JPH0384449A - Ion sensor and sensor plate - Google Patents

Abstract

PURPOSE:To improve a water-holding property without using a flocculation preventive agent, such as agar, by using the hydrous jelly of the metal salt of a non-flocculating polyacrylic acid and forming a gelatinous member for the internal liquid of electrodes. CONSTITUTION:Silver layers 2a, 2b and silver chloride layers 3a, 3b are laminated on copper electrodes 1a, 1b of a paper and polyester substrate 1 and the gelatinous member 4 formed by using the jelly of the metal salt of the non- flocculating polyacrylic acid is screen-printed on the silver chloride layer 3a in the state of directly dissolving the internal liquid for the electrodes or the salt into the hydrous jelly; thereafter, an ion sensitive film 5 is provided to form a dam body 6. The hydrous jelly of the metal salt of the polyacrylic acid which does not flocculate even when the internal liquid or salt is directly dissolved is used as the gelatinous member 4 in such a manner and, therefore, the good water-holding property is maintained over a long period of time without using other gelatinizing agents, such as agar. Since the concn. and viscosity of the internal liquid are thereby prevented from changing for a long period of time, the specified potential and characteristics of the electrodes are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion sensor using a gel-like member retaining an internal electrode solution or salt as an electrode, and a sensor plate as a component thereof.

[Conventional technology]

To measure the pH of a solution, for example, a pH-responsive glass membrane electrode is used, which typically involves blowing molten glass of a special composition onto the tip of a glass support tube to form a hollow sphere. It is constructed by enclosing, as an internal solution, a buffer solution having a pH of around 7 mixed with a potassium chloride solution saturated with silver chloride, and an internal electrode having a silver chloride layer formed on the surface of the silver rim.

In addition, the reference electrode is an electrode that always maintains a constant potential even if the composition of the sample liquid to be measured changes, and like the glass membrane electrode described above, the reference electrode has the same internal liquid and the internal electrode is a support tube made of glass. A through hole is provided at the tip of the support tube, and this is filled with an inorganic porous biological material or a porous organic material, or a glass sleeve is used to allow the internal fluid to flow out. A liquid junction is formed to flow out, and the sample liquid and the internal liquid come into contact to maintain electrical connection.

However, these pH-responsive glass membrane electrodes and reference electrodes have problems such as large-sized devices, poor productivity, and the need to store them by immersing them in an appropriate solution.

In order to solve these problems, a plate-type electrode for ion measurement was developed in which the internal liquid was fixed on the electrode.

In this case, to fix the internal fluid, agar, gelatin,
By mixing a gelling agent such as glue or alginic acid with a moisture evaporation inhibitor such as glycerin or ethylene glycol, a gel-like material for the internal liquid is created, which is heated to form a paste and then applied onto the electrode. is screen printed.

[Problem to be solved by the invention]

However, the conventional gel-like material used in the above-mentioned plate-type electrode has poor water retention properties, and the moisture content may be depleted or become excessively wet depending on the atmosphere during use or storage, so that the internal liquid This causes a problem in that the concentration changes, significantly lowering reliability.

In order to improve this water retention, a water-containing jelly containing an acrylic polymer as a main component, specifically U Jelly (manufactured by Showa Denko@, trade name), was dissolved in an aqueous solution consisting of internal liquid, etc., and agar or gelatin was added. A gel-like member made into a gel by adding a gelling agent such as

However, while U-jelly alone has excellent water retention, when salt is added, the molecular chains of the acrylic polymer aggregate, releasing the retained water and resulting in a decrease in water retention. Therefore, it is necessary to use a gelling agent such as agar or gelatin in combination to form a gel-like member.

In this case, the number of components increases, and not only does it require mixing operations, but it is also difficult to completely prevent the agglomeration of the molecular weight of the acrylic polymer, so it is desirable to further improve reliability. It is rare.

By the way, the ion sensor for measuring ion concentration is for measuring the ion concentration in the sample liquid as described above, but it is used to measure the ion concentration in the sample liquid. A so-called ion-sensitive field effect transistor (I5FIET) in which an ion-sensitive film is formed is also used.

This l5FII! T utilizes the fact that when an ion-sensitive membrane is brought into contact with a sample liquid, the conductivity near the semiconductor surface changes in response to changes in the electric field generated at the interface between the ion-sensitive membrane and the solution, and this is detected by an external circuit. It has been made possible.

In this 15FET, a separate gate electrode is provided not on the semiconductor substrate on which the PUT is formed, but on another insulating substrate, an ion-sensitive membrane is provided on this, and a separate comparison electrode is provided facing each other to make it an independent component. A so-called separated gate type 15FEτ, which is used by connecting the FET to an FET, is also known.

In order to stabilize the electrode and improve the reliability of these 15FETs and separated gate type 15FETs, it is preferable to fix an internal electrode solution or a gel-like member in which salt is dissolved to the electrode. The question of what to use as this gelling agent is similar to the above-mentioned problem.

The purpose of the present invention is to use a water-containing jelly that has good water retention properties and does not cause aggregation even when used alone or in combination with an internal solution or salt, without using agar or the like, and thereby provides a highly reliable electrode. An object of the present invention is to provide an ion sensor having the following features.

