JP2001208721A - Oxygen electrode - Google Patents

Abstract

(57) [Problem] To provide an oxygen electrode capable of measuring oxygen easily, accurately, and quickly without being affected by impurities. SOLUTION: An oxygen electrode in which a polydialkylsiloxane film is provided on a substrate electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen electrode for accurately and rapidly measuring an oxygen concentration.

[0002]

2. Description of the Related Art As an oxygen electrode for measuring the oxygen concentration in an aqueous solution, that is, the dissolved oxygen concentration, oxygen permeability,
Clark-type oxygen electrodes that utilize a hydrophobic diaphragm are known. In the Clark-type oxygen electrode, an aqueous electrolyte solution (internal electrolyte) is filled in a support on which a cathode and an anode are fixed,
By covering the cathode surface with an oxygen-permeable, hydrophobic membrane, oxygen from the external aqueous solution reaches the cathode surface,
Mixing of the internal electrolyte and the external aqueous solution is prevented. Oxygen that has reached the cathode surface is reduced here and provides a reduction current. Since there is a correlation between the reduction current value and the oxygen concentration in the external solution, the oxygen concentration in the external aqueous solution is determined based on a calibration curve created in advance.

The Clark-type oxygen electrode has a structure in which an oxygen-permeable and hydrophobic Teflon (registered trademark) membrane or the like is adhered to a support on which a cathode and an anode are fixed, so that the dimensions are inevitably large. Become something. Usually, a columnar shape having a cross section of several mm or more in diameter is commercially available. In addition, a complicated operation of attaching a diaphragm on (around) the cathode is required.

[0004] Miniaturization of electrodes for measuring dissolved oxygen,
In order to simplify the structure, a method in which a metal or carbon electrode is directly inserted into an aqueous solution to be measured without using a membrane can be considered. However, in this case, if reducing compounds are present in the sample, they are reduced on the electrode, giving an excessive reduction current response compared to the value expected from the oxygen concentration. In addition, if there are adsorptive substances in the sample, these are adsorbed on the electrode surface and reduce the effective surface area of the electrode,
The response current is reduced. That is, it is difficult to measure the oxygen concentration in an aqueous solution containing various components such as a body fluid with a metal or carbon electrode that does not use a diaphragm.

[0005] In order to solve these problems, it has oxygen permeability, has a function of suppressing permeation of hydrogen peroxide, other reducing compounds, and adsorptive compounds, and is easily manufactured on an electrode. It is necessary to search for and use materials that can form films. However, such a functional film material has not been found.

[0006]

Under such circumstances, the present inventor has used a material which has oxygen permeability and which can suppress the permeation of hydrogen peroxide and the like and which is easy in film forming operation. The purpose of the present invention is to provide a micro-sized oxygen electrode easily.

[0007]

The present inventors have made various studies to overcome the above-mentioned drawbacks of the conventional oxygen electrode. As a result, the polydimethylsiloxane-based polysiloxane was formed on the electrode surface using water as a dispersion medium. It was found that the electrode formed by drying after application to the electrode could satisfy the above object, and based on this finding, the present invention was accomplished. That is, the present invention
(1) An oxygen electrode characterized by providing a polydialkylsiloxane film on a substrate electrode, and (2) a polydialkylsiloxane dispersion liquid is applied to a substrate electrode and dried. (1) It is intended to provide a method for producing an oxygen electrode as described in the above item.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The material of a substrate electrode used in the present invention is not particularly limited.
Precious metals such as platinum and gold or carbon-based materials are advantageously used. The method of applying the polydialkylsiloxane dispersion used in the present invention is not particularly limited, and the substrate medium is covered with an appropriate amount of the dispersion by a dip coating method, a spin coating method, a casting method, etc., and then the dispersion medium is evaporated. It may be dried. Examples of the substituted alkyl group of the polydialkylsiloxane used in the present invention include those having 1 to 5 carbon atoms, specifically, polydimethylsiloxane, polydiethylsiloxane, polydipropylsiloxane, polydibutylsiloxane, and polydipentylsiloxane. The alkyl group is preferably a lower alkyl group having 1 to 2 carbon atoms. Polydialkylsiloxane is
It is dispersed in an appropriate solvent and applied on the electrode surface. As a dispersion medium, water, alcohol, acetone or the like is used, and water and alcohol are particularly preferable.

In the present invention, the concentration of the polydialkylsiloxane in the dispersion is appropriately determined according to the film forming method to be employed and is not particularly limited, but is usually 2% by weight.
Above. In the present invention, the polydialkylsiloxane film formed on the substrate electrode has a function of suppressing the permeation of hydrogen peroxide and the adsorptive compound. And preferably 1 to 10 μm. If this is too thin, the effect is not sufficient, and if it is too thick, oxygen permeability may be hindered.

