JPS6322520Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to a hydrogen peroxide electrode for enzyme electrodes that integrates a hydrogen peroxide electrode (diaphragm-covered electrode for hydrogen peroxide detection), which is a type of enzyme electrode using an immobilized enzyme membrane, and a temperature compensation electrode. . In general, enzyme electrodes are a combination of an enzyme and an electrode, and are widely used in fields such as clinical chemistry analysis and environmental analysis because of their excellent selectivity, rapidity, and accuracy of electrode reactions. ing. A hydrogen peroxide electrode, which is a type of electrode that makes up an enzyme electrode, oxidizes hydrogen peroxide produced by the catalytic action of an enzyme using an anode made of platinum or the like, and the purpose is to quantify specific components from the oxidation current value generated at this time. used in In addition, when quantifying a specific component using this type of enzyme electrode, in order to minimize the influence of temperature drift of the reaction solution on the enzyme reaction and electrode reaction, the temperature of the reaction solution is detected and the measurement circuit Temperature compensated electrodes are used for feedback. Conventionally, as an enzyme electrode having a temperature compensation function as described above, for example, as shown in Fig. 1, a hydrogen peroxide electrode and a temperature compensation electrode were installed in separate cell chambers to measure reaction current and temperature. There are known devices configured to do this. That is, the enzyme electrode shown in FIG. 1 has a hydrogen peroxide electrode 16 and a temperature compensation electrode 18 on one side of a cell 10 having a pair of cell chambers 12 and 14, corresponding to each cell chamber 12 and 14, respectively. It was installed. Note that the cell chambers 12 and 14 provided in the cell 10 communicate with each other and are filled with a phosphate buffer solution with a pH of 7;
A silicon diaphragm 20 is coated on one side of the cell so that a portion of each cell chamber 12, 14 is in contact with the outside of the cell 10 via the silicon diaphragm 20. However, in the conventional cell structure described above, the hydrogen peroxide electrode 16 detects the reaction current in the cell chamber 12, and the temperature compensation electrode 18 detects the reaction current in the cell chamber 12.
Since the temperature of the buffer is detected, if the buffer solution is not sufficiently stirred by the silicon diaphragm 20, etc.
There is a drawback that accurate reaction temperature cannot be detected. Furthermore, as the reaction temperature is raised, the drift of the residual current of the electrode increases as shown in Figure 2, so accurate detection of the reaction temperature and compensation for its drift are necessary to improve measurement accuracy. be. Furthermore, in the conventional cell structure, two electrodes are attached to a single cell, which not only makes it troublesome to drill holes in the cell and attach the electrodes. However, there is a drawback that the handling operation is complicated. In order to overcome the problems of the conventional hydrogen peroxide electrode for enzyme electrodes mentioned above, the inventors of the present invention have conducted various studies and made prototypes, and as a result, they have developed a temperature-compensated part of the silver electrode that makes up the hydrogen peroxide electrode. By integrally embedding the electrode, it is not only possible to measure the reaction temperature extremely accurately when measuring the reaction current by utilizing the thermal conductivity of the silver electrode, but also to simplify the measurement system, I discovered that all the problems could be solved. Therefore, the purpose of the present invention is to provide a peroxidation electrode for enzymes that has a simple structure and is easy to manufacture, and that has a built-in temperature compensation electrode that can improve measurement accuracy. To provide hydrogen electrodes. In order to achieve the above object, the present invention includes a cylindrical silver electrode as a counter electrode with a hole in the center, a platinum electrode as a working electrode is inserted through the center hole of this silver electrode, and A hole is drilled in a part of the back side of the silver electrode and a temperature compensating electrode such as a thermistor is inserted therein, and these platinum electrodes and temperature compensating electrodes are insulated and fixed by pouring resin onto the silver electrode to form an electrode unit. The electrode unit is characterized in that the outer surface of the electrode unit is tightly coated with an immobilized enzyme membrane. Next, an embodiment of a hydrogen peroxide electrode for an enzyme electrode incorporating a temperature compensation electrode according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 3 shows an electrode unit of a hydrogen peroxide electrode for an enzyme electrode according to the present invention, with reference numeral 30.
32 represents a silver electrode as a counter electrode, and 32 represents a platinum electrode as an anode (working electrode). A temperature compensation electrode 34 is embedded in the silver electrode 30, and these platinum electrode 32 and temperature compensation electrode 34 are connected via an insulating layer 36. It is fixed to a silver electrode 30. Note that the silver electrode 30,
Lead wires 38, 40 and 42 are led out from the platinum electrode 32 and the temperature compensation electrode 34, respectively. When manufacturing a hydrogen peroxide electrode having such a configuration, first, a silver rod is machined to form a cylindrical silver electrode 30 shown in FIG. 3. Next, a hole is formed in the center of the silver electrode 30, into which a platinum electrode 32 which will become an anode is inserted, and an epoxy resin is cast around the platinum electrode 32 as an insulating layer 36 and fixed. Furthermore, by drilling a hole in a part of the silver electrode 30, embedding a thermistor as a temperature compensating electrode 34 therein, and fixing the whole with epoxy resin as an insulating layer 36, a hole is formed as shown in FIG. It is possible to obtain a hydrogen peroxide electrode unit with a built-in temperature-compensating electrode having the basic structure. FIG. 4 is a sectional view showing a specific structure of the hydrogen peroxide electrode according to the present invention. In this embodiment, an electric wire 46 is connected to the electrode unit shown in FIG. In addition, 50 is O
-It is a ring. The hydrogen peroxide electrode shown in FIG. 4 is manufactured as follows. First, the lead wire 38, which is a molded silver wire, and silver powder are sintered together to form the silver electrode 30. Next, the silver electrode 30
Drill the hole. Meanwhile, the silver lead wire 40 and the platinum electrode 32 are soldered. The silver electrode structure and the platinum electrode structure are primarily cast using epoxy resin 36. Thereafter, the lead wires 38, 40, 42 and the electric wire 46 are soldered. The unit thus constructed, the case 48, and the O-ring 50 are second-molded using epoxy resin 44. Finally, as shown in the figure, the end face is machined to form a spherical surface. The hydrogen peroxide electrode configured in this way has a fourth
The surface of the electrode shown in the figure is tightly coated with an immobilized enzyme (glucose oxidase) membrane and fixed in a measurement cell part (not shown) filled with a phosphate buffer solution of pH 7. In this case, a voltage is applied to the platinum electrode 32 so as to always have a potential difference in the range of +0.6 to 0.8 V with respect to the silver electrode 30. It is assumed that oxygen in the air is dissolved in the buffer solution. Under such conditions, if a hydrogen peroxide electrode is used to measure, for example, glucose concentration in blood, glucose undergoes the following reaction under the action of an immobilized enzyme. As is clear from the reaction formula (1), when measuring the glucose concentration, the oxygen concentration in the buffer solution decreases stoichiometrically. On the other hand, hydrogen peroxide produced by the decomposition of glucose is oxidized at the platinum electrode and reduced at the silver electrode, producing reaction currents as shown in the following equations. By actually measuring the reaction current shown in the above formula (2), the glucose concentration can be converted. The characteristics of the electrode of the present invention will be explained by giving an experimental example in which glucose concentration was determined using the hydrogen peroxide electrode of the present invention based on the measurement method described above. Experimental example Glucose solutions with glucose concentrations of 150 mg/dl and 500 mg/dl are used, and 20μ of these glucose solutions are used.
When injected into the measurement cell, each 8.5nA
and a reaction current of 27.5nA was detected. in this case,
A good linear relationship was observed between glucose concentration and current value, confirming that it is possible to analyze glucose at unknown concentrations. Next, each hydrogen peroxide electrode according to the present invention coated with an immobilized enzyme membrane was placed in a constant temperature water bath for 20 min.
℃, 25℃, and 30℃ in a glucose solution (glucose concentration 15 mg/dl), and calculate the oxidation current value based on the generated hydrogen peroxide using the polarographic method and current-voltage conversion with a built-in temperature compensation circuit. Measured using a measuring device. In this case, the output of the electrode is obtained as a current value (nA) according to the polarographic method,
According to a current-voltage conversion measuring device, it can be obtained as a voltage value (mV). The measured values are shown in Table 1.

