JP4219251B2 - Component concentration measuring electrode and concentration measuring device - Google Patents

Description

  The present invention relates to a measuring apparatus for measuring the concentration of a specific component in a collected sample. In particular, the present invention relates to a measuring apparatus in which a reaction membrane such as an enzyme-immobilized membrane is attached to an electrode and the concentration is measured based on a value detected by the electrode.

As a glucose concentration measurement device, glucose oxidase (GOD), a glucose degrading enzyme, is used to decompose glucose in a sample, and the amount of hydrogen peroxide produced at that time is measured by the amount of current detected by the hydrogen peroxide electrode. A glucose concentration measurement apparatus using a measurement method for obtaining a glucose concentration in a sample from the measurement result of the current amount is known.
As such a glucose concentration measuring device, there is a device in which a reaction membrane in which GOD is immobilized is attached to a sensor electrode, and the glucose concentration in the reaction tank is measured by this sensor electrode. When the reaction film is attached to the sensor electrode, a buffer solution is spotted between the reaction film and the electrode in order to improve adhesion and prevent air bubbles from being mixed during the attachment. Alternatively, the liquid supply temperature of the buffer solution or the like to the sensor electrode is adjusted according to the electrode environment temperature to saturate the amount of dissolved air in the liquid, thereby preventing the generation of bubbles.
In addition, various attempts have been made to stabilize the measurement accuracy and improve the durability of the glucose oxidase-immobilized membrane in the glucose concentration measurement apparatus.
For example, it is a technique shown in Patent Document 1. This is for the purpose of graft-polymerizing a certain kind of hydrophilic monomer on the surface of the encapsulating film of the GOD-immobilized film, and improving the detergency of the GOD-immobilized film and encapsulating film that are reaction films.

JP-A-6-174680

The inventors have repeated a number of experiments to stabilize the measurement accuracy and improve the durability of the reaction membrane in the glucose concentration measurement device, and measure the amount of air dissolved in the buffer solution due to the temperature difference in the working environment. It has been found that it is greatly related to stabilization of the reaction and durability of the reaction membrane.
When the environmental temperature at which the reaction membrane is mounted is lower than the environmental temperature (reaction tank temperature) where the electrodes are installed, bubbles are likely to be generated in the reaction tank due to the difference in the amount of dissolved air in the liquid.
And when the amount of dissolved air in the buffer solution sent to the reaction membrane exceeds the amount of saturated air at the electrode installation environment temperature, bubbles tend to be generated.
Furthermore, when the temperature of the buffer solution sent to the reaction membrane is increased, the concentration of the buffer solution increases due to the evaporation of moisture, which may affect the measurement.
In addition, the reaction membrane is configured by laminating a plurality of membranes. When bubbles are generated in the reaction membrane, the membranes may be separated by bubbles and the reaction membrane may be destroyed.

The problems to be solved by the present invention are as described above, and the inventors have repeated a number of experiments in the concentration measuring apparatus, and by using a buffer solution that has been degassed to a saturated air amount of 30 ° C. or less, It has been found that good stability can be secured.
Next, means for solving the problem will be described.

  An electrode for introducing a buffer solution into a reaction vessel and measuring a concentration of a target component in a sample in the buffer solution as described in claim 1, wherein the degassed buffer solution is connected to an electrode reaction unit. Attach the reaction membrane to the electrode reaction part.

  As described in claim 2, the buffer solution to be spotted is a buffer solution degassed to a saturation air amount of 30 ° C. or less.

As described in claim 3, in a concentration measuring apparatus for introducing a buffer solution into a reaction tank and measuring the concentration of a target component in a sample in the buffer solution using the component concentration measuring electrode according to claim 1, The buffer solution deaerated below the saturated air amount is stored in a container that prevents contact with air, and the buffer solution in the container is introduced into the reaction vessel.

An electrode for introducing a buffer solution into a reaction vessel and measuring a concentration of a target component in a sample in the buffer solution as described in claim 1, wherein the degassed buffer solution is connected to an electrode reaction unit. And attach the reaction membrane to the electrode reaction part.
The reaction in the electrode reaction part is stabilized, and the measurement accuracy can be stabilized. Furthermore, it is difficult for bubbles to come into contact with the film body, durability of the film body can be improved, and maintainability of the concentration measuring apparatus can be improved.