Next, an example of the embodiment of the present invention will be described in detail. First, after pretreatment such as polishing of a substrate electrode,
An oxygen electrode is obtained by immersing in a polydimethylsiloxane dispersion and drying. It is inserted into a sample solution containing an appropriate electrolyte together with a counter electrode, a reference electrode and the like, and has an appropriate potential with respect to the reference electrode, for example, a potential of −0.1 to −0.3 V when the reference electrode is a silver-silver chloride electrode. , And a current is recorded, a correlation is found between the reduction current value obtained and the oxygen concentration, and the oxygen concentration can be determined from the current value.

In this method for producing an oxygen electrode, there is no difficulty in producing the oxygen electrode even if a minute electrode having a diameter of millimeters or less is used as a substrate electrode. The thickness of the polydialkyl siloxane film can be arbitrarily controlled. In particular, by forming a thin film having a thickness of 10 μm or less, an oxygen electrode capable of rapidly responding to a change in oxygen concentration can be obtained.

[0012]

Next, the present invention will be described in more detail with reference to examples. Example 1 (Preparation of Polydimethylsiloxane Membrane-Coated Electrode and Oxygen Response, Hydrogen Peroxide Response Test) As shown in FIG. 1, only end face 1 was exposed and the side face was insulated with glass 2 (diameter 1.6 mm). ) Was polished with 0.05 μm diameter alumina powder and washed with water to obtain a substrate electrode. After immersing the end face 1 of the electrode (actually, the end face of the insulating material and platinum) 1 in a 5% (w / v) polydimethylsiloxane dispersion, immediately lift it up and place it in the air at room temperature with the platinum end face up. And left to dry for 4 hours to obtain a polydimethylsiloxane-coated electrode. The thickness of the polydimethylsiloxane on the electrode was about 10 μm.

The electrode coated with the polydimethylsiloxane film is used as a working electrode, a platinum wire as a counter electrode, a silver-silver chloride electrode as a reference electrode, and a phosphate buffer solution (pH 25, temperature: 25 ° C.) having a concentration of 0.1 mol / liter. After inserting and connecting a constant voltage power supply (trade name, Hokuto Denko HA-150) and a function wave generator (trade name, Hokuto Denko HB-104), and passing oxygen gas to remove oxygen in the liquid, , The working electrode +
The potential was scanned at a rate of -0.01 V / sec from 0.4 V to -0.4 V to record a current-potential curve (linear sweep voltammogram). After recording the linear sweep voltammogram of the above, and further performing the same linear sweep voltammogram recording in a buffer solution containing 0.1 mmol / L of hydrogen peroxide after argon bubbling and deoxygenation, the potential and the current were measured. FIG. 2A) is a graph showing the relationship. In the figure, the dotted line, solid line, and broken line indicate that the polydimethylsiloxane membrane-coated electrode in Example 1 of the present invention was tested for (a) argon ventilation, zero hydrogen peroxide concentration, (b) air ventilation, and peroxide. It is a graph showing the relationship between the electric current and electric potential obtained on the condition of zero hydrogen concentration, and (c) the conditions of argon ventilation and the concentration of hydrogen peroxide of 0.1 mmol / liter. As is apparent from FIG. 2a), the current obtained under the condition of air ventilation and zero hydrogen peroxide (b), that is, the reduction of oxygen, was smaller than the current obtained under the condition (a) of argon ventilation and zero hydrogen peroxide concentration. Current rises from a potential of +0.1 V (vs. silver-silver chloride electrode),
An almost constant value (-0.15 mA / cm ² ) is given in a potential region lower than 0.1 V (vs. silver-silver chloride electrode). On the other hand, when hydrogen peroxide was added under the conditions of argon ventilation (c), the current applied was not much different from the current under the condition of zero hydrogen peroxide concentration.

