JPH07119737B2 - Solute concentration measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a concentration measuring device for obtaining a target solute concentration from an ion concentration generated by a potentiostatic electrolysis reaction of a solute to be measured.

(Prior Art) To measure the concentration of a specific solute in a solvent with an ion sensor,
Conventionally, the following devices have been used.

1) When the solute is an electrolyte A concentration measuring device characterized by detecting the ion concentration generated by the thermal ionization equilibrium reaction of the solute.

Since the ion concentration is proportional to the concentration of solute dissolved in the solvent, the principle of measurement is that the concentration of the target solute can be known by measuring the ion concentration.

2) When the solute is a non-electrolyte A substance that produces an electrolyte from a non-electrolyte, for example, a concentration measuring device that has an ion detection unit fixed to or near the ion sensitive unit such as an enzyme or a microorganism that produces an electrolyte from a non-electrolyte, For example, when an enzyme or microorganism is immobilized in or near the ion-sensing part, an electrolyte proportional to the solute of the non-electrolyte is generated, and the ion proportional to the concentration of the generated electrolyte causes a thermal ionization equilibrium reaction. And the concentration of the non-electrolyte is indirectly measured by the ion concentration measurement.

(Problems to be Solved by the Invention) The above-described concentration measuring device is based on the principle of measurement of the ion concentration generated by the thermal ionization equilibrium reaction of a part of the solute. Therefore, the lower limit of measurement of the solute concentration depends on the ionization constant that governs the ionization degree of the solute, and it becomes difficult to measure the concentration of the solute having a small ionization constant.

The first invention of the present application is made to solve the above-mentioned drawbacks in which the concentration measurement of a solute having a small ionization equilibrium constant is difficult, and the second invention is the concentration detection in the concentration measurement of a non-electrolyte. This is an improvement in sensitivity.

(Means for Solving the Problems) (1) The gist of the first invention is that the working electrode (1) and the ion sensitive field effect transistor (hereinafter abbreviated as ISFET) (2) ion sensitive part (3). And are configured in close proximity.

(2) The gist of the second invention is that the working electrode (1) or IS
A substance (11) that produces an electrolyte from a non-electrolyte, such as an enzyme or a microorganism, is immobilized on at least one surface of at least one of the ion-sensitive parts (3) of the FET (2) or in the vicinity thereof. The working electrode (1) and the ion sensitive part (3) of the ISFET (2) are arranged close to each other.

(Operation of the Invention) The first invention of the present application is the IS of the ion concentration generated in proportion to the concentration of the solute to be measured by potentiostatic electrolysis of the solute to be measured.
The concentration of the target solute is measured from the detection value by the FET.

The second invention is the constant potential electrolysis of the electrolyte generated from the solute of the non-electrolyte to be measured, the concentration of the target solute is measured from the detected value by the ISFET of the ion concentration generated in proportion to the concentration of the solute to be measured. .

(Embodiment) (Embodiment of the first invention) FIG. 1 is a circuit diagram of a solute concentration measuring apparatus showing an embodiment of the first invention. 2 and 3 are views of a solute concentration detection unit (14) in which the working electrode (1), the counter electrode (4) and the ISFET (2) are fixed by an insulator (5).
4 and 5, the working electrode (1) has an ISFET (2).
Insulating substrate (6) that is built in close to the ion sensitive part 3 and has the counter electrode (4) mounted with ISFET (2)
FIG. 4 is a view of a solute concentration detection unit (14) built and integrated on the back surface of the.

Referring to FIG. 1, a measuring circuit system according to an embodiment of the first invention will be described.

The reference electrode (12) is an electrode for accurately measuring the voltage across the interface between the working electrode (1) and the solvent (13).

The voltage required for electrolysis of the solute to be measured is applied to the working electrode (1) and the counter electrode (4). The potential difference between the working electrode (1) and the reference electrode (12) set by the set voltage (15) is constantly controlled by the amplifier (16) to a constant voltage at which the solute to be measured is selectively electrolyzed. .

The voltage between the drain (8) and the source (9) of the ISFET (2) set by the set voltage (17) is constantly controlled by the amplifier (18).

