 or Mg3(PO4)2. The consequent reduction in free phosphate in the carrier solution is detected using a metallic cobalt wire Electrode. Indirect Electrode Response was used and the experimental conditions affecting Electrode Response were optimized. Responses were linear in the concentration range 5×10−4 to 5×10−3 M with a detection limit of 1×10−5 M in 20 mM phosphate buffer at pH 8.0. The relative standard derivation at 1 mM of Ca2+ and Mg2+ were 3.9 and 3.7% (n=10), respectively. EGTA and 8-hydroxyquinoline were used as the masking agents for Ca2+ and Mg2+, respectively. Concentrations of Ca2+ and Mg2+ in natural waters were successfully determined by the proposed method.