Method and chemical sensor for determining concentrations of hydrogen peroxide and its precursor in a liquid

• US 6,042,714 A
• Filed: 12/04/1997
• Issued: 03/28/2000
• Est. Priority Date: 05/02/1997
• Status: Expired due to Term

• Current Assignee: National Science Council
• Original Assignee: National Science Council
• Inventors: Lin, Meng Shan, Jan, Bor Iuan, Tseng, Ta Feng, Shih, Wei Chung, Wu, Yi Cong, Lai, Jung Sheng
• Primary Examiner(s): Warden, Sr., Robert J.
• Assistant Examiner(s): MCNEIL, JENNIFER C
• Application Number:
  US08/984,775
• Time in Patent Office: 845 Days
• Field of Search: 204/416, 204/403, 204/419, 205/777.5, 205/782, 205/783, 205/786, 205/794.5
• US Class Current: 205/782
• CPC Class Codes: C12Q 1/004 mediator-assisted
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: G01N 31/228 for peroxides

Abstract

A new method which employs a mixed-valence cluster of M_y^z+ [Fe(II)(CN)₆ ] coated on an electrode surface to determine hydrogen peroxide concentration electrochemically is developed. M of the mixed-valence compound can be Co, Ni, Cr, Sc, V, Cu, Mn, Ag, Eu, Cd, Zn, Ru or Rh; z is the valence state of M; and y=4/z. In addition, this invention also reveals a new approach to determine a concentration of a hydrogen peroxide precursor, wherein a catalyst is immobilized in the matrix or on the surface of the mixed-valence compound on the electrode. In a typical biochemical system, the catalyst can be a glucose oxidase and blood sugar is catalyzed to form hydrogen peroxide.

Claims

1. A chemical sensor for measuring a concentration of a H₂ O₂ precursor in a liquid, said H₂ O₂ precursor being a compound that can produce H₂ O₂ in said liquid under appropriate reaction conditions, which comprises a transducer which is able to conduct an electric current and a composition deposited on a surface of the transducer, wherein said composition comprises a catalyst for said H₂ O₂ production reaction and a mixed-valence compound having a formula as follows:

space="preserve" listing-type="equation">M.sub.y.sup.z+ [Fe(II)(CN).sub.6 ]

wherein M is Co, Ni, Cr, Sc, V, Cu, Mn, Ag, Eu, Cd, Zn, Ru, or Rh;

z is the valence of M;

y=4/z; and

the catalyst is an urea oxidase or a cholesterol oxidase.

2. The chemical sensor according to claim 1, wherein M is Co, z=2 and y=2.

3. The chemical sensor according to claim 1, wherein M is Ni, z=2 and y=2.

4. The chemical sensor according to claim 1, wherein M is Cr, z=2 and y=2.

5. The chemical sensor according to claim 1, wherein said catalyst is urea oxidase.

6. The chemical sensor according to claim 1, wherein said catalyst is cholesterol oxidase.

16. A method for measuring a H₂ O₂ precursor concentration in a solution comprising the following steps:

a) immersing a counter electrode, a reference electrode and the chemical sensor of claim 1 as a working electrode into a solution under reaction conditions;

b) obtaining a steady electric current from the working electrode by apmerometry, wherein a fixed potential between the working electrode and the reference electrode is maintained, and said fixed potential ranges from 0.0 V to -0.2 V when the reference electrode is 3 M KCl Ag/AgCl electrode; and

c) comparing the steady electric current from b) with steady electric currents obtained from solutions having known concentrations of said H₂ O₂ precursor under substantially the same operating conditions and the same fixed potential used in steps a) and b);

wherein the operating conditions comprises maintaining the solution in a homogeneous phase by stirring, and maintaining a substantially constant pH by adding a pH-buffer, and selectively adding an electrolyte to the measured solution, wherein the substantially constant pH is between 3 to 7.