The solute to be measured touching the working electrode (1) is electrolyzed to generate ions. Selectively responds to this ion, depending on the concentration
A voltage is generated between the interface between the ion selective membrane (7) provided in the ion sensitive part (3) of the ISFET (2) and the solvent (13). The sum of the interface voltage and the voltage of the source (9) is applied between the ion selective membrane (7) and the source (9). This voltage attracts electrons to the channel (10), changes the resistance of the channel (10), and changes the current flowing from the drain (8) to the source (9). This change in current is output as an output voltage (19) corresponding to the concentration of the solute to be measured.

The result of measuring the concentration of hydrogen peroxide according to the first invention is shown in FIG. FIG. 6 shows changes in the output voltage of the concentration measuring device with respect to changes in the concentration of hydrogen peroxide in the aqueous solution.

The measurement circuit system of the embodiment for measuring the concentration of hydrogen peroxide will be described with reference to FIG.

In Fig. 1, deionized water was used as the solvent (13), and after equilibration with the room atmosphere, a hydrogen peroxide solution was added dropwise to this to examine the change in the output voltage (19) of the concentration measuring device. It was

The solute concentration detecting section (14) used for the solute concentration detection has the structure shown in FIGS. 2 and 3. Platinum wires were used for the working electrode (1) and the counter electrode (4), and they were fixed together with ISFET with a silicone resin.

A silver / silver chloride electrode (Ag / AgCl) was used as a reference electrode (12). Due to the electrolysis of hydrogen peroxide, the set voltage (15) is set so that the working electrode (1) becomes 0.7V with respect to the reference electrode (12).
Set in.

The voltage between the drain (8) and the source (9) of the ISFET (2) for detecting ions generated by electrolysis was set to 1v by the set voltage (17).

In FIG. 6, the solid line is the measured voltage according to the present invention.
The broken line is the open state in which no voltage is applied to the working electrode (1) and the counter electrode (4), that is, the concentration measurement voltage by only the conventional ISFET (2).

When the deionized water is changed to a 12 ppb aqueous solution of hydrogen peroxide by the first drop of hydrogen peroxide, the output voltage (19) of the concentration measuring device according to the present invention changes by 10 mV. On the other hand, an open state in which no voltage is applied to the working electrode (1) and the counter electrode (4) (detection state by the conventional ISFET (2) only)
Then, when the deionized water reached a hydrogen peroxide concentration of 12000 ppb, an output voltage change of 10 mv was obtained for the first time.

From this result, it is possible to detect hydrogen peroxide by the concentration measuring device of the present invention up to 1/1000 of the lower limit of the concentration detected by the conventional ISFET alone. That is, the measurement sensitivity of 1000 times was obtained.

(Embodiment of the Second Invention) FIGS. 7, 8, 9, 10, 11 and 12 are
FIG. 7 is a diagram of a solute concentration detection unit (14) for a non-electrolyte, which is an embodiment of the second invention.

FIGS. 7, 8, 9, and 10 show substances (11), such as enzymes, which produce an electrolyte from a non-electrolyte near the surface of the working electrode (1) and the ion sensitive part (3). FIG. 3 is a view of a solute concentration detection unit (14) of a non-electrolyte coated with a film on which microorganisms and the like are immobilized.

FIG. 11 and FIG. 12 show a substance (11) that produces an electrolyte from a non-electrolyte on the surface of the ion sensitive part (3) and its vicinity, for example,
FIG. 3 is a diagram of a non-electrolyte solute concentration detection unit (14) covered with a film on which an enzyme, a microorganism, or the like is immobilized.

As a working example of the measurement of the concentration of the non-electrolyte according to the second invention, the measurement result of the concentration of glucose is shown in FIG.

FIG. 13 shows the glucose concentration in the water tank and the output voltage of the concentration measuring device when the glucose aqueous solution was dropped into the deionized water of the solvent (13).

The measurement circuit system of the embodiment for measuring the concentration of glucose will be described with reference to FIG.