[Means to solve the problem]

In order to solve the above problems, the present invention provides an ion sensor in which a field-effect semiconductor can detect a sensitive value of a sample liquid using a gate electrode and a reference electrode coated with an ion-sensitive membrane. A gel-like member obtained by dissolving a solution or salt in a water-containing jelly is fixed to at least one of the gate electrode and a reference electrode, and the internal solution for the electrode or the salt is directly dissolved in the water-containing jelly. Electrical work using non-agglomerating polyacrylic acid metal salts
The present invention provides an ion sensor characterized by using the following.

In addition, a separate gate electrode and a comparison electrode are provided on an insulating substrate separate from the field-effect semiconductor substrate, and a comparison electrode and a separation gate electrode to be used in connection with the gate electrode of the field-effect semiconductor are provided. A gel-like member in which at least an internal electrode solution or salt is dissolved in a water-containing jelly is fixed to at least one side to form an independent component, and the internal electrode solution or salt is directly melted in the water-containing jelly and non-agglomerated. A sensor plate characterized by using a polyacrylic acid metal salt jelly, and a sensor plate in which the opposing portions of the separation gate electrode and the comparison electrode are surrounded by a wall body, and the separation gate electrode and the comparison electrode are provided with a jelly. The present invention provides a sensor plate characterized in that a partition wall is provided in the sensor plate, and a liquid junction is provided in the partition wall.

Next, the present invention will be explained in detail.

The present invention uses a water-containing jelly of a salt of polyacrylic acid, in which water is bound to the molecules of a metal salt of polyacrylic acid, but the polymer skeleton is non-ionic. Examples include UX-100 (trade name, manufactured by Showa Denko).

The method for producing a gel-like member is to directly dissolve an appropriate concentration of the electrode internal solution or salt in a water-containing jelly such as the above-mentioned ux-ioo, and add a viscosity modifier as necessary to form a gel-like member. .

In addition, depending on the viscosity of the gel-like material prepared, in order to apply the gel-like material to the electrode, it is possible to use screen printing or to form a dam around the electrode in advance to provide a dripping window for the sample liquid. Filling the inside of this embankment body or placing a bottom shaped one in a predetermined shape may be selected as appropriate.In either case, the internal liquid or salt must be fixed on the electrode, so It must be gel-like, that is, semi-solid.

The above-mentioned gel-like member is used for the gate electrode of the 15FET, the separated gate electrode of the separated gate type 15FET, and the comparison electrode, but when used as the comparison electrode, the potential of the comparison electrode changes by keeping the ion concentration constant. without any
It is stable and preferable, and if used between the gate electrode, the separation gate electrode and the ion-sensitive membrane provided thereon,
For example, if a laminated structure consisting of a lower silver layer and an upper silver chloride layer is used for these electrodes, a stable potential can be obtained even if the grain size of the silver chloride particles in the upper layer varies somewhat, and the measured value will be stable. It is preferable.

As the internal liquid for electrodes, for example, Ag/A can be used as a reference electrode.
gCj! For the electrode, a 3.3 molar KC1 solution (A
gCl saturated), Hg/HgzClz electrode, saturated KC1 solution, Hg/Hg2SO4 electrode 0.
5 molar concentration of 112504.

When using a gel-like member, in order to prevent contamination due to diffusion of ions from the sample liquid to the internal liquid and from the internal liquid to the sample liquid, a partition should be provided between the measurement electrode and the reference electrode, and both should be separated. A liquid junction may be provided in which a communicating slit is provided to allow the sample liquid to flow through capillary action and come into contact with the internal liquid, or the slit 7 may be filled with water-containing jelly to form a liquid junction.

[Effect]

Since we used a water-containing jelly of metal salts of polyacrylic acid that does not coagulate even when the internal solution or salt is directly dissolved, it has good water retention because no water is released, and the viscosity decreases little, making it possible to use agglomeration inhibitors such as agar. If water retention is good, there will be little change in the internal solution concentration or salt concentration, the potential will be constant, and the characteristics as an electrode will be constant.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

In Fig. 1, the copper foil adhered to the paper polyester substrate l is polished with a 2 μm diamond slurry to obtain a mirror surface [stylus film thickness meter (thin film surface profiler manufactured by Tencor Co., Ltd.]).
Surface roughness 20 measured by Alpha Step 200>
0 nge), and copper electrodes 1a and 1b of predetermined shapes were formed by photolithography.

Next, the cathode current density was reduced to 0 using a commercially available cyan Yoroku Strike Metsuki bath containing Ig/ and a constant current power supply.
．． 5A/do? The substrate was immersed in the bath for 5 seconds in a state where the substrate was slanted so that the temperature was 0.5 seconds, and after taking it out, it was washed with water. Then, it was immersed in a commercially available cyan electrolytic plating bath containing 20 g/l of silver while maintaining the temperature at 50°C, and the current density was
Electrolytic plating was performed at 12 A/drd for 1 minute and 30 seconds to form 15μ silver layers 2a and 2 on copper electrodes 1a and Ib, respectively.
b was formed.

