JP3395408B2 - Electrode for electrochemical measurement - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for electrochemical measurement, which is used for electrochemical measurement such as voltammetry and chronoamperometry and which has good manufacturing reproducibility and is inexpensive.

[0002]

2. Description of the Related Art Electrochemical measurement methods such as voltammetry and chronoamperometry can perform highly sensitive and highly accurate analysis with a relatively simple device configuration, and compared with optical methods such as colorimetric analysis It is not easily affected by turbidity and is widely used in research and quality control analysis. One of the important factors that regulate the sensitivity in such an electrochemical measurement is the area of the electrode sensitive part. As a method of controlling this area, an electrode of a type in which a solid conductor wire made of metal or carbon is covered with a hydrophobic polymer material and only its end face is in contact with a solution is used.

In recent years, there are many examples in which the electrode thus produced is applied to continuous flow analysis, that is, flow injection analysis and liquid chromatography.

[0004]

In such a case, the pressure applied to the electrode is relatively large as compared with the case of the batch type in which the electrode is usually immersed in the solution for the measurement, and the gap between the electrode and the insulator, etc. When the solution leaks from the electrode, there may occur a problem that the area other than the sensitive surface of the electrode end face comes in contact with the liquid and the electrode area changes, or a leak current flows from the lead wire. In the example of the electrode for amperometric measurement, it seems that the base current shows a high value when the solution leaks. Therefore, it was difficult to determine whether the base current was increased due to the electrode sensitive portion being contaminated or the electrode itself was a defective product.

Further, when the electrodes are attached to the flow type analyzer, a cell structure capable of withstanding a certain amount of back pressure is required, and a sealant made of polymer resin or an O-ring is often used. In such a cell structure, placing the electrode sensitive surface at an accurate position is important for ensuring the reproducibility of the measurement result. An object of the present invention is to provide an electrode for electrochemical measurement having a configuration in which the solution does not leak from a gap or the like of the components of the electrode assembly as described above and the electrode sensitive surface can be set at an accurate position. To do.

[0006]

According to the present invention SUMMARY OF THE INVENTION The electrochemical measurement electrodes, solid conductors for a cylindrical electrode having a connection portion, said solid conductor is inserted therein, the cylindrical outer surface of the solid conductor hydrophobic polymer material made of the tube that is integrated with said solid conductor and fixed to the inner peripheral cylindrical surface thereof in a watertight manner, the said tube body is integrated with the solid conductors adjustably by the connecting portion inserted into, it comprises an outer tube, made of polymeric material fixed in a watertight hydrophilized outer cylindrical surface and by filling the adhesive in the gap of the peripheral cylindrical surface thereof of the tube body.

It is preferable that the connection portion of the solid conductor is made of a metal conductor. The outer cylinder may be made of a hydrophobic polymer material, and the inner peripheral cylindrical surface thereof may be hydrophilized. It is more preferable that the solid conductor and the pipe body are filled with a low-viscosity adhesive between them and fixed.

[0008]

In order to obtain the electrode for electrochemical measurement that achieves the above object, the inventors have coated the solid conductor wire with a hydrophobic polymer material and sealed it in an insulating outer cylinder. I tried to manufacture an electrode for electrochemical measurement by filling it with an adhesive, but in such a configuration, it may not be possible to completely prevent the occurrence of liquid leakage as described above, and the electrode yield No rise,
It has been a cause of rising costs. As a result of detailed investigation and examination of such a liquid leakage situation, it was found that liquid leakage occurred from the cracks in the adhesive filled in the gap between the hydrophobic polymer material and the insulating outer cylinder.

