Ion concentration measurement method

• US 5,139,626 A
• Filed: 10/31/1990
• Issued: 08/18/1992
• Est. Priority Date: 10/02/1985
• Status: Expired due to Fees

• Current Assignee: Terumo Corporation
• Original Assignee: Terumo Corporation
• Inventors: Yamaguchi, Shuichiro, Shimomura, Takeshi, Ushizawa, Norihiko
• Primary Examiner(s): Tung, T.
• Application Number:
  US07/607,856
• Time in Patent Office: 657 Days
• Field of Search: 204/153.1, 204/416-419, 204/435, 204/153.13, 204/153.15, 204/153.16, 204/153.21
• US Class Current: 205/778.5
• CPC Class Codes: G01N 27/4035 Combination of a single ion-sensing electrode and a single reference electrode G01N27/406 and G01N27/413 take precedence
• CPC Class Codes: G01N 27/48 using polarography, i.e. measuring changes in current under a slowly-varying voltage

Abstract

An electrochemical cell is formed by immersing an electrochemical ion sensor and a reference electrode into a solution of interest, the electrochemical ion sensor exhibiting ion selectivity with respect to an ion of interest and having a high electrode resistance. A current which flows through the electrochemical cell is measured while the potential of the electrochemical ion sensor is held to a constant potential with respect to the reference electrode. The current so obtained are proportional to the logarithm value of the concentration of the ion.

Claims

1. A method of measuring ionic concentration comprising the steps of:

forming an electrochemical cell by immersing an electrochemical ion sensor having a resistivity of more than 10³ Ω

/cm² and a reference electrode into a solution of interest;

measuring a current which flows through said electrochemical cell while the electrochemical ion sensor is held at a constant potential with respect to the reference electrode; and

determining ionic concentration value from the measured current on the basis of proportional relation between the measured current and the logarithm of the ionic concentration;

said electrochemical ion sensor comprising an electrically conductive substrate, an electrolytically polymerized redox polymer layer fixing a material capable of undergoing a quinone-hydroquinone type redox reaction coating a surface of said electrically conductive substrate, and an ion selective layer exhibiting ion selectivity which is carried on a polymeric compound coating a surface of said redox polymer layer.

2. A method of measuring ionic concentration comprising the steps of:

forming an electrochemical cell by immersing an electrochemical ion sensor having a resistivity of more than 10³ Ω

/cm² and a reference electrode into a solution of interest;

measuring a current which flows through said electrochemical cell while the electrochemical ion sensor is held at a constant potential with respect to the reference electrode; and

determining ionic concentration value from the measured current on the basis of the proportional relation between the measured current and the logarithm of the ionic concentration;

said electrochemical ion sensor comprising an electrically conductive substrate, an electrolytically polymerized redox polymer layer fixing a material capable of undergoing an amine-quinoid type redox reaction coating a surface of said electrically conductive substrate, and an ion selective layer exhibiting ion selectivity which is carried on a polymeric compound coating a surface of said redox polymer layer.

3. A method of measuring ionic concentration comprising the steps of:

forming an electrochemical cell by immersing an electrochemical ion sensor having a resistivity of more than 10³ Ω

/cm² and a reference electrode into a solution of interest;

measuring a current which flows through said electrochemical cell while the electrochemical ion sensor is held at a constant potential with respect to the reference electrode; and

determining ionic concentration value from the measured current on the basis of proportional relation between the measured current and the logarithm of the ionic concentration;

said electrochemical ion sensor comprising an electrically conductive substrate, an electrolytically polymerized redox polymer layer fixing a member selected from the group consisting of poly(pyrrole) and poly(thionylene) coating a surface of said electrically conductive substrate, and an ion selective layer exhibiting ion selectivity which is carried on a polymeric compound coating a surface of said redox polymer layer.