Then 0. Electrolytically treated in normal (N) hydrochloric acid (HCI) for 2 minutes and 40 seconds using the above substrate as an anode and a platinized titanium membrane as a cathode at an anode current density (0.2 A/drrf), Silver chloride layers 3a and 3b were formed on the surfaces of silver layers 2a and 2b. The surface roughness was 200 nm as measured by the stylus film thickness meter.

In the silver chloride layer 3a, 0X-100100 parts by weight KCj! After screen printing a silver chloride supersaturated gel-like member 4 consisting of 1 part by weight, a resin liquid containing a vinyl chloride-vinyl acetate copolymer as a main component is further applied to cover the ion-sensitive membrane 5.
A bank body 6 was formed of an epoxy resin insulator so as to surround the electrode on which the ion-sensitive film was formed and the silver chloride electrode 3b.

In this way, the silver layers 2a, 2b and the silver chloride layers 3a, 3b are laminated on the copper electrodes 1a, 1b, and the silver chloride layer 3a is provided with an ion-sensitive layer 45, while the silver chloride layer 3b is used as a separate reference electrode. The plate is completed.

Example 2 As shown in FIG. 2, in the same manner as in Example 1, a comparison electrode consisting of a laminated structure of a silver layer and a silver chloride layer, a separation gate electrode, and an ion-sensitive film were formed on the separation gate electrode. A partition wall 16b is provided in the middle of an outer frame 16a having a shape similar to that of the embankment shown in FIG.
The embankment body 16 having a thickness of c is covered with a polypropylene sheet (thickness 0.
5m) and bonded to the substrate 1 using an acrylic adhesive.

Next, the inside of the embankment and partition wall surrounding the tin chloride layer 3b is filled with the same gel-like member 14 as in Example 1, and a polypropylene sheet (thickness 0.2
m) 17 is joined using an acrylic adhesive, and the upper part of the gel-like member 14 is covered and sealed.

In this way, a sensor plate having a separate comparison electrode in which the gel-like member 14 is coated on the silver chloride layer 3b is completed.

Comparative Example (Conventional Example) In Example 1, 0X-ioo 100 parts by weight Ktl 1 part by weight of a silver chloride supersaturated gel-like member, U Jelly 100 parts by weight 3.3N -KCj! A sensor plate was prepared in the same manner except that 40 parts by weight of gelatin and 3 parts by weight of silver chloride supersaturated gel-like material were used.

Measuring the potential of the sensor plate prepared in Example 1.2 and Comparative Example above with respect to the sample liquid using a potential measuring device,
The results of determining the rate of change after 30 days are shown in the table.

From the above results, it can be seen that the rate of change in potential of the sensor plate of the example is significantly smaller than that of the sensor plate of the comparative example using a conventional gel-like member.

〔Effect of the invention〕

According to the present invention, a gel-like member for the electrode internal solution is formed using a water-containing jelly of a metal salt of polyacrylic acid that does not aggregate even when the electrode internal solution or the salt is directly dissolved, and this is fixed to the electrode. The plate-type ion sensor has good water retention over a long period of time without using other gelling agents such as agar, and therefore the concentration and viscosity of the internal solution do not change over a long period of time, and the potential of the electrode remains constant. can give reliable measurements.

[Brief explanation of drawings]

FIG. 1(A) is a plan view of a sensor plate according to one embodiment of the present invention, FIG. 1(B) is a sectional view taken along line I-1, and FIG. , the same figure (b) is the II-II sectional view. In the figure, 1 is a substrate, 2a, 2b are silver layers, 3a, 3b are chloride i1 layers, 4.14 is a gel-like member, 6.16 is an embankment body, 16
c is thrift. August 29, 1999 Figures (a) (b)

Claims (3)

[Claims] (1) In an ion sensor that uses a gate electrode coated with an ion-sensitive membrane and a reference electrode to detect the sensitive value of a sample liquid using a field-effect semiconductor, at least the internal solution for the electrode or the salt is dissolved in a water-containing jelly. A gel-like member formed by the process is fixed to at least one of the gate electrode and the reference electrode, and a non-agglomerating polyacrylic acid metal salt is directly dissolved in the water-containing jelly with the electrode internal solution or salt dissolved therein. An ion sensor characterized by using jelly. (2) A separate gate electrode to be used in connection with the gate electrode of the field-effect semiconductor and a comparison electrode are provided on an insulating substrate separate from the substrate of the field-effect semiconductor, and these separated gate electrodes and the comparison electrode are provided. A gel-like member in which at least an internal electrode solution or a salt is dissolved in a water-containing jelly is fixedly provided on at least one of the parts to form an independent component, and a non-containing part is formed with the internal electrode solution or a salt directly dissolved in the water-containing jelly. A sensor plate characterized by using cohesive polyacrylic acid metal salt jelly. (3) The opposing portions of the separation gate electrode and the comparison electrode are surrounded by an embankment, a partition wall is provided between the separation gate electrode and the comparison electrode, and a liquid junction is provided in the partition wall. The sensor plate according to claim 2.