JPS59182357A - Ion sensor - Google Patents

Abstract

PURPOSE:To obtain an ion sensor having excellent durability by constituting an ion sensitive membrane of a thin plasma polymerized high polymer film incorporated therein with an ion exchange group. CONSTITUTION:A silver electrode plate 14 is set in a vacuum vessel, and is subjected to glow discharge in a chloromethyl styrene atmosphere to form a thin plasma polymerized film of chloromethyl styrene in the central part on the one side of the electrode 14. Such electrode is immersed in a dehydrated triethyl amine to convert the chloromethyl group to a quaternary ammonium. The rear side and edge of the electrode are then masked with silicone rubber 15, so that the base surface of the silver and a liquid to be detected do not contact with each other in the stage of measurement. The ion sensitive membrane 6a constituted in such a way consists of the high polymer membrane having a high degree of crosslinking and high density and high adhesion to the base material of an ion sensor and therefore the membrane has high durability with less adsorptivity of protein, etc.

Description

[Detailed description of the invention] (b) Industrial application field The present invention relates to an ion sensor.

More specifically, it can be manufactured easily and with stable quality,
In particular, the ion-selective chamber rj of the coachite wire type (
The present invention relates to an ion sensor suitable as a small ion sensor such as a CW-SK) or an ion sensor using a field effect transistor (hereinafter referred to as a 5-FET).

(B) Prior Art Conventionally, electrochemical measurement methods have been used to analyze various dissolved components in general samples and biological samples, and various ion sensors sensitive to various ions are known.
However, these ion sensors had various problems.

In other words, if we talk about chloride ion sensors, for example, Ag/
There are chlorine ion selective electrodes that use AgO/ system solid electrodes and solid electrodes made by mixing Ag0A' with a matrix such as silicone rubber and using them as membrane electrodes, but these are highly contaminated by organic matter in living organisms such as proteins. It has the disadvantage of Another example is a chloride ion selective electrode using a liquid ion exchanger, but this is impractical because it is a liquid membrane. On the other hand, a chloride ion selective electrode using an ion exchange membrane as an ion sensitive material has improved characteristics and has improved the drawbacks of the above electrodes. but,
These membranes are cut out or molded into thin films from ion exchange resin to form an ion-selective electrode as shown in Figure 1 having an internal electrode (in the figure, (1) is the ion exchange membrane, (2) is the internal electrode,
(3) shows the internal liquid junction solution, (4) shows the electrode tube, and (5) shows the lead wire), but the ion-sensitive membrane is directly coated on the metal electrode. a
It is difficult to apply it to an ion sensor such as W-SE, and it is also difficult to form it on a solid surface such as glass, which is often used as a sensitive surface of the substrate of an ion sensor. In other words, in order to form an ion exchange membrane on such a solid surface, operations such as dissolving the ion exchange resin in a solvent and applying it are necessary, but in this case, sufficient adhesion cannot be obtained and durable ion It was difficult to form an exchange membrane, and it was also difficult to control the membrane thickness, making it impossible to obtain an ion sensor with stable characteristics.

On the other hand, recently, pH-sensitive 5-FIT, in which a pH-sensitive film made of ceramics such as tantalum oxide is coated on the gate of a field-effect transistor, has been used, but it provides ion sensitivity other than pH sensitivity. In order to
It is necessary to form a desired ion-sensitive film on this sensitive surface or on the gate of the FET, which has the same problems as described above.

(c) Purpose of the Invention This invention was developed in view of the above-mentioned conventional problems, and uses a polymer membrane as an ion-sensitive membrane. One of the objectives is to provide an ion sensor with excellent durability.

The inventors of this invention focused on the possibility of forming a highly cross-linked, high-density polymer film on a solid surface with good adhesion through plasma polymerization, and as a result of intensive research, they discovered that this plasma-polymerized polymer film could be formed using plasma polymerization. By forming it on the sensitive surface of an ion sensor substrate such as a metal electrode, glass, or ceramic, and introducing an ion-sensitive group such as an ion-exchange group into the polymer membrane, it can respond sufficiently to the intended ions and be durable. This invention was achieved by discovering the fact that an excellent ion sensor, especially a chloride ion sensor, can be obtained.

B) Structure of the Invention Thus, according to the present invention, there is provided an ion sensor in which an ion-sensitive membrane is formed on the sensitive surface of an ion sensor substrate having a sensitive surface such as a metal electrode, a glass membrane, or a ceramic. An ion sensor is provided in which the membrane is made of a plasma polymerized polymer membrane into which ion exchange groups have been introduced.

