JPS6371649A - Gas sensor - Google Patents

Abstract

PURPOSE:To miniaturize a biosensor and to simultaneously measure many components by combining >=2 working electrodes with one pair of a counter electrode and an electrolyte. CONSTITUTION:Different working electrodes 1a-1c are combined with the pair of the counter electrode 2 and electrolyte 3 independently of the another. An oxygen sensor shown as an example is constituted by fixing cathodes 5a-5c of gold covered with an FEP film on cathodes of a U-shape oxygen permeable film retainers 11a-11c. Cathodes 15a-15c are cathode lead-out parts which are connected to the cathodes 5a-5c and connect wiring to the respective cathodes. Thus, plural working electrodes are present in one gas sensor, so a multifunctional biosensor is easily manufacture. Further, the counter electrode and electrolyte are used in common, so that the sensor is miniaturized.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a gas sensor used as a transducer in a biosensor, by configuring a plurality of working electrodes on one gas sensor. This made measurement possible.

[Industrial application field]

Biosensors, which have been actively researched recently, have a structure that combines a molecular recognition part (receptor) in which a biologically relevant substance as a molecular recognition element is immobilized on a J3 membrane, and a signal conversion part (transducer). There is. The transducer is
physical or chemical changes that occur in receptors;
Specifically, it has the ability to convert changes that occur as a result of the reaction between the substance to be measured and the biological substance on the receptor to form a complex into electrical output. The present invention relates to the improvement of gas sensors, typified by oxygen sensors, which are increasingly being used as biosensors as transducers.

[Conventional technology]

A conventional gas sensor includes a working electrode 1, a counter electrode 2, an electrolytic solution 3, and a gas permeable membrane 4, as schematically shown in FIG. The gas to be measured passes through the gas permeable membrane 4 and is oxidized or reduced on the working electrode l. At this time, by measuring the current flowing between the working electrode 1 and the counter electrode 2, it is possible to know the gas temperature of 4 degrees.

As an example of a gas sensor, an oxygen sensor used for a glucose electrode as an example of an enzyme sensor using amberometry is as follows (ed. by Shu Suzuki).
(See "Ion Electrodes and Enzyme Electrodes," Kodansha) The two examples of glucose electrodes are composed of a glucose oxidase-immobilized membrane and an oxygen sensor. The oxygen sensor used here is of a type known as a dissolved oxygen meter, and uses a lead electrode as the counter electrode (here, the anode) and a platinum electrode as the working electrode (here, the cathode). A highly concentrated alkaline solution such as 30% NaOH or KOH is used as the electrolyte, and the platinum electrode is a thin film permeable to oxygen gas.
For example, it is coated with a Teflon (trade name) film. This oxygen sensor was created with the focus on the fact that the dissolved oxygen concentration is proportional to the oxygen partial pressure. When this sensor is inserted into a solution, the dissolved oxygen in the solution passes through the gas permeable membrane and is deposited onto the platinum electrode. electric current is obtained because it is reached and reduced here.

This current value is proportional to 23 degrees of dissolved oxygen. A glucose electrode is manufactured by closely adhering a glucose oxidase-immobilized membrane (for example, immobilized in a collagen membrane by an entrapment method) onto the gas-permeable membrane of the oxygen sensor and fixing it with an O-ring. When this glucose electrode is inserted into a buffer solution,
A steady current can be obtained.

In this case, since glucose is not present in the sample liquid, a current value corresponding to the dissolved oxygen level in the sample is obtained. Next, when a predetermined amount of glucose is added to this sample solution, the glucose diffuses into the enzyme membrane, where it is oxidized by the action of glucose oxidase to produce gluconolactone.

This reaction consumes oxygen and produces hydrogen peroxide, reducing the oxygen concentration near the glucose oxidase membrane. Therefore, part of the oxygen that diffuses from the solution to the oxygen sensor is consumed by the enzyme reaction, resulting in a decrease in the amount of oxygen that reaches the sensor. As is clear, as the oxygen concentration reaching the oxygen sensor decreases, the current value gradually decreases. However, since the glucose and oxygen that diffuse into the glucose oxidase membrane from the solution become stationary, an equilibrium is established between the amount of oxygen consumed by the membrane and the amount of oxygen that diffuses from the solution, and a steady current value is obtained. This steady-state current value depends on the glucose concentration in the sample solution.

Therefore, by measuring the current value for each glucose of known concentration and creating a calibration curve, the oxygen sensor can measure the unknown concentration of glucose in the sample liquid using this calibration curve.