[Table] As is clear from Table 1, in the polarographic method, the current value increases significantly as the temperature of the reaction solution increases; According to , the current value shows only a slight increase as the temperature rises. Furthermore, after immersing the electrode of the present invention in a glucose solution, the time required to obtain a constant output value was 20 seconds or less. As is clear from this experimental example, it has been confirmed that the hydrogen peroxide electrode for enzyme electrodes with a built-in temperature compensation electrode according to the present invention has the property of accurately and quickly detecting the temperature of the reaction solution. Ta. As mentioned above, according to the present invention, since the hydrogen peroxide electrode and the temperature compensation electrode are integrated,
The measurement system is simplified and handling operations are also simplified. Furthermore, since the temperature compensation electrode is embedded near the surface of the silver electrode with good thermal conductivity, which measures the reaction current, it is possible to improve the thermal response to temperature drift. Further, according to the present invention, the electrode unit having the above-mentioned structure is connected to an external lead-out wire within a required case, and is fixed by casting resin into the case, thereby providing a temperature-compensated electrode having a rigid structure. A built-in hydrogen peroxide electrode for enzyme electrodes can be easily obtained. Note that the hydrogen peroxide electrode for enzyme electrodes according to the present invention can of course be widely used in clinical chemistry analysis and environmental analysis, and its use can also be expanded to the fields of organic analysis and chemical process control. . Although the preferred embodiments of the present invention have been described above, it goes without saying that various improvements and changes can be made without departing from the spirit of the present invention.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional explanatory diagram showing the cell structure of a hydrogen peroxide electrode equipped with a conventional temperature compensation electrode, and Figure 2 is a characteristic diagram showing the relationship between the drift value of the residual current of the hydrogen peroxide electrode and the reaction temperature. 3 is an explanatory cross-sectional view showing the principle structure of a hydrogen peroxide electrode for an enzyme electrode according to the present invention, and FIG. 4 is an explanatory cross-sectional view showing an embodiment thereof. 30...Silver electrode, 32...Platinum electrode, 34...
Temperature compensation electrode, 36...Insulating layer, 38, 40, 4
2...Lead wire, 44...Secondary casting resin, 46...
...Wire, 48...Case, 50...O-ring.

Claims (1)

[Scope of utility model registration request] A cylindrical silver electrode as a counter electrode is provided with a hole in the center thereof, a platinum electrode as a working electrode is inserted through the center hole of the silver electrode, and a hole is formed in a part of the back side of the silver electrode. A temperature compensating electrode such as a thermistor is inserted here, and these platinum electrodes and temperature compensating electrodes are insulated and fixed by casting resin onto the silver electrode to form an electrode unit, and the outer surface of the electrode unit is covered with an immobilized enzyme. A hydrogen peroxide electrode for enzyme electrodes that is closely coated with a membrane.