It has also been found that it may be possible to prevent liquid leakage from the gap between the solid conductor wire and the hydrophobic polymer material by side-polishing the linear solid conductor and then coating it with the hydrophobic polymer material. It was However, this method was considered to be poor in work efficiency and poor in economic efficiency. Therefore, as a result of further study, a solid conductor for a cylindrical electrode having a connecting portion, and a solid conductor were inserted inside, and the outer peripheral cylindrical surface and the inner peripheral cylindrical surface of the solid conductor were watertightly fixed to each other. A tubular body made of a hydrophobic polymer material that is integrated with the tubular body that is integrated with the solid conductor is inserted into the tubular body so that the position of the tubular body can be adjusted by the connecting portion, and the outer cylindrical surface of the tubular body that has been hydrophilized Electrode for electrochemical measurement equipped with an outer cylinder made of a polymer material that is filled with an adhesive and fixed in a watertight manner in the gap between the inner peripheral surface and the inner peripheral surface does not cause liquid leakage as described above and is efficient. It turned out to be an electrode that can be produced.

Since the outer cylindrical surface of the hydrophobic polymer material that coats the solid conductor is hydrophilized, cracks do not occur in the adhesive filled between the outer cylinder and the adhesive strength can be increased. it can. Further, since the solid conductor is inserted into the outer cylinder by the connecting portion of the solid conductor so that the position of the solid conductor can be adjusted, the position of the end of the solid conductor, which becomes the electrode sensitive surface, can be adjusted to a desired position.

By making the connecting portion of the solid conductor made of a metal conductor, the connecting portion has low flexibility, and the position can be adjusted more precisely. When the outer cylinder is made of a hydrophobic polymer material and the inner peripheral cylindrical surface is hydrophilized, the insulating property of the outer cylinder of the electrode is further improved, and the adhesiveness with a solid conductor or the like can be kept good. When the solid conductor and the pipe are fixed by filling a low-viscosity adhesive between them, the water tightness and durability of the pipe and the solid conductor are further improved.

Solid conductors for electrodes include platinum wire, gold wire,
A wire rod made of various metals such as titanium wire or a conductor formed of carbon or the like is formed into a cylindrical shape. Fluorine resin is used as the hydrophobic polymer material used as the material of the tubular body and outer cylinder,
Silicon resin, olefin resin, etc. are mentioned. Further, as the polymer material for the outer cylinder, vinyl chloride resin, acrylic resin and the like can be mentioned. The selection of these resins is made according to various conditions such as the type of liquid actually contacting the electrode, temperature, pH and the like. Also, various adhesive materials are selected according to the selection result of these resins. The adhesive used here includes epoxy-based adhesives, silicone-based adhesives, natural rubber-based adhesives, acrylic adhesives, etc. Among them, epoxy-based adhesives are preferable because they are easy to handle and have high water resistance. Examples of the low-viscosity adhesive include α-cyanoacrylate-based, epoxy-based, and natural rubber-based adhesives. Among them, a low-viscosity α-cyanoacrylate adhesive is preferable because it has good permeability and is easy to handle.

[0013]

EXAMPLES Examples of the electrochemical measurement electrode of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an embodiment of the electrochemical measurement electrode of the present invention. Most of the electrodes have a length of several tens of mm and an outer diameter of about several tens of mm. In the figure, as a solid conductor, a low-flexible copper wire 2 is joined by spot welding to a cylindrical platinum wire 1 having a diameter of 2 mm. Here, the low-flexibility copper wire 2 is cut into an approximate length in consideration of the size and position adjustment of the outer cylinder. Next, the low-flexibility copper wire 2 and the male-threaded plug 3 made of tin-plated iron material are joined by spot welding.

With the platinum wire 1 and the low-flexibility copper wire 2 forming the connecting portion and the male threaded plug 3 joined together, the area before the thread portion of the male threaded plug 3 is covered with a fluororesin tube 4. Then, the platinum wire 1 and the fluororesin tube 4 are completely adhered by heating at 160 ° C. for 30 minutes in an electric furnace to fix them in a watertight manner. The outer surface 4a of the fluororesin tube 4 is hydrophilized with a fluororesin adhesion treatment agent. Subsequently, an epoxy-based resin is formed in the gap between the inner surface 5b of the methacrylic resin-made cylindrical outer cylinder 5 on which the female thread processing 5a is applied, the integrated platinum wire 1, the low-flexibility copper wire 2, and the male screw plug 3. The adhesive 6 is filled, and the position of the tip surface 1a of the platinum wire 1 is adjusted to a desired position by appropriately turning the male screw plug 3, and then the adhesive is cured by heating in an electric furnace at 120 ° C. for 60 minutes. .