The plasma-polymerized polymer membrane into which ion-exchange groups have been introduced can be formed by forming the plasma-polymerized polymer membrane on the sensitive surface of the ion sensor substrate and then introducing the desired ion-exchange groups through chemical treatment. Often, monomers with the desired ion exchange groups may be formed directly by subjecting them to plasma polymerization conditions. In particular, in the case of a chloride ion sensor, a quaternary ammonium group is suitable as the ion exchange group to be introduced. It may be introduced by contact treatment, or it may be introduced by contact treatment with tertiary amine after forming a plasma-polymerized polymer film using a monomer having a chloromethyl group.■Quaternary ammonium They may also be introduced by direct plasma polymerization using monomers having groups. In the case of a cation sensor, a sulfonate group can be mentioned as the ion exchange group to be introduced, but in the same way as above, it can be introduced by contact treatment with sulfuric acid or sulfuric acid gas after the formation of a plasma polymerized membrane, or by using a monomer having a sulfonate group. It can also be produced in the same way by directly introducing it.

When introducing ion exchange groups after forming a plasma polymerized film,
As monomers for plasma polymerization, it is possible to use compounds that do not have polymerizable functional groups, usually vinyl aromatic compounds such as styrene, methylstyrene, divinylbenzene, etc., as well as easily converted into desired ion exchange groups. It is appropriate to use derivatives of these having a functional group (for example, the above-mentioned chloromethylated product). As the monomer having an ion exchange group in advance, for example, a long-chain alkyl ammonium salt can be used. Moreover, two or more types of these monomers may be used.

On the other hand, the ion exchange group of the present invention includes various ion exchange groups that can be sensitive to a desired ion. For example, when a chloride ion sensor is intended, a niquaternary ammonium group, lower alkyl substituted ammonium chloride, etc. If a cation sensor is intended, a sulfonate group may be introduced and selected appropriately, and these treatment methods include various methods such as normal wet treatment and dry treatment that are applied to the production of general ion exchange membranes. can be applied.

Various methods can be used to perform plasma polymerization, and it is usually appropriate to place the ion sensor substrate in a monomer atmosphere under high vacuum and subject it to so-called low-temperature plasma polymerization using glow discharge. From the viewpoint of film uniformity and adhesion, it is preferable to apply discharge conditions of low solid wave (several KH4 or less). At this time, by appropriately adjusting the discharge time, the thickness of the υ polymer membrane can be controlled with high precision, and an ion-sensitive membrane of stable quality can be obtained.

Incidentally, the thickness of the sensitive film of the present invention is, for example, that of S-FET.
When used as an ion electrode, it is preferably about 1000 to 1500X, and when used as an ion electrode, it is about 0.01 to 1μ.
m is preferred.

Examples of the ion sensor substrate include various materials having a solid surface such as metal, glass membrane, ceramic, etc. as an ion-sensitive surface. For example, by using a metal electrode such as platinum or silver as an ion sensor base material and coating it with the plasma polymerized polymer membrane of the present invention, a CW-EIE as shown in FIG. 2 can be obtained (in the figure, (7) is a metal electrode, and (6) is a plasma-polymerized polymer membrane into which a desired ion exchange group has been introduced). By forming an ion-selective field effect transistor (Step 5-F), it is possible to measure desired ions as shown in FIG.
B'I') can be obtained [in the figure, (9) is 510
2. Gate of Si3N4 etc., QO is drain part, α℃
1, (9), Q indicate the source part and the brocade indicates the silicon base.
O, α9 and @ constitute a field effect transistor (FIT). The fabrication of such a 5-FET is described, for example, in °' J, Appl, phys, 49.5.
8 (1980) and Masayuki Matsuo et al. °°. ]. However, in some cases, pH-sensitive membranes such as tantalum oxide or other pH-sensitive membranes may be used.
- A plasma-polymerized polymer film may be formed on the sensitive surface of the NET.

Furthermore, as shown in FIG. 4, an ion sensor substrate having a glass membrane αJ on the sensitive surface and an internal electrode may be used as an ion-selective electrode, and various other ion sensor substrates may also be used. I can do it.

The ion sensor of the present invention thus obtained has durability because its ion-sensitive membrane is composed of a polymer membrane with a high degree of crosslinking, high density, and excellent adhesion to the ion sensor substrate. It is an excellent product, and contamination with proteins and the like hardly occurs. Furthermore, its responsiveness is also good.

Therefore, it is useful as a sensor for measuring various ions such as chloride ions, and is especially useful as a small sensor such as Of-Engineering SE and 15-FET because it is easy to manufacture and has excellent quality reproducibility. be.

candy) Examples Example 1゜A silver electrode plate (5 x 1 run) was placed in a vacuum container with a discharge electrode.
), the pressure was reduced to approximately 9.8 torr, and then chloromethylstyrene was introduced through the monomer inlet tube extending into the vacuum vessel, and a glow discharge (I KH2, 50mA) was generated in an atmosphere of 1 torr of monomer vapor. .