The solvent (13), the reference electrode (12), and the electrolysis voltage are the same as in the hydrogen peroxide concentration measurement example of the first invention.

The solute concentration detector (14) has the structure shown in FIGS. 11 and 12. As a substance (11) for producing an electrolyte from a non-electrolyte, glucose oxidase was immobilized in the vicinity of the working electrode (1) or the ion sensitive part (3) to produce an electrolyte from non-electrolyte glucose.

When glucose in aqueous solution comes into contact with glucose oxidase, this catalytic action decomposes glucose into gluconic acid and hydrogen peroxide. The concentration of hydrogen peroxide is proportional to the concentration of glucose, and when hydrogen peroxide contacts the working electrode (1) to which a voltage of 0.7 V is applied, as in the hydrogen peroxide concentration measuring example according to the first invention. It is electrolyzed to generate hydrogen ions. This hydrogen ion concentration is proportional to the glucose concentration, and the glucose concentration is measured from the detection value of the hydrogen ion concentration by ISFET (2).

Although it was difficult to measure the glucose concentration by detecting the ion concentration produced by the catalytic action of glucose oxidase by ISFET, the second invention
As shown in the figure, the measurement became possible with high sensitivity.

(Effect of the Invention) The first invention of the present application does not depend on the ionization constant that governs the ionization degree of the solute, and can significantly lower the lower limit of the low concentration measurement limit of the solute having a small ionization constant.

The second invention is a low concentration measurement of the target solute measured by the ISFET detection value of the ion concentration generated in proportion to the concentration of the measurement target solute by the constant potential electrolysis of the electrolyte generated from the solute of the non-electrolyte measurement target. It becomes possible to lower the lower limit of the limit.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a solute concentration measuring device. FIG. 2 is a front view of a solute concentration detecting portion of an electrolyte. FIG. 3 is a sectional view taken along line 2-2 ′ of a solute concentration detecting portion of an electrolyte. Fig. 5 is a sectional view of the solute concentration detector of the electrolyte, taken along line 4-4 '. Fig. 6 is the result of hydrogen peroxide concentration measurement. Fig. 7 is a front view of the solute concentration detector of the non-electrolyte Fig. 8 7-7 'cross section of non-electrolyte solute concentration detector Fig. 9 is a front view of non-electrolyte solute concentration detector Fig. 10 is cross-sectional view of non-electrolyte solute concentration detector 9-9' Fig. 11 Front view of solute concentration detector of non-electrolyte Fig. 12 is cross-sectional view of solute concentration detector of non-electrolyte 11-11 'Fig. 13 is glucose concentration measurement result 1 working electrode, 2 ISFET, 3 ion sensitive And 4 are counter electrodes, 5 is an insulator, 6 is an insulating substrate, 7 is an ion selective film, 8 is a drain, 9 is a source, and 10 is a channel. , 11 is a substance that produces an electrolyte from a non-electrolyte, that is, an immobilized membrane of an enzyme or a microorganism, 12 is a reference electrode, 13 is a solvent, 14 is a solute concentration detection unit, 15 is a voltage for setting an electrolytic voltage, 16 is an amplifier ,
17 is a drain / source voltage setting voltage, 18 is an amplifier, 19
Is the output voltage

Front Page Continuation (72) Inventor Mitsuru Tsutohi 1-5-5 Sanno 1-5, Nakagawa-ku, Nagoya, Aichi

Claims (2)

[Claims] 1. A working electrode (1) and a counter electrode (4),
A solute concentration measuring device characterized in that a working electrode (1) and an ion sensitive part (3) of an ion sensitive field effect transistor (2) are close to each other. 2. A surface of a working electrode (1) or at least one of an ion-sensitive part (3) of an ion-sensitive field effect transistor (2) having a working electrode (1) and a counter electrode (4). Or in the vicinity thereof, a substance (11) that produces an electrolyte from a non-electrolyte, that is, a working electrode (1) to which an enzyme or a microorganism is immobilized and an ion-sensitive part (3) of an ion-sensitive field effect transistor (2). A solute concentration measuring device characterized by being close to each other.