As described in claim 2, since the buffer solution to be spotted is a buffer solution degassed to a saturated air amount of 30 ° C. or less,
In concentration measurement using an enzyme such as measurement of glucose concentration, stable measurement can be performed, and adverse effects due to generation of bubbles can be suppressed.

As described in claim 3, in a concentration measuring apparatus for introducing a buffer solution into a reaction tank and measuring the concentration of a target component in a sample in the buffer solution using the component concentration measuring electrode according to claim 1, Since the buffer solution deaerated below the saturated air amount is stored in a container that prevents contact with air, and the buffer solution in the container is introduced into the reaction tank,
In the concentration measuring apparatus, the time required for the measuring apparatus to become stable after maintenance can be shortened. In addition, the measurement accuracy can be stabilized. Furthermore, it is difficult for bubbles to come into contact with the film body, durability of the film body can be improved, and maintainability of the concentration measuring apparatus can be improved.

Next, an embodiment of the present invention will be described.
The present invention is not limited as long as the reaction membrane is attached to the electrode and the concentration of the target is measured. A specific example of the present invention will be described using a glucose concentration measuring device.
FIG. 1 is an overall view of the blood test apparatus, and FIG. 2 is a schematic diagram showing the configuration of the blood test apparatus.
A blood test apparatus will be described as an example of an apparatus that uses the sample suction tube of the present invention. This blood test apparatus includes a main body unit 10, a sample supply unit 11, and a bottle unit 12. The main body unit 10 includes a print unit 14 that outputs an analyzed measurement value, and a panel display of the measurement value. A display panel 13 or the like is provided.

  The nozzle drive unit 19, the pump chassis unit 20, the reaction detection unit 22 configured inside the main body unit 10, the deaeration unit 21 in which the deaeration module 73 is disposed, and the like. The deaeration module 73 of the deaeration unit 21 constitutes a part of the dissolved air removal unit 123. The deaeration module 73 performs bubble removal. In the dissolved air removal unit 123, the warming unit 23 provided in the previous stage of the deaeration module 73 warms the buffer solution to remove dissolved gas. It is removed in the degassing module 73 as bubbles.

Further, a bottle unit 12 composed of a plurality of bottles is disposed on the side of the blood test apparatus, and these include a STD liquid bottle 18, a cleaning liquid bottle 15, a buffer liquid bottle 16, a drainage bottle 17, and the like. Consists of.
A vacuum blood collection tube 40 which is a sealed container is continuously set in the sample supply unit 11. The vacuum blood collection tube 40 contains blood as a sample, and this blood is collected as a sample by a sample suction tube. Then, sampling is performed by the nozzle drive unit 19 from the vacuum blood collection tube 40 containing blood continuously supplied from the sample supply unit 11 through the plug body 41 of the vacuum blood collection tube 40.

Inside the main body of the blood test apparatus, a pump chassis 20 for supplying the liquid of the bottle unit 12 to each part is configured. A cleaning tank 25 and a reaction tank 24 are arranged inside the reaction detection unit 22. An open / close electromagnetic valve 9 is disposed in the flow path from the washing tank 25 to the reaction tank 24.
In the bottle unit 12, an STD liquid bottle 18, a cleaning liquid bottle 15, a buffer liquid bottle 16 and a drainage bottle 17 are arranged.

In the blood test apparatus, the sampling nozzle 1 of the nozzle driving unit 19 is inserted through the vacuum blood collection tube which is continuously arranged and supplied in the sample supply unit 11. Blood is aspirated by the sampling nozzle 1, and excess blood adhering to the outside of the sampling nozzle 1 is washed in the washing tank 25.
Then, a sample collected in a specific amount is supplied to the reaction tank 24, and the mixed sample is discharged by opening the open / close solenoid valves 9, 26, and 132.

