JPS6130208Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite ion sensor comprising an ion sensor consisting of a gate-insulated field effect transistor having a sensor gate and a liquid junction type comparison electrode.

Conventionally, as this type of ion sensor, one having a structure shown in FIG. 1, for example, is known. In the figure, reference numeral 1 denotes a P-type silicon substrate, and an N-type drain 2 and a sensor source 3 are formed on this substrate 1.
is formed. 4, 5, and 6 are the common drain layer 2, the sensor source 3, and each electrode portion of the silicon substrate 1, and 7 is the sensor gate portion, the cross section of which is shown in FIG.

As is clear from FIG. 2, the gate part 7 has a double structure of a silicon oxide layer 8 and a silicon nitride layer 9 formed on the silicon substrate 1, and the sensor gate part 7 has, for example, an ion-sensitive layer. Layer 10 is coated.

The ion sensor having the above configuration is immersed in the test liquid 12 in the container 11 together with the comparison electrode 13, as shown in the circuit of FIG. A positive potential of a voltage line Vd is connected to the drain 2 of the ion sensor, and a constant current circuit 14 is connected to the source 3 to operate as a source follower circuit. Then, the change in conductivity at the semiconductor surface under the gate insulating film due to the interfacial potential between the gate insulating film of the ion sensor and the test liquid and the change in the interfacial potential at this time are extracted as the source potential Vs. Since this source potential Vs has a linear relationship with the logarithm of the ion concentration, the ion concentration of the test liquid can be measured by measuring this Vs.

The present invention provides a compact and easy-to-manufacture composite ion sensor that integrates the above-mentioned ion sensor and reference electrode.

An embodiment of the composite ion sensor of the present invention will be described below with reference to the drawings. 4 and 5 are explanatory diagrams of a composite ion sensor, in which double tubes 17, 1
The tip of the internal tube 17 constituting 8 is made of resin 19
The other end is closed with a rubber stopper 20 to form an electrolyte chamber 21 for sealing an electrolyte inside the tube. Further, a liquid junction means 22 is provided in the resin 19 to communicate the electrolyte chamber and the test liquid. An electrode 23 is fluid-tightly inserted into the electrolyte chamber 21 from the side wall of the tube to form a comparison electrode.

The material for the internal tube 17 is glass;
Polyamides such as nylon 6, nylon 11, and nylon 12, polyester, polyethylene, polypropylene, silicone resins, and the like can be used. The liquid junction means 22 can be filled with fibers, porous ceramics, etc., but a method of embedding hollow fibers of polymer that is easily wetted in resin is preferred as it can be easily applied to very thin catheters. . Such hollow fiber polymers include cellulose, cellulose acetate, ethylene vinyl alcohol copolymer, etc. Among these, ethylene vinyl alcohol copolymer is particularly thermoplastic, and its cross-sectional area can be freely adjusted by press pressure. This is preferable because it can be done. The internal liquid sealed in the electrolyte chamber 21 may be any aqueous solution containing chloride ions, but is usually a KC aqueous solution or
An aqueous NaCl solution is used. In particular, a saturated KC solution is preferred because of its good conductivity and low temperature dependence, and physiological saline is preferred in order to reduce the liquid junction potential difference in the living body. Electrode 23
Ag/AgC is preferable in terms of stability.An insulating tube 18 is further placed on the outside of the reference electrode formed in this way, and an ion sensor≒ is embedded between the inner tube 17 and the outer tube 18 at the tip. . This ion sensor has a wide horizontal shape and a very thin thickness of 100 to 200 μm, so the outer tube can be chosen with a thin wall and the increase in the outer diameter of the sensor will be minimal.

The material of the outer tube 18 may be glass, polymer, metal, or rubber as shown in the case of the inner tube 17. Particularly desirable are water-resistant rubbery substances (isoprene rubber, urethane rubber, silicone rubber, etc.). Among them, it is particularly elastic,
Silicone resin is preferable because it reduces the space between the outer and inner tubes and maintains the elasticity of the tube.A method of coating such an outer tube with an inner tube is to coat the tip of the inner tube with silicone resin. This can be obtained by fixing the ion sensor, protecting the FET electrode with an insulating material, and then covering it with a shrink tube, or by covering it with a tube expanded with a solvent and then shrinking it by heating or evaporating the solvent. (or
(External tubes may be made using DipCoat, Mold, etc.) At this time, by making the resin at the tip of the internal tube thinner, it is possible to prevent an increase in the thickness of the electrode portion of the ion sensor. This thinning can be done by heating the tip of the internal tube and pulling it, or by cutting the tip of the reference electrode after preparing the end of the reference electrode as shown in Figure 5. .

The composite electrode thus produced is connected to a connector. The connector 24 is connected to a lead wire 25 connected to the ion sensor and a lead wire 26 connected to the electrode of the comparison electrode. At this time, for the reference electrode, make a hole in the inner tube and use adhesive 2.
It is best to seal it with 7. In addition to this, it is desirable to provide a guard electrode. The guard electrode may be formed by passing a suitable conductor such as a silver wire or copper wire between the outer tube and the inner tube, and exposing the tip to the measuring liquid, or by depositing it on the FET. The resins 19 and 27 are preferably epoxy resins, silicone resins, or a combination of both. The composite ion sensor manufactured in this way can be used immediately without forming bubbles or precipitated salts at the liquid junction by storing it in a tube containing the internal liquid through a sealed stopper fixed to the other end of the sealed tube. state.

〔Example〕

The inner tube 17 is a nylon 11 tube with an inner diameter of 0.6 mm and an outer diameter of 1 mm, and the electrode 23 is a tube made of nylon 11 with an inner diameter of 0.6 mm and an outer diameter of 1 mm.
Ag/AgC wire, length 7mm width as ion sensor
Using a FETPH sensor with a thickness of 0.5mm and 150μ, silicone rubber with an inner diameter of 0.7mm and a wall thickness of 0.1mm is swollen in hexane and is covered with silicone rubber, which is swollen in hexane, then dried and shrunk to form a 16G elastane needle with an outer diameter of 1.2mm. We were able to obtain a composite PH sensor that can be inserted into the system and has excellent stability and durability.

As described above, the composite ion sensor of the present invention has the reference electrode and ion sensor located very close to each other, so close electrical contact between the two is maintained and there is no measurement error caused by AC interference or noise, resulting in a compact composite ion sensor. This made it possible to provide an ion sensor.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the structure of the ion sensor, Fig. 2 is a sectional view of the gate part of the ion sensor, Fig. 3 is an electric circuit diagram using the ion sensor, and Figs. 1 is a sectional view showing an example of a composite ion sensor of the present invention. 7...Sensor gate, 17...Internal tube 1
8... External tube, 21... Electrolyte chamber, 22...
...liquid junction means, 23...electrode.

Claims (1)

[Scope of utility model registration request] Both ends of the internal tube 17 constituting the double tubes 17 and 18 are sealed to form an electrolyte chamber 21 inside the tube, and a liquid junction means 22 for communicating the chamber and the measuring liquid is connected to a sealed portion at the tip of the tube. and a reference electrode formed by liquid-tightly inserting the electrode 23 into the chamber, and a lead wire 25 to each electrode 4, 5, 6 of the ion sensor consisting of a gate insulated field effect transistor having a sensor gate 7. The sensor gate is positioned at the tip of the inner tube to seal the end of the gap formed by the double tube, and the lead wire is connected to the outer tube 18 and the inner tube 17. A composite ion sensor consisting of an ion sensor connected to a connector through a gap.