600 V) to form a plasma-polymerized polymer thin film of chloromethylstyrene at the center of one side of the silver electrode. The silver electrode was removed and immersed in dehydrated triethylamine for 15 hours at room temperature to convert the chloromethyl group into quaternary ammonium. Next, the back side and edges of this electrode were coated with silicone rubber (Shin-Etsu Silicon K) 1C445.
By masking with T) to prevent contact between the silver background and the test liquid during measurement, as shown in Figure 5,
A small chlorine ion sensor was obtained. In addition, in the figure, C4
) is the silver electrode, 19 is the silicone rubber layer 3, (6a) is the fourth
This figure shows a plasma-polymerized polystyrene thin film into which grade ammonium groups have been introduced.

Using this ion sensor, a sodium chloride aqueous solution (#
Figure 6 shows the results of investigating the responsiveness using Na as a sample (!J is a special grade reagent and water is distilled deionized water) at 120°C and 10° to 10'-5N. In addition,
As a comparison electrode, a reference electrode using Ag/Ag, C1 as an internal electrode and a saturated potassium chloride aqueous solution as an internal liquid junction solution was used.

In this way, good linearity was obtained in the chlorine ion concentration range of 10' to 1O-1 mol, and the slope was 52 mV.
/decacLe (20℃, theoretical value 58.1 mV/
aecacLe) and ivy.

Further, the results of determining the selection coefficients (Kcj'-i values) for various interfering substances by the chlorine ion sensor are shown in the table below. Note that the interfering ion concentration was fixed at 1X10''-''N and determined by the mixed solution method.

Further, although the above chlorine ion sensor was immersed in water for two months, no peeling of the sensitive membrane was observed and the responsiveness was unchanged from before immersion.

Example 2 A plasma-polymerized polymer thin film was formed on a silver electrode in the same manner as in Example 1 except that styrene was used instead of chloromethylstyrene.
(A chloromethyl group was introduced by immersion in a mixed solution of 313 and tetrachloroethane, and a quaternary ammonium group was introduced by further treatment in dehydrated triethylamine in the same manner as above, and a similar chloride ion sensor was obtained. .

(f) Effects of the Invention As can be understood from the above explanation, the ion sensor of the present invention has excellent practical durability and has low adsorption of proteins, etc., and is useful for a variety of applications. be.

In particular, the formation of the ion-sensitive membrane does not require coating treatment and can be easily performed with good quality reproducibility, so it is suitable for small and ultra-small ion sensors such as CW-SE and 5-PET, as well as chloride ion sensors. It is useful as

[Brief explanation of the drawing]

Fig. 1 is a structural diagram illustrating a conventional ion-selective electrode using an ion exchange membrane, Figs. 2 to 4 are structural diagrams illustrating the ion sensor of the present invention, and Fig. 5 P). , (B) show another ion sensor of the present invention, (A) is a plan view, (O) is a longitudinal section, and FIG. 6 shows ion responsiveness using the ion sensor of FIG. This is a graph showing. (1)...Ion exchange membrane, (2)...Inner electrode,
(3)... Internal liquid junction solution, (4)... Electrode tube,
(5)... Lead wire, (6)... Plasma polymerized polymer membrane, (7)... Metal electrode, (9)...
Gate, αO...drain part, 0t...source part, 0...silicon base, α3...glass film, α station...silver electrode, (151...silicon rubber layer,
(6a)...Plasma polymerized polystyrene thin film. Figure 7 Figure 2

Claims (1)

[Claims] 1. An ion sensor formed by forming an ion-sensitive membrane on the sensitive surface of an ion sensor substrate having a sensitive surface such as a metal electrode, a glass membrane, or a ceramic, the ion-sensitive membrane comprising:
An ion sensor characterized by being made of a plasma-polymerized polymer membrane into which ion exchange groups have been introduced. 2. The ion-sensitive membrane is formed by subjecting the ion sensor substrate to plasma polymerization in a monomer atmosphere to form a polymer membrane, and then introducing a desired ion exchange group into the polymer membrane, or by introducing a desired ion exchange group into the polymer membrane. The ion sensor according to claim 1, which is formed by plasma polymerization in an atmosphere of a monomer having a group. 3. A patent in which the ion-sensitive membrane is formed by subjecting an ion sensor substrate to plasma polymerization in a monomer atmosphere to form a polymer membrane, and then introducing a desired ion exchange group into the polymer membrane. The ion sensor according to claim 1. 4. The ion sensor according to claim 2 or 3, wherein the plasma polymerization is performed under low frequency discharge conditions of several KH2 or less. 5. The ion sensor according to claim 2 or 3, wherein the monomer is styrene, methylstyrene, divinylbenzene, or chloromethylstyrene. 6. The ion sensor for measuring chloride ions, wherein the ion exchange group is a quaternary ammonium group.