[Problem that the invention seeks to solve]

The ultimate goal of a biosensor is to miniaturize it and make it possible to measure multiple components simultaneously, that is, to make it multifunctional. However, in reality, the gas sensor used as the transducer has only one working electrode in one sensor, so it has the disadvantage that it can only measure a single substance. In order to make measurements, multiple gas sensors had to be used, and miniaturization could not be achieved. The present invention seeks to solve these problems.

[Means for solving problems]

According to the present invention, the above-mentioned problems are solved by an electrochemical gas sensor that measures gas 4 degrees using an electrode reaction.
A solution can be provided by a gas sensor characterized in that it combines a pair of counter electrodes and two or more working electrodes for an electrolyte.

The principle of the gas sensor according to the present invention is illustrated in FIG. 1. That is, the gas sensor of the present invention is characterized in that different working electrodes 1a, lb, and ICs are independently combined with each other for a pair of counter electrode 2 and electrolyte 3. The gas permeable membranes 4a, 4b and 4C are made of the same or different gas permeable thin films, for example Teflon (
(trade name) and fluororesin films such as FEP (fluorinated ethylene propylene), silicone rubber, etc. Each gas permeable membrane can have a molecular recognition part (receptor) above it, which can be applied in a conventional manner. In addition, in the case of the illustrated example,
Although three working electrodes are used, two working electrodes or four or more working electrodes may be used depending on the number of gas components being measured.

The present invention can be widely applied to electrochemical gas sensors, and specifically includes a typical oxygen (02) sensor, a CO sensor, a 30W sensor, a NO□ sensor, a No sensor, and the like.

In this specification, the terms working electrode and counter electrode are used as described above, since the cathode and anode may be changed depending on the type of gas to be measured.

[For production]

Since the plurality of working electrodes of the gas sensor of the present invention each have an independent gas permeable membrane, each working electrode can be operated independently of its neighbor.

A receptor suitable for the gas to be measured can be combined with each gas permeable membrane.

〔Example〕

Next, the present invention will be explained using an oxygen sensor as an example of the present invention with reference to FIGS. 2 and 3 (A> and (B)).

In the oxygen sensor exemplified here, the working electrode is a gold or platinum cathode, the counter electrode is a silver anode, the electrolyte is a 1 mol potassium chloride aqueous solution, and the gas permeable membrane is an FEP film. In the figure, 5a, 5b and 5C are FE
The gold cathode is covered with a P film, and the FEP film is a U-shaped oxygen permeable membrane holder.
llb and 11c are fixed on the cathode. 15
a, 15b and 15c are cathodes 5a and 5, respectively.
This is a cathode extraction part for connecting wiring to each cathode connected to b and 5C. Further, 16 is an anode take-out portion for connecting wiring to an anode (not shown). The main body 7, the bottom plate 9, and the wiring insulating film 10 are each made of photosensitive resin “A” manufactured by Asahi Kasei Corporation.
PR” (product name) and is small (approximately 10
Uax approx. 25mm), L is also precise. Note that each of the FEP films coated with the gold cathode is provided with a receptor, such as an oxygen fixing membrane, a microorganism fixing membrane, etc., although not shown.

The assembly of the oxygen sensor shown in FIG. 2 will be readily understood from FIGS. 3A and 3B, which are exploded views of the sensor. A bottom plate 8 coated with a silver anode 6 as a thin film is prepared, as shown in Figure (B). On this bottom plate 8, there is a figure (
The main body 7 shown in A), which has an electrolyte reservoir 9 configured to store potassium chloride electrode solution, is inverted and glued, a cathode is attached, an electrolyte is injected, and an oxygen permeable membrane is attached. . In this way, the oxygen sensor shown in FIG. 2 is completed.

〔Effect of the invention〕

According to the present invention, since a plurality of working electrodes are present in one gas sensor, a multifunctional biosensor can be easily produced. Furthermore, since the counter electrode and electrolyte are common, it is possible to reduce the size of the sensor.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the principle of the gas sensor of the present invention, Figure 2 is a diagram explaining the principle of the gas sensor of the present invention.
The figure is a perspective view showing one embodiment of the present invention, FIG. 3 is an exploded view of the embodiment of FIG. 2, and FIG. 4 is a principle diagram of a conventional gas sensor. In the figure, la, lb and IC are working electrodes, 2 is a counter electrode, 3 is an electrolyte, and 4a, 4b and 4C are gas permeable membranes.

Claims (1)

[Claims] 1. An electrochemical gas sensor that measures gas concentration using an electrode reaction, which includes a pair of counter electrodes (2) and an electrolyte (3).
) with two or more working electrodes (1a, 1
A gas sensor characterized by a combination of (b,...).