The reaction vessel 24 is supplied with a buffer solution whose amount is precisely measured from the buffer solution bottle 16 by opening / closing the open / close solenoid valve 26 via the dissolved air removal unit 123. In addition, an incubator coil 74 is provided in the previous stage of the reaction tank 24 to adjust the buffer solution introduced into the reaction tank 24 to a temperature at which the measurement is performed. For example, when glucose oxidase is used, it is set to 37 ° C.
In the reaction tank 24, the sample component is measured. The measurement result is output from the print unit 14 or displayed on the display unit 13.
In the pump chassis portion 20, four reciprocating piston pumps are arranged, the buffer pump 27 is a pump for sucking and supplying the buffer solution in the buffer solution bottle 16, and the cleaning solution pump 28 is a cleaning solution. This is a pump for supplying the cleaning liquid in the bottle 15 to the suction nozzle 3. The STD liquid pump 29 is a pump that supplies the STD liquid in the STD liquid bottle 18 to the portion of the cleaning tank 25. The waste liquid pump 30 is a pump that discharges the drained liquid after the analysis into the drained bottle 17.

Next, a configuration of a glucose sensor will be described as an example of the electrode.
FIG. 3 is a diagram showing a configuration in which a glucose sensor is attached to a reaction tank, and FIG. 4 is a diagram showing a measurement principle of the glucose sensor.
The glucose sensor 41 includes an electrode 42 and a glucose oxidase-immobilized enzyme membrane (hereinafter referred to as GOD membrane) 43, and measures glucose in the reaction tank 44. The glucose sensor 41 is inserted into the reaction tank 44 with the GOD film 43 that is a reaction film body attached to the electrode 42.
A buffer solution is introduced into the reaction tank 44, and the concentration of a target substance in the sample is measured in the buffer solution by a glucose sensor 41 having a GOD film 43 as a film body attached to the exposed portion at the tip of the electrode 42. It is.
The electrode 42 is a hydrogen peroxide electrode as shown in FIG. In the GOD film 43, the electrode 42 measures the peroxide water generated in the process of degrading glucose into gluconic acid.
Thereby, the glucose concentration in the reaction tank 44 is measured.
When an external voltage is applied to the hydrogen peroxide that has reached the electrode 42, an oxidation-reduction reaction occurs, and a current flows between the anode and the cathode of the electrode 42. By measuring this current, the glucose concentration is obtained.

The GOD film 43 is wrapped with a polycarbonate film and a cellulose acetate film, and the cellulose acetate film is disposed on the electrode side. The polycarbonate membrane has 300Å holes that do not allow anything larger than glucose to pass through.
Glucose that has passed through the polycarbonate membrane is decomposed into gluconic acid and hydrogen peroxide by the action of GOD.
The generated hydrogen peroxide reaches the electrode through the cellulose acetate membrane. The cellulose acetate membrane has 5 to 6 pores, allows hydrogen peroxide to pass through, and reaches the electrode without being affected by the interference reaction by the reducing substance.
When an external voltage is applied to the hydrogen peroxide that has reached the electrode, an oxidation-reduction reaction occurs and a current flows between the anode and the cathode. Then, the amount of electrons formed by the decomposition of hydrogen peroxide at the anode is measured, and the glucose concentration is obtained using the end point method.

Next, the configuration of the electrode 42 will be described.
FIG. 5 is a partial side sectional view of the electrode.
The electrode 42 is attached to the reaction tank 44 while being held by the holder 52. The electrode 42 is inserted into the holder 52 in a state where the electrode 42 is inserted into and fixed to the cylindrical body 56. Then, plugs 54 and 54 are connected to the rear end of the electrode 42 by conducting wires.
A spring 53 is disposed between the rear end of the electrode 42 and the rear inner side of the holder 52, and the electrode 42 is configured to be slidable within the holder 52 by a certain amount. When the holder of the GOD film 43 comes into contact with the tip of the electrode 42, it slides backward on the electrode 42 and is biased toward the GOD film 43 by the spring 53. Accordingly, the tip of the electrode 42 is held in contact with the holder of the GOD film 43, and the distance between the electrode 42 and the GOD film 43 is kept constant.

A positioning pin 51 is erected at the tip of the cylindrical body 56 that holds the electrode 42. The electrode 42 and the cylinder 56 are configured so as not to rotate relative to each other, and the electrode 42 is positioned by positioning the cylinder 56.
An insertion portion for the positioning pin 51 is configured in the holder 52 mounting portion of the reaction tank 44, and the positioning pin 51 is inserted into this insertion portion to position the electrode 42 with respect to the reaction tank 42.
Note that a cap 55 is attached to the electrode 42 to be transported and stored.

