Microchip-based carbon dioxide gas sensor

• US 20020011408A1
• Filed: 06/08/2001
• Published: 01/31/2002
• Est. Priority Date: 06/12/2000
• Status: Active Grant

• Current Assignee: i-SENS, Inc.
• Original Assignee: i-SENS, Inc.
• Inventors: Lee, Min Hyung, Nam, Hakhyun, Cha, Geun Sig, Shin, Jae Ho, Lee, Jae Seon
• Granted Patent: US 6,746,583 B2
• Time in Patent Office: Days
• US Class Current: 204/414
• CPC Class Codes: G01N 27/27 Association of two or more measuring systems or cells, each measuring a different parameter, where the measurement results may be either used independently, the systems or cells being physically associated, or combined to produce a value for a further parameter
• CPC Class Codes: G01N 27/333 Ion-selective electrodes or membranes glass electrodes G01N27/36
• CPC Class Codes: G01N 27/4162 investigating the composition of gases, by the influence exerted on ionic conductivity in a liquid conductometry in general G01N27/06; amperometric gas sensors G01N27/404
• CPC Class Codes: G01N 33/004 CO or CO2

Abstract

There is provided a microchip-based differential-type carbon dioxide gas sensor for detecting dissolved carbon dioxide levels. It functions with at least one working electrode composed of an unbuffered hydrogel membrane containing a certain amount of sodium bicarbonate and a pH-sensitive gas-permeable membrane; and a reference electrode composed of a buffered hydrogel membrane and a pH-sensitive gas-permeable membrane. The unbuffered hydrogel membrane contains carbonic anhydrase, which reduces the time period for the hydration of carbon dioxide, thereby allowing the quick measurement of the level of carbon dioxide. In addition to being significantly improved in stabilization, sensing, and recovering time periods, the differential-type carbon dioxide gas sensor can be fabricated in small sizes and quickly measure levels of carbon dioxide dissolved in sample solution.

Claims

1. A microchip-based differential-type carbon dioxide gas sensor, comprising:

a) a working electrode composed of unbuffered hydrogel and pH-sensitive gas-permeable membrane, wherein carbonic anhydrese is incorporated into a unbuffered hydrogel; and

,

b) a reference electrode composed of buffered hydrogel and pH-sensitive gas-permeable membrane.

2. The microchip-based differential-type carbon dioxide gas sensor, as set forth in claim 1, comprising:

a) a substrate;

b) multiple electrodes arranged at an approximate distances on the substrate, wherein the one is used as a reference electrode and the others are used as working electrodes;

c) an insulating film for separating the electrode layers deposited over the substrate, except for the areas for the electrode sites;

d) pH-sensitive gas-permeable membranes, placed atop of each of the electrodes;

e) unbuffered hydrogel membranes containing carbonic anhydrase, placed between the working electrode layer and the pH-sensitive gas-permeable membrane; and

f) a buffered hydrogel membrane, placed between the reference electrode layer and the pH-sensitive gas-permeable membrane.

3. The microchip-based differential-type carbon dioxide gas sensor as set forth in claim 2, wherein the substrate is selected from the group of alumina, ceramic, silicon, and plastic material, more preferably is used alumina one.

4. The microchip-based differential-type carbon dioxide gas sensor as set forth in claim 2, wherein the unbuffered hydrogel membrane is composed of a hydrogel comprising 2.4×

10<sup>−

2</sup>˜

8.1×

10<sup>−

2</sup>% by weight (3˜

10 mM) of sodium bicarbonate, 5.6×

10<sup>−

4</sup>˜

5.6×

10<sup>−

3</sup>% by weight (0.1˜

1.0 mM) of sodium chloride or potassium chloride and 1˜

4% by weight of a hygroscopic material, and carbonic anhydrase in an amount of 0.1˜

6.0 mg per ml of the hydrogel.

5. The microchip-based differential-type carbon dioxide gas sensor as set forth in claim 4, wherein the hygroscopic material is selected from hydroxyethyl cellulose, poly(vinyl alcohol), Methocel, (hydroxypropyl)methyl cellulose, polyacrylic acid, polyvinylpyrrolidone, poly(methylmethacrylate), agar and gelatin.

6. The microchip-based differential-type carbon dioxide gas sensor as set forth in claim 2, wherein the buffered hydrogel membrane is prepared from a solution of 1˜

5 mM sodium chloride or potassium chloride and 1˜

4% by weight of the hygroscopic material in an acidic buffer.

7. The microchip-based differential-type carbon dioxide gas sensor as set forth in claim 2, wherein the pH-sensitive gas- permeable membrane comprises 32˜

45% by weight of a polymer matrix, 1.0˜

4.5% by weight of a hydrogen ion-selective material, 50˜

66% by weight of a plasticizer, and a 0.9˜

1.5% by weight of a lipophilic additive.

8. The microchip-based differential-type carbon dioxide gas sensor as set forth in claim 7, wherein a matrix is formed of the material selected from the group consisting of PVC (poly(vinyl chloride)), PU (polyurethane), silicone rubber, and a combination thereof.

9. The microchip-based differential-type carbon dioxide gas sensor as set forth in claim 7, wherein the hydrogen ion-selective material is selected from the group consisting of TDDA (tridodecyl amine), 4-nonadecylpyridine, N,N-dioctadecylmethylamine, and octadecyl isonicotinate, TDDA (tridodecyl amine) is preferable.

10. The microchip-based differential-type carbon dioxide gas sensor as set forth in claim 7, wherein the plasticizer is DOS (bis(2-ethylhexyl)sebacate) or NPOE (2-nitrophenyl octyl ether).

11. The microchip-based differential-type carbon dioxide gas sensor as set forth in claim 7, wherein the lipophilic additive is KTpClPB (potassium tetrakis [4-chlorophenyl] borate).

12. The microchip-based differential-type carbon dioxide gas sensor as set forth in claim 7, wherein the pH-sensitive gas permeable membrane further comprises (N-[3-(trimethoxysilyl)propyl]ethylene diamine.