JP2000035414A - Reference electrode for analysis device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a yield of a reference electrode having stable performance. SOLUTION: In this reference electrode, a core material 3 is held by tube parts 13, 15 of a resin case 1 manufactured by resin injection molding, while an internal liquid 2 is sealed within the resin case 1. A flow rate of the internal liquid 2 is controlled by a slit 5 formed between the tube parts 13, 15. An electrode 4 is fixed to a side wall of the resin case 1. The core material 3 is made of a hydrophilic porous polyethylene which is excellent in a hydrophilic property and machinability, while a flow path 31 is formed at the center of the core material 3. When a measuring liquid is passed through the flow path 31 with a working electrode overlapped on the reference electrode, the internal liquid 2 reaches the flow path 31 by a capillary phenomenon so that the working electrode and the reference electrode are electrically connected. In this state, the measuring liquid is analyzed by measuring a potential difference between the reference electrode and the working electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference electrode of an analyzer, and more particularly, to a reference electrode of an analyzer having a stable performance and a high yield.

[0002]

2. Description of the Related Art FIG. 7 is an explanatory view showing the structure of a conventional reference electrode. This reference electrode 500
It is used for double junction type analyzers. The reference electrode 500 is made of a glass tube 501 having a small diameter, and a ceramic core material 502 is attached to the tip thereof. Tube 501
Inside, an internal liquid 503 is sealed. Internal liquid 503
Are, for example, potassium chloride, ammonium nitrate, and lithium acetate. The tip of the reference electrode 500 is fixed to a block 505 that forms a flow path 504.
The distal end of the reference electrode 500 and the flow path 504 are connected by a horizontal flow path 506, and the diameter of the flow path 506 is small in the middle.

[0003] An electrode 507 is attached to the rear end of the tube 501. Further, a pipe 508 is connected near the tip of the reference electrode 500. The pipe 508 is connected to a bottle 510 of the internal liquid 503 via a solenoid valve 509. On the other hand, a working electrode 600 is attached above the reference electrode. Ceramic core material 502
Are manufactured by sintering. The tube 501 has a core material 502 attached to the tip, and is manually heat-formed. Internal liquid 503
Is injected after the tube 501 is formed. After the injection of the internal liquid 503, the pipe 501 is heated to perform a sealing process of the internal liquid 503.

Next, the operation of the reference electrode 500 will be described. The measurement liquid flows from above the channel 504. The measurement liquid is, for example, serum, urine, or a dialysis sample. Also,
The solenoid valve 509 is operated to introduce the internal liquid 503 into the flow path 506 at the tip of the reference electrode. Reference electrode 50
At 0, the internal liquid 503 permeates through the ceramic core material 502 and slowly flows out of the tube. The internal liquid 503 passes through the small-diameter flow path 506 and reaches the flow path 504 in which the measurement liquid flows. Thus, the working electrode 600 and the reference electrode 500 are electrically connected. The measurement liquid can be analyzed by measuring the potential difference between the working electrode 600 and the reference electrode 500.

[0005]

However, in the above-mentioned conventional reference electrode 500, since ceramics is used for the core member 502, it is difficult to manufacture a uniform material, and as a result, the performance of the reference electrode 500 becomes unstable. There was a problem. Also, the reference electrode 50
For example, the manufacturing process is complicated and the yield is low because the glass is used as a material for the ceramics 0 and a ceramic sintered body is used.

Accordingly, the present invention has been made in view of the above, and an object of the present invention is to provide a reference electrode having stable performance and a good yield.

[0007]

In order to achieve the above object, a reference electrode of an analyzer according to the present invention is characterized in that a flow path for flowing a measurement liquid from a working electrode side, an internal liquid is sealed, and an electrode is provided. A resin case having one end buried in the internal liquid and the other end exposed to the outside, a hydrophilic porous polyethylene interposed between the flow path and the resin case, and moving the internal liquid in the resin case to the flow path. It is provided with.

[0008] The internal liquid in the case is carried to the flow channel side by the capillary action of the hydrophilic porous polyethylene. When the internal liquid reaches the measurement liquid in the flow path through the hydrophilic porous polyethylene, the electrode buried in the internal liquid and the working electrode are electrically connected. Therefore, the measurement liquid can be analyzed by measuring the potentials of both electrodes. In addition, by using a hydrophilic porous polyethylene that can be manufactured more homogeneously than conventional ceramics, measurement variations can be suppressed. Furthermore, since the case is made of resin, it is easy to manufacture and the yield is good.