Reference Example 1 (Oxygen response and hydrogen peroxide response test on platinum electrode) Only the end face shown in FIG. 1 was exposed, and the end face of platinum (1.6 mm in diameter) whose side face was insulated with glass was 0 mm in diameter. .05 μm
A platinum electrode polished and washed with alumina powder is used as a working electrode,
In the same manner as in Example 1, (a) Argon ventilation, zero hydrogen peroxide concentration condition (b), air ventilation, hydrogen peroxide concentration zero condition, and (c) argon ventilation, hydrogen peroxide concentration 0.1 Graphs showing the relationship between the potential and the current when the linear sweep voltammogram was recorded under three conditions of mmol / liter are shown in FIG. 2b) by dotted lines, solid lines and broken lines, respectively, as in FIG. 2a). As is clear from FIG. 2b), the current obtained under the condition of air ventilation and zero hydrogen peroxide (b), that is, the reduction of oxygen, compared to the current obtained under the condition (a) of argon ventilation and zero hydrogen peroxide concentration. Was almost the same as the result of Example 1.
That is, the voltage rises from a potential of +0.1 V (to silver-silver chloride electrode) and gives a substantially constant value (-0.15 mA / cm ² ) in a potential range lower than -0.1 V (to silver-silver chloride electrode). ing. On the other hand, the current applied when hydrogen peroxide was added under the condition of argon ventilation (c) was significantly different from that of Example 1, and was higher than the current under the condition of zero hydrogen peroxide concentration by potential +0.2 V (From the silver-silver chloride electrode), and gave a substantially constant value (-0.06 mA / cm ² ) in a potential region lower than -0.1 V (with respect to the silver-silver chloride electrode). Comparing the results of Example 1 and the results of Reference Example 1, the current response to oxygen hardly changed even when the working electrode surface was coated with a polydimethylsiloxane film, whereas the current response to hydrogen peroxide was almost completely changed by coating. It was found to be completely suppressed.

Test Example 1 (Test for Measuring Oxygen Concentration on Polydimethylsiloxane Film-Coated Electrode) The polydimethylsiloxane film-coated electrode prepared in Example 1 was used as a working electrode, a platinum wire was used as a counter electrode, and a silver-silver chloride electrode was used as a reference electrode. And inserted into a phosphate buffer solution (temperature 25 ° C.) having a pH of 7 and a concentration of 0.1 mol / liter, and a constant voltage power supply (Hokuto Denko H.)
A-150) and set to a potential of -0.3 V (to silver-silver chloride electrode). The buffer was stirred with magnetic stirring. Argon and oxygen were passed through the buffer at different ratios, and the oxygen concentration was determined by a dissolved oxygen meter (trade name, Biot) using a commercially available Clark-type oxygen electrode. FIG. 3 is a graph showing the relationship between the current value obtained with the polydimethylsiloxane film-coated electrode and the oxygen concentration obtained using a dissolved oxygen meter. As is clear from FIG. 3, the two are in a linear relationship, indicating that the present polydimethylsiloxane film-coated electrode can be used as an oxygen electrode for determining the dissolved oxygen concentration. When uric acid and serum albumin, which are known as body fluid components, were added to a buffer solution under air saturation at a concentration of 0.1 mmol / L and 0.1 mg / mL, respectively, the current of the polydimethylsiloxane membrane-coated electrode was increased. Did not show any change.

[0016]

The oxygen electrode of the present invention can easily be miniaturized and can measure the oxygen concentration quickly. According to the method for manufacturing an oxygen electrode of the present invention, an oxygen electrode having such excellent performance can be manufactured by simple steps, and the thickness of the film can be easily controlled. The oxygen electrode of the present invention is used in the fields of medical measurement, fermentation process management, food management, environmental measurement, and the like.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one example of a substrate electrode used in an embodiment of the present invention, with a part thereof being omitted.

FIG. 2 is a graph showing oxygen response and hydrogen peroxide response of a polydimethylsiloxane film-coated electrode or a platinum electrode in Example 1 and Reference Example 1. In a), a dotted line, a solid line, and a dashed line indicate that the electrode coated with the polydimethylsiloxane film in Example 1 of the present invention was tested (a) argon ventilation, zero hydrogen peroxide concentration, (b) air ventilation, Conditions of zero hydrogen oxide concentration,
And (c) is a graph showing the relationship between current and potential obtained under the conditions of argon ventilation and a hydrogen peroxide concentration of 0.1 mmol / liter. In b), a dotted line, a solid line, and a dashed line are obtained with the unmodified platinum electrode in Reference Example 1, respectively.
The current and potential obtained under the conditions of zero hydrogen peroxide concentration, (b) air ventilation, zero hydrogen peroxide concentration, and (c) argon ventilation, 0.1 mmol / liter hydrogen peroxide concentration 5 is a graph showing the relationship of.

FIG. 3 is a graph showing oxygen responsiveness of an oxygen electrode in Test Example 1. 4 is a graph showing a relationship between a current value and an oxygen concentration obtained with a polydimethylsiloxane film-coated electrode in Test Example 1 of the present invention.

[Explanation of symbols]

 1 end face 2 glass 3 platinum wire end face

Claims (2)

[Claims] 1. An oxygen electrode comprising a substrate electrode and a polydialkylsiloxane film provided on the substrate electrode. 2. The method according to claim 1, wherein a polydialkylsiloxane dispersion is applied on the substrate electrode and dried.
The method for producing an oxygen electrode according to the above.