17. The method according to claim 16, wherein said pH-buffer is phosphate buffer, citrate buffer, borate buffer, perchlorate buffer or acetate buffer, and an alkali metal halide is added to the solution as said electrolyte, when M is Co, z=2 and y=2 in the formula (I).

18. The method according to claim 17, wherein said alkali metal halide is KCl.

19. The method according to claim 17, wherein said pH-buffer is phosphate buffer having a pH of about 6.

20. The method according to claim 16, wherein said pH-buffer is phosphate buffer, citrate buffer, borate buffer or acetate buffer, and no electrolyte is added to the solution, when M is Ni, z=2 and y=2 in the formula (I).

21. The method according to claim 20, wherein said pH-buffer is acetate buffer having a pH of about 4.

22. The method according to claim 16, wherein said pH-buffer is succinate buffer, phosphate buffer, acetate buffer, borate buffer, imidazole buffer, citrate buffer, ammonium chloride buffer or glycine buffer, and no electrolyte is added to the solution, when M is Cr, z=2 and y=2 in the formula (I).

23. The method according to claim 22, wherein said pH-buffer is succinate buffer having a pH of about 6.

24. The method according to claim 16, wherein the solution is kept at a constant temperature of 15-30°

C.

25. The chemical sensor according to claim 16, wherein M is Cr, z=2 and y=2.

26. The chemical sensor according to claim 16, wherein said catalyst is urea oxidase.

7. A method for measuring H₂ O₂ concentration in a solution comprising the following steps:

a) immersing a counter electrode, a reference electrode and a chemical sensor as a working electrode into a solution under reaction conditions;

b) obtaining a steady electric current from the working electrode by amperometry, wherein a fixed potential between the working electrode and the reference electrode is maintained, and said fixed potential ranges from 0V to -200 mV when the reference electrode is a 3 M KCl Ag/AgCl electrode; and

c) comparing the steady electric current from b) with steady electric currents obtained from solutions having known H₂ O₂ concentrations under substantially the same operating conditions and the same fixed potential used in steps a) and b);

wherein the operating conditions comprised maintaining the solution in a homogenous phase by stirring, and maintaining a substantially constant pH by adding a pH-buffer, and selectively adding an electrolyte to the measured solution, wherein the substantially constant pH is between 3 to 7;

said chemical sensor comprising a transducer which is able to conduct an electric current and a mixed-valence compound deposited on a surface of the transducer, wherein said mixed-valence compound has a formula as follows;

space="preserve" listing-type="equation">M.sub.y.sup.z+ [Fe(II)(CN).sub.6 ]

wherein M is Co, Ni, Cr. Sc, V, Cu, Mn, Ag, Eu, Cd, Zn, Ru, or Rh;

z is the valence of M; and

y=4/z.

9. The method according to claim 7, wherein said alkali metal halide is KCl.

11. The method according to claim 7, wherein said pH-buffer is phosphate buffer, citrate buffer, borate buffer or acetate buffer, and no electrolyte is added to the solution, when M is Ni, z=2 and y=2 in the formula (I).

12. The method according to claim 11, wherein said pH-buffer is acetate buffer having a pH of about 4.

13. The method according to claim 7, wherein said pH-buffer is succinate buffer, phosphate buffer, acetate buffer, borate buffer, imidazole buffer, citrate buffer, ammonium chloride buffer or glycine buffer, and no electrolyte is added to the solution, when M is Cr, z=2 and y=2 in the formula (I).

14. The method according to claim 13, wherein said pH-buffer is succinate buffer having a pH of about 6.

15. The method according to claim 7, wherein the solution is kept at a constant temperature of 15-30°

C.

8. The method according to claim 8, wherein said pH-buffer is phosphate buffer, citrate buffer, borate buffer, perchlorate buffer or acetate buffer, and an alkali metal halide is added to the solution as said electrolyte, when M is Co, z=2 and y=2 in the formula (I).

10. The method according to claim 8, wherein said pH-buffer is phosphate buffer having a pH of about 6.