JPS58189551A - Pretreatment of hydrogen peroxide electrode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is aimed at solving the problem that the activity of a hydrogen peroxide electrode (diaphragm-coated electrode for detecting hydrogen peroxide), which is a type of enzyme electrode using an immobilized enzyme membrane, deteriorates with long-term use. This paper relates to a surface treatment method for improving electrodes that are stable for a long period of time and have high responsiveness.

Enzyme electrodes are integrated with electrodes and have the advantages of being selective, rapid, and accurate, making them suitable for clinical chemical analysis,
Widely used as a minute hand for environmental analysis, etc. The hydrogen peroxide electrode that constitutes the enzyme electrode is used to oxidize hydrogen peroxide produced by the catalytic action of an enzyme with an anode made of platinum, etc., and quantify specific components from the oxidation current value. There is. It is generally desired that this type of electrode has high sensitivity and long life.

To measure the concentration of hydrogen peroxide, platinum is used as an anode,
Most methods use silver as a cathode, measure electrolytic current while applying a constant voltage between both electrodes, and determine hydrogen peroxide by a calibration curve method or calibration method. By applying a potential of 0.6 V or more to the platinum electrode relative to the contact, the electrolytic current becomes rate-limited by the diffusion of hydrogen peroxide. Hydrogen peroxide electrodes based on this measurement method often show a decrease in electrode activity after long-term use. A decrease in activity leads to a decrease in conversion and a deterioration in detection limit capability. If the deterioration is severe, please use the school IE.
The law becomes inapplicable.

An object of the present invention is to provide an electrode surface treatment method that eliminates the above-mentioned drawbacks and provides a more sensitive and stable hydrogen peroxide electrode.

Because a constant potential is always applied to the platinum electrode, deterioration of activity may occur due to the formation of platinum oxide on the surface of the platinum γ node with long-term use, organic matter dissolved in the reaction solution, etc. This is thought to be due to the adsorption of inorganic substances. The inventors focused on this point and discovered a surface treatment method for reducing the decrease in activity of the hydrogen peroxide electrode and providing a long-term stable electrode.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

The hydrogen peroxide electrode of interest is shown in the ts1 diagram.

In FIG. 1, 1 is a platinum electrode as an anode, 2 is an electrode supporting insulator, and 3 is a silver electrode as a cathode.

The platinum electrode 1 is provided at the center of the silver electrode 3. 4 and 5 are lead wires led out from the platinum electrode 1 and the silver electrode 3, respectively. The hydrogen peroxide electrode configured in this manner is used as an enzyme electrode. Note that 7 is a 0-ring. The enzyme electrode shown in FIG. 1A is fixed to a measurement cell (not shown), and a constant voltage in the range of 0.6 to 0.5 volts is applied between the platinum electrode 1 and the silver electrode 3.

A flowchart of the pretreatment method for the hydrogen peroxide electrode is shown in FIG. First, as shown in Figure 1, roughen the surface of the layered electrode with coarse emery paper (approximately
(About 0) (polishing process 11) The ultrasonic cleaning in the next process is an operation to remove particles, dirt, etc. from the surface (ultrasonic cleaning process 12). . Further, in order to remove organic substances on the surface, sufficient degreasing is performed using baking soda (degreasing step 13). Further, ultrasonic cleaning is performed (ultrasonic cleaning step 14), and the electrode surface is immersed in nitric acid to dissolve and remove other metal powders (acid treatment step 15).
).

In addition, in order to reduce the effects of oxides etc. generated during long-term use, the electrodes were immersed in a phosphate buffer (pH 8.5).
Aging is performed using a constant voltage of ~0.8V as the closing force nL (aging step 16). This stabilizes the electrode sensitivity over long periods of use, resulting in a long life.

The present invention will be explained by showing experimental results using a hydrogen peroxide electrode of the type shown in Fig. These are the results of an experiment in which a hydrogen peroxide solution was measured using a polarographic method by attaching it to a reaction cell together with a molecular membrane. @3
As shown in the figure, by performing the pretreatment, good linearity with respect to the hydrogen peroxide solution was obtained. Furthermore, as a result of similar measurements performed using a current-voltage converter, as shown in FIG. 4, excellent linearity was also obtained for the hydrogen peroxide solution.

FIG. 5 shows the response when a hydrogen peroxide solution was injected into the reaction cell section. As shown in Figure 5, the pretreated electrode has an extremely fast response to peroxidation and hydrogen concentration, with a response time of 90 cm.