Next, the configuration of the electrode tip will be described.
FIG. 6 is a diagram showing the configuration of the electrode tip, FIG. 6 (a) is a side view of the electrode, FIG. 6 (b) is a partial cross-sectional side view of the electrode tip, and FIG. 6 (c) is the front of the electrode tip. FIG.
As shown in FIG. 6A, the electrode 42 is configured such that the diameters of the rear part and the central part are larger than the diameter of the tip part A. In the center of the tip A, an anode 61 having a circular shape when viewed from the front is disposed. The side periphery of the anode 61 is covered with an insulating layer 62, and the outside of the insulating layer 62 is covered with a cathode 63. The anode 61 and the cathode 63 are insulated at the electrode 42 by the insulating layer 62.
The outside of the cathode 63 is covered with a hard resin layer 64. The electrode 42 is entirely covered with the hard resin layer 64, and the anode 61 and the cathode 63 are exposed at the tip A.
The tip of the electrode 42 is a portion where the anode 61 and the cathode 63 are exposed. Measurement is performed by the anode 61 and the cathode 63 on the exposed surface of the electrode 42.

As shown in FIG. 6 (c), grooves 65, 65,...
The groove 65 is provided from the hard resin layer 64 to the cathode 63 and the insulating layer 62 in front of the tip end portion A. The groove 65 has an elliptical shape when viewed from the front, and is provided from the hard resin layer 64 toward the anode 61.
The groove 65 is wide on the outside of the electrode 42 and has a large depth.
When viewed from the outside toward the anode 61, the shape of the groove 65 is such that the bottom surface is formed in an arc shape, shallow at the groove side and deep at the center of the groove. Furthermore, in the cross section along the extending direction of the groove 65, the bottom surface is configured linearly. The groove 65 is deep in the outer portion of the electrode 42 and shallow in the vicinity of the central portion.
The width of the groove 65 is substantially the same as or slightly smaller than the width of the anode 61.
The anode 61 and the cathode 63 are configured to protrude slightly forward from the insulating layer 62.

Next, the degassing configuration of the buffer solution will be described.
In the electrode 42, as described above, oxygen is generated by the reaction at the anode. For this reason, generation | occurrence | production of the bubble in an electrode can be suppressed by supplying the buffer solution with little dissolved amount of air to an electrode part.
By performing deaeration in advance and supplying a buffer solution with a small amount of dissolved air to the reaction tank 24, stable measurement can be performed.

Next, the degassing configuration of the buffer solution will be described with reference to FIG.
FIG. 7 is a schematic diagram illustrating a degassing configuration of the buffer solution, FIG. 7A is a schematic diagram of a degassing path, and FIG. 7B is a schematic diagram of a degassing module.
The configuration for degassing the buffer solution is mainly configured by the heating unit 23, the degassing module 72, and the air pump 73.
The buffer solution in the buffer solution bottle 16 is introduced into the heating unit 23, and the temperature of the buffer solution is set to 37 ° C. and supplied to the deaeration module 72. An air pump 73 is connected to the deaeration module 72 so that oxygen dissolved in the buffer solution passing through the deaeration module 72 is deaerated.
The buffer solution that has passed through the deaeration module 72 is introduced into the buffer solution pump 27 through the three-way valve, and is further supplied to the reaction vessel through the incubator by the buffer solution pump 27.
Since the above-described degassing configuration of the buffer solution is provided immediately before the reaction vessel for concentration measurement, a buffer solution with little dissolved air can be supplied to the reaction vessel. Thereby, stable concentration measurement can be performed.

The configuration of the deaeration module 72 will be described.
The deaeration module 72 includes a vacuum chamber 82 and a gas permeable tube 81. The gas permeable tube 81 is disposed in the vacuum chamber 82 and has a configuration in which a buffer solution passes through the gas permeable tube 81.
The above-described pump 73 is connected to the vacuum chamber 82 to reduce the pressure in the vacuum chamber 82. Thereby, the buffer solution passing through the gas permeable tube 81 is degassed under reduced pressure.
It is also possible to connect the pressure sensor 83 to the vacuum chamber 82 and control the pump 73 according to the value of the pressure sensor 83. The pressure sensor 83 recognizes the pressure in the vacuum chamber 82 and connects the pressure sensor 83 and the pump 73 to the controller 84. Then, the controller 84 can control the driving of the pump 73 to adjust the pressure in the vacuum chamber 82.