The reference electrode of the analyzer according to a second aspect of the present invention contains a cylindrical hydrophilic porous polyethylene having a flow path through which a measurement liquid flows from the working electrode side, and the hydrophilic porous polyethylene. And a cylindrical portion having a slit in a part thereof, and a resin case in which the cylindrical portion is integrally formed and the internal liquid is sealed around the cylindrical portion,
An electrode having one end buried in the internal liquid in the resin case and the other end exposed to the outside of the case.

[0010] The internal liquid in the resin case reaches the hydrophilic porous polyethylene housed in the cylindrical portion while the flow rate is adjusted by the slit. The internal liquid is conveyed to the channel formed in the hydrophilic porous polyethylene by the capillary action of the hydrophilic porous polyethylene. Thus, the electrode buried in the internal liquid and the working electrode are electrically connected. Therefore, the measurement liquid can be analyzed by measuring the potentials of both electrodes. In addition, by using a hydrophilic porous polyethylene that can be manufactured more homogeneously than conventional ceramics, measurement variations can be suppressed. Furthermore, since the case is made of resin, it is easy to manufacture and the yield is good.

According to a third aspect of the present invention, in the reference electrode of the analyzer, the slit is provided in a direction perpendicular to the axial direction of the cylindrical portion, and the slit width is set to 2 mm or less. It is.

As a result of the experiments by the inventors, the width of the slit was set to 2
It was found that the life of the reference electrode can be maintained long when the thickness is set to be equal to or less than mm. In particular, it was found that when the slit width was 0.5 mm or less, the life of the reference electrode was kept very long. The variation of the measured values in this range was within the allowable range. Therefore, the slit width is 2 m
m, the life of the reference electrode can be kept long.

According to a fourth aspect of the present invention, there is provided the reference electrode of the above-mentioned analyzer, wherein the hydrophilic porous polyethylene has an average molecular weight of about 300,000 in the reference electrode of the above-mentioned analyzer.

[0014] The inventors of the present invention conducted a comparative experiment between the case where the average molecular weight was 3,000,000 and the case where the average molecular weight was 300,000.
In the case of one million, the variation of the measured value exceeded the allowable range. On the other hand, when the average molecular weight was 300,000, the variation in the measured value was within the allowable range. This was true in any case where the slit width was within the above range. Therefore, by setting the average molecular weight of the hydrophilic porous polyethylene to about 300,000, stable measurement with little variation can be performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. The present invention is not limited by the embodiment. FIG. 1 is an assembly view showing the structure of the reference electrode of the present invention. FIG.
FIG. 2 is a cross-sectional view of the reference electrode shown in FIG. The reference electrode 100 has a structure in which the internal liquid 2 is sealed by a two-part resin case 1. The upper case 11
A tubular portion 13 having side walls and fixing the core material 3 is formed at the center of the ceiling portion. An electrode fixing hole 14 for inserting and fixing the electrode 4 is provided on the side wall. The lower case 12 is provided with a cylindrical portion 15 for fixing the core material 3 at the center thereof as described above. The upper case 11 and the lower case 12 are made by injection molding of a resin.

When assembling the upper case 11 and the lower case 12, the core material 3 is inserted into one of the cylindrical portions 13 (115) in advance. In a state where the upper case 11 and the lower case 12 are assembled, a slit 5 is formed between the upper case 11 and the lower case 12. Width A of slit 5
Is 0.5 mm. This slit 5 allows the internal liquid 2
To control the flow rate. When the slit width is reduced, the resistance increases, but the life of the reference electrode 100 increases. When the slit width is increased, the resistance is reduced, but the life of the reference electrode 100 is shortened. These may be set according to the purpose. After assembling the upper case 11 and the lower case 12, the internal liquid 2 is introduced from the electrode fixing hole 14. Then, the electrode 4 is attached and the internal liquid 2
Is enclosed. As the internal liquid 2, an aqueous potassium chloride solution and a water-soluble polymer solution thereof are used. The water-soluble polymer used here is not particularly limited as long as it is used for thickening. Examples thereof include polyvinylpyrrolidone, carboxymethylcellulose, polyvinyl alcohol, and polyethylene glycol. The electrode 4 has a structure in which an electrode rod 42 made of Ag / AgCl is provided on a central axis of a resin support 41 having a piece shape. The electrode 4 is manufactured together with the electrode rod 42 by resin molding.