Next, the tip end surface 1a of the platinum wire 1 is smoothed with a file and a No. 1500 emery paper. The electrode thus constructed can usually be used as a working electrode of an electrochemical measurement electrode. Also, a reference electrode is prepared by similarly using a silver wire having a diameter of 2 mm instead of the platinum wire 9 having a diameter of 2 mm, and then performing silver chloride treatment.

As described above, the detecting portion of the flow measuring apparatus can be constructed by using the working electrode using the platinum wire and the reference electrode using silver chloride, and using the conductive pipe for the counter electrode. Fifty working electrodes and fifty reference electrodes were produced by the above method, and the base current values were measured for a total of 100 electrodes. All the electrodes had low base current values and were stable.

The reason why such a low base current is stably obtained is that the components such as the platinum wire, the fluororesin tube, and the outer cylinder are fixed and adhered to each other because of the above configuration. Is sufficiently performed, and it is possible to prevent liquid leakage into the electrode. As described above, it was confirmed that the electrode for electrochemical measurement having such a configuration can be easily and reproducibly manufactured without requiring any experience.

In this embodiment, a solid conductor for electrode, that is, a platinum wire 1, a low-flexibility copper wire 2 and a male screw plug 3 integrated with the solid conductor for an electrode are fixed to an outer cylinder 5 by a screwing structure, and further, an adhesive is used. Since the fixation is strengthened by, even if a large high pressure is applied to the tip surface 1a of the solid conductor when measuring a high pressure liquid, liquid leakage or the like is less likely to occur.
Furthermore, it is more preferable that the space d between the platinum wire 1 and the fluororesin tube 4 is filled with the α-cyanoacrylate adhesive 16 and the adhesive is cured so that the both are better watertightly fixed. When such a low-viscosity adhesive material is used, even if the outer cylindrical surface of the platinum wire 1 has a small scratch, the platinum wire 1 can be removed from the gap between the outer surface of the platinum wire 1 and the fluororesin tube 4 without polishing the surface. Liquid leakage can be prevented.

[0019]

EFFECT OF THE INVENTION The electrode for electrochemical measurement according to the present invention has no leakage of the solution from the gaps between the constituents, the electrode sensitive surface can be set at an accurate position, and a low base current value can be obtained. Became.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of an electrochemical measurement electrode of the present invention.

[Explanation of symbols]

1 platinum wire 2 Low bending copper wire 3 Male screw plug 4 Fluororesin tube 5 outer cylinder

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Claims (4)

(57) [Claims] 1. A solid conductor for cylindrical electrode having a connection portion, said solid conductor is inserted therein, the cylindrical outer surface of the solid conductor and the said solid conductor fixed to the inner peripheral cylindrical surface thereof in a watertight manner hydrophobic polymer material made of the tube body are integrated, the solid conductors and the tube body is integrated by inserting therein to adjustably by the connecting portion, which is hydrophilized of the tube outer An electrode for electrochemical measurement, comprising an outer cylinder made of a polymer material, which is watertightly fixed by filling an adhesive between the cylindrical surface and the inner peripheral cylindrical surface. 2. The electrode for electrochemical measurement according to claim 1, wherein the connection portion of the solid conductor is made of a metal conductor. 3. The electrode for electrochemical measurement according to claim 1, wherein the outer cylinder is made of a hydrophobic polymer material, and the inner peripheral cylindrical surface of the outer cylinder is hydrophilized. 4. The electrode for electrochemical measurement according to claim 1, wherein the solid conductor and the tubular body are fixed by filling a low viscosity adhesive between them.