At the time of measurement, a 37 ° C. buffer solution is introduced into the reaction vessel 24, and the glucose concentration is measured at 37 ° C. By heating the buffer solution to the measurement temperature or higher, the generation of bubbles during measurement can be suppressed.
For this reason, in the pre-incubator 70, the buffer solution is heated to 37 ° C. and introduced into the deaeration module 72. And by deaerating at 37 degreeC, the dissolved amount of oxygen in measurement conditions can be reduced and efficient deaeration can be performed.
Thus, stable measurement can be performed by deaeration to a saturation air amount of 30 ° C. or less or an oxygen amount conversion of 7.5 mg / L or less.

By using the buffer solution in the buffer solution bottle 16 that has been degassed in advance, the reaction at the electrode can be stabilized and the measurement accuracy can be stabilized.
By using a buffer solution that has been degassed to a saturated air amount of 30 ° C. or less, the load on the deaeration module 72 can be reduced. In addition, the supply rate of the buffer solution can be improved, and the processing time can be shortened.
In addition, the degassed buffer solution can be sealed in a container that prevents contact with air to serve as a buffer solution supply source. For example, when a degassed buffer solution is sealed in a flexible container and the buffer is taken out from the container, the volume of the container decreases as the buffer solution decreases, and the buffer solution in the container does not come into contact with air. Thereby, it can prevent that oxygen etc. melt | dissolve in the buffer solution in a container, and can supply stably the buffer solution with little dissolved amount of oxygen.
By using such a buffer solution for concentration measurement and washing, bubbles are not easily generated in a portion where concentration measurement is performed, stable measurement can be performed, and measurement accuracy is stabilized.

Next, a method of using a degassed buffer solution when attaching the GOD film to the electrode will be described.
FIG. 8 is a diagram showing a procedure for attaching the GOD film to the electrode.
When attaching the GOD film to the electrode, first, a degassed buffer solution is dropped onto the surface of the GOD film 43 as shown in FIG. And as shown in FIG.8 (b), the front-end | tip part of the electrode 42 is faced upwards, and the deaerated buffer solution is dripped at the surface which exposed the anode and the cathode to the front-end | tip front.
And as shown in FIG.8 (c), the GOD film | membrane 43 wetted with the deaerated buffer solution is assembled | attached to the electrode 42 to which the deaerated buffer solution adhered to the front-end | tip part. Thereby, the amount of dissolved oxygen in the buffer solution between the GOD film 43 and between the GOD film 43 and the electrode 42 can be reduced, and stable measurement can be performed.

1 is an overall view of a blood test apparatus. The schematic diagram which shows the structure of a blood test apparatus. The figure which shows the mounting structure to the reaction tank of a glucose sensor. The figure which shows the measurement principle of a glucose sensor. The partial side surface sectional drawing of an electrode. The figure which shows the structure of an electrode front-end | tip part. The schematic diagram which shows the deaeration structure of a buffer solution. The figure which shows the procedure at the time of attaching a GOD film | membrane to an electrode.

Explanation of symbols

41 Glucose sensor 42 Electrode 43 GOD film 61 Anode 62 Insulating layer 63 Cathode 64 Hard resin layer 65 Groove

Claims (3)

An electrode for introducing a buffer solution into a reaction vessel and measuring the concentration of a target component in a sample in the buffer solution,
An electrode for component concentration measurement, wherein a degassed buffer solution is spotted on an electrode reaction part, and a reaction membrane is attached to the electrode reaction part.   The electrode for component concentration measurement according to claim 1, wherein the buffer solution to be spotted is a buffer solution degassed to a saturation air amount of 30 ° C or less. In a concentration measuring apparatus for introducing a buffer solution into a reaction vessel and measuring a target component concentration in a sample in the buffer solution using the component concentration measuring electrode according to claim 1,
A concentration measuring apparatus, wherein a buffer solution deaerated to a saturated air amount of 30 ° C. or less is stored in a container that prevents contact with air, and the buffer solution in the container is introduced into the reaction tank.