As the core material 3, a hydrophilic porous polyethylene excellent in hydrophilicity and workability is used. As the hydrophilic porous polyethylene, for example, Sunfine AQ (AQ-800
Asahi Kasei Kogyo Co., Ltd. trade name). The average molecular weight of the hydrophilic porous polyethylene is preferably 300,000. This hydrophilic porous polyethylene is
It is suitable as a core material because it has good water wettability and high water absorption.
In addition, it is characterized in that it can be easily processed into a predetermined shape by machining, and that dirt in serum is hardly adsorbed. In addition, a flow path 31 is provided at the center of the core material 3.

The core material may be a hydrophilic porous polymer in addition to the hydrophilic porous polyethylene.

FIG. 3 is a simplified explanatory view showing a use state of the reference electrode 100. Reference electrode 10
The working electrode 200 is overlapped on the upper part of 0, and the flow channel 31 is matched. Next, the measurement liquid is caused to flow through the flow channel 31. On the other hand, the internal liquid 2
Reaches the flow channel 31 by capillary action of the hydrophilic porous polyethylene. The flow rate of the internal liquid 2 at this time is
Is controlled by Thereby, the working electrode 200 and the reference electrode 100 are electrically connected. In this state, the potential difference between the reference electrode 100 and the working electrode 200 is measured, and the measurement liquid is analyzed.

[Selection of Slit Width] The relationship between the slit width A and the life of the reference electrode 100 will be described. The inventors have determined by experiments that there is no slit and that the slit width A
Is 2 mm, 1 mm, and 0.5 mm, the lifetime of the reference electrode 100 is experimentally obtained. FIG. 4 shows the experimental results. The vertical axis represents the ClB potential (measured potential when the working electrode 200 is chlor), and the horizontal axis represents the number of samples. In this experiment, the life of the reference electrode 100 is defined as the time when the ClB potential becomes about 100 mV. FIG. 9A shows the result when there is no slit (flow path length: 7 mm). In this case, the ClB potential was close to 100 mV when about 20,000 samples were used, and the life was reached.

FIG. 2B shows the result when the slit width A is 2 mm. In this case, the life of the reference electrode 100 has reached about 40,000 samples. FIG. 3C shows the result when the slit width A is 1 mm, and FIG. 3D shows the result when the slit width A is 0.5 mm. When the slit width A is 1 mm, the life of the reference electrode 100 has reached about 60,000 samples. Slit width A is 0.5m
In m, the life has expired at about 80,000 samples. According to this experimental result, the smaller the slit width A, the more the reference electrode 1
00 has a longer life. Note that, from the viewpoint of the accuracy of the case, the lower limit of the slit width A is 0.1 to 0.05 mm.

[Selection of Average Molecular Weight of Hydrophilic Porous Polyethylene] In selecting the average molecular weight of hydrophilic porous polyethylene, the inventors measured the same sample 20 times and measured the variation of the value. saw. This measured value is C
V. When there is no variation, CV becomes 0. FIG. 5 is a graph showing the CV for each slit width when the average molecular weight of the hydrophilic porous polyethylene is 300,000. The vertical axis represents CV, and the horizontal axis represents the number of samples. When the allowable range of the CV is set to 0.35, when the average molecular weight is 300,000, when there is no slit 5 (FIG. (A)) and when the slit width A is any (FIGS. (B) to (d)) ) Was within the allowable range, and it was found that stable measurement could be performed. Note that Na, K, and Cl in the graphs represent working electrodes.

FIG. 6 is a graph showing CV when the average molecular weight of the hydrophilic porous polyethylene is 3,000,000. When the average molecular weight is 3,000,000, FIG.
As shown in (d), any of the working electrodes (Na, K, C
Even when 1) was used, the result exceeded the allowable range of CV. It is considered that this is because the average molecular weight of the core material 3 is too high and the reference electrode 100 has a conduction failure. Therefore, the core material 3 has an average molecular weight of 30.
Ten thousand hydrophilic porous polyethylenes have been found to be preferred.

[Comparison between Ceramics and Hydrophilic Porous Polyethylene] In the above configuration, what happens when ceramics are used instead of hydrophilic porous polyethylene as the material of the core material 3? As a result of the experiments by the inventors, the CV of the ceramic core material was 0.5 or more, which exceeded the allowable range. Thus, it was found that hydrophilic porous polyethylene was more suitable for the core material than ceramics.

[0025]

As described above, according to the reference electrode of the analyzer of the present invention (claim 1), the flow path through which the measurement liquid flows from the working electrode side, the internal liquid is sealed, and one end of the electrode is provided. And a hydrophilic porous polyethylene that is interposed between the flow path and the resin case and moves the internal liquid in the resin case to the flow path. Therefore, the electrode and the working electrode are electrically connected to each other via the internal liquid in the hydrophilic porous polyethylene.
Therefore, it is possible to analyze the measurement liquid in a stable state with little variation. Also, since the case is made of resin, it is easy to manufacture and the yield is good.

Next, the reference electrode of the analyzer according to the present invention (Claim 2) comprises a cylindrical hydrophilic porous polyethylene having a flow path through which a measurement liquid flows from the working electrode side, and the hydrophilic hydrophilic polyethylene. A cylindrical portion accommodating the porous polyethylene and partially having a slit; a resin case in which the cylindrical portion is integrally formed therein and an internal liquid sealed around the cylindrical portion; and an internal liquid in the resin case. And the other end is exposed to the outside of the case, so that the internal liquid passes through the slit and hydrophilic porous polyethylene to reach the flow path, and the electrode buried in the internal liquid and the working electrode It becomes electrically conductive. Therefore, it is possible to analyze the measurement liquid in a stable state with little variation. Also, since the case is made of resin, it is easy to manufacture and the yield is good.

Next, in the reference electrode of the analyzer according to the present invention (claim 3), a slit is provided in a direction perpendicular to the axial direction of the cylindrical portion, and the slit width is set to 2 mm or less. Long life can be maintained.

Next, in the reference electrode of the analyzer according to the present invention (claim 4), the average molecular weight of the hydrophilic porous polyethylene is set to about 300,000, so that stable measurement with little variation can be performed. it can.

[Brief description of the drawings]

FIG. 1 is an assembly view showing a structure of a reference electrode according to the present invention.

FIG. 2 is a cross-sectional view of the reference electrode shown in FIG.

FIG. 3 is a simplified explanatory diagram showing a use state of a reference electrode.

FIG. 4 is a graph showing a relationship between a slit width and a life of a reference electrode.

FIG. 5: Average molecular weight of hydrophilic porous polyethylene is 30
It is a graph which shows CV for every slit width in the case of ten thousand.

FIG. 6 shows that the average molecular weight of the hydrophilic porous polyethylene is 30.
It is a graph which shows CV in the case of 100,000.

FIG. 7 is an explanatory view showing a structure of a conventional reference electrode.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Reference electrode 1 Resin case 11 Upper case 12 Lower case 13 Cylindrical part 14 Electrode fixing hole 15 Cylindrical part 2 Internal liquid 3 Core material 31 Flow path 4 Electrode 41 Resin support 42 Electrode rod

Claims (4)

[Claims] 1. A flow path through which a measurement liquid flows from a working electrode side, a resin case in which an internal liquid is sealed, one end of the electrode is buried in the internal liquid, and the other end is exposed to the outside. And a hydrophilic porous polyethylene interposed between and for moving the internal liquid in the resin case to the flow path. 2. A cylindrical hydrophilic porous polyethylene in which a flow channel for flowing a measurement liquid from a working electrode side is formed; a cylindrical portion that accommodates the hydrophilic porous polyethylene and has a slit in a part thereof; A resin case in which the cylindrical portion is integrally molded inside and an internal liquid is sealed around the cylindrical portion; and an electrode having one end buried in the internal liquid in the resin case and the other end exposed outside the case. A reference electrode for an analyzer, comprising: 3. The reference electrode according to claim 2, wherein the slit is provided in a direction perpendicular to the axial direction of the cylinder, and the width of the slit is set to 2 mm or less. 4. An apparatus according to claim 1, wherein said hydrophilic porous polyethylene has an average molecular weight of about 300,000.
4. The reference electrode of the analyzer according to any one of items 3 to 3.