The time to reach the steady state value of just over 90 inches is within 5 seconds after injection. Figure 6 shows an enzyme (glucose oxidase) immobilized on the electrode! This is the response to a glucose solution when [ is attached (enzyme electrode shown in FIG. 1A). Even when an immobilized enzyme membrane is installed, any glucose concentration (500 m
g/dt, 300mIL/dt, 100mg/dj
) response is very fast, 901 response time is 10
Within seconds. In contrast, the glucose solution (500 mg/cl) of the electrode without pretreatment (baking soda degreasing) in Figure 7
/, , 300 mg/dz, 100 mg/d
j). A comparison between FIG. 6 and FIG. 7 shows that by performing baking soda degreasing, good responsiveness can be obtained even when an immobilized enzyme membrane is attached.

FIG. 8 shows the stability of the activity of the hydrogen peroxide electrode pretreated according to the present invention. Glucose solution 150% with the immobilized glucose oxidase membrane attached
Measurement was carried out in mg/dL, and stability over 3 cycles or more was obtained. Initial values were reproduced by replacing the old immobilized enzyme membrane. If no aging treatment is performed, there will be a large degree of deterioration in the initial stage, and within 3 days the initial value will decrease to about 1/4 to 1
/2, and by aging a hydrogen peroxide electrode that is highly sensitive and stable for a long period of time can be obtained.

By carrying out the method of the present invention, the activity of the hydrogen peroxide electrode for the # element electrode is stabilized, so the number of times the hydrogen peroxide electrode and the immobilized enzyme membrane are replaced can be reduced. This means that the hydrogen peroxide electrode and the immobilized enzyme membrane can be used effectively.Furthermore, the ratio of oxidation current to residual current stabilizes as the activity of the hydrogen peroxide electrode stabilizes, allowing for more accurate substrate detection. and hydrogen peroxide can be quantified.

The diaphragm-coated electrode for hydrogen peroxide detection is used for clinical chemistry analysis.

Although it is widely used for environmental analysis, we can expect its development in the fields of organic chemical analysis and chemical process control. The method of the invention also applies to other materials such as gold.

It can also be applied to electrodes made of palladium. The same applies to oxide electrodes.

As explained above, the pretreatment method for a hydrogen peroxide electrode according to the present invention includes a polishing step of polishing the electrode surface of the hydrogen peroxide electrode, and an ultrasonic cleaning process to remove dirt adhering to the electrode surface. a degreasing step to remove organic matter etc. adhering to the electrode surface, an acid treatment step to remove metal powder etc. adhering to the electrode surface, and stabilization of the activity of the electrode. By including an aging step for increasing the temperature, a more sensitive and stable hydrogen peroxide electrode can be provided.

In addition, in the flowchart of FIG. 2, the degreasing step may be performed after the acid treatment step.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of a hydrogen peroxide electrode, the general figure is a schematic cross-sectional view of an enzyme electrode, Figure #I2 is a flowchart of the pretreatment method of the present invention, and Figures 3 to 8 are FIG. 3 is a characteristic diagram showing experimental results for explaining effects. 1... Platinum electrode, 2... Insulator, 3... Silver electrode,
5... Immobilized #membrane. ;r1 7zl! l zu 3 same me i jy) cfta CPPM) f 4 Fig. 0 3θ 6θ V time 〔8-〕 f 7m21 Sho Seki [Second-]

Claims (1)

[Claims] 1) a polishing step of polishing the electrode surface of the hydrogen peroxide electrode;
An ultrasonic pre-cleaning process to remove dirt adhering to the electrode surface, a degreasing process to remove organic matter etc. adhering to the electrode surface and degreasing, and metal adhering to the pre-electrode surface. A peracid electrode characterized by comprising an acid treatment step for removing powder etc. and an aging step for stabilizing the activity of the electrode, and an anode provided insulated at the center of the silver electrode. A pretreatment method for a hydrogen peroxide electrode comprising a platinum electrode. 3) In the pretreatment method described in claim 1 or wc2, the polishing step is characterized by roughening the electrode surface with coarse emery paper and then finishing with fine emery paper. 611 treatment method for hydrogen peroxide electrode. 4) Percentage Fraud In the pretreatment method described in any one of claims 1 to 3, the degreasing step is performed using baking soda. . 5) In the pretreatment method according to any one of claims 1 to 4, the acid treatment step is performed by immersing the electrode surface in nitric acid. Processing method. 6) In the pretreatment method according to any one of claims 1 to 5, the aging step is performed by immersing the electrode in a phosphate slow cocoon solution and applying a predetermined voltage to the electrode. A method for pretreating a hydrogen peroxide electrode, characterized by: