JPS61170645A - Ion selective electrode consisting of chemically modified glass film - Google Patents

Abstract

PURPOSE:To obtain an ion selective electrode which responds to various kinds of ions by using a functional glass film formed by fixing an ion sensitive material by chemical bonding to the surface of porous glass as a sensitive film. CONSTITUTION:Known porous high silicate glass is used as the porous glass. The adequate pore size can be selected according to the size of the ion sensitive group to be fixed. About 10-600Angstrom pore sizes are usually preferable. The various shapes of the porous glass are possible. The ion sensitive material is a material which can be stably fixed to the OH group on the surface of the porous glass by forming the chemical bond and is a material having the ion sensitive group. More specifically, the material has a trimethoxysilyl group, triethoxysilyl group, etc. as the group for forming the stable chemical bond on the glass surface and has chelatability such as quaternary ammonium group and sulfonate group as the ion sensitive group.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel ion-selective electrode that uses, as a sensitive membrane, a functional glass membrane in which an ion-sensitive substance is immobilized on the surface of a porous glass through chemical bonds.

Due to the physical properties of the ion-sensitive membrane, the ion-selective electrode
They are broadly classified into solid membrane electrodes and liquid membrane electrodes.

As the ion-sensitive membrane of the solid model ion-selective electrode, for example, single crystals of water-soluble inorganic salts such as silver sulfide and silver hegenide, rare earth fluoride salts, or their powders are pressurized. Molding, semi-molten molding, and polymer membranes such as silico/rubber with poorly soluble salts dispersed are known. Solid membrane electrodes using such sensitive membranes are superior in terms of durability and ease of use, but the target ions are limited to poorly soluble salts and there is limited flexibility in terms of membrane shape. There are disadvantages such as being small.

In addition, among solid film electrodes, glass electrodes that use a special glass thin film as a sensitive film have a wide range of applications as they have excellent responsiveness and selectivity, and can be used in organic solvents. , -H electrodes. However, with the glass electrode, the ions to be measured are practically
In addition to H ions, there is a drawback that the method is limited to a small number of cations such as Na ions and K ions, and a glass electrode that responds particularly to anions has not been obtained. Furthermore, with glass electrodes, it is extremely difficult to manufacture a glass thin film.
In addition, it is easy to break and requires careful handling, and it also has drawbacks such as extremely high membrane resistance.On the other hand, liquid exchange type ion-selective electrodes dissolve the ion-sensitive substance in a polar organic solvent that is difficult to mix with water. This electrode is impregnated and held in a porous polymer membrane, porous ceramics, etc., and used as a sensitive membrane. In such a liquid exchange type electrode, many types of organic solutions of ion association extraction systems can be used as sensitive membranes, so it is said that many types of io:J electrodes can be manufactured to measure various organic and inorganic ions. There are big advantages. However, the structure of the electrode is complicated, the operation is somewhat inconvenient, and the sensitive liquid tends to leak out during measurement.
Furthermore, it has the disadvantage of being easily affected by agitation and water pressure.
Therefore, in order to eliminate the above-mentioned disadvantages while maintaining the advantages of this liquid film, a so-called so-called method in which the sensitive substance is dispersed and retained in a polymer film such as silicone comb, ebogyo resin, lacquer, polyvinyl chloride (PVC), etc. Polymer@hot liquid film electrodes have been developed. These electrodes simplify the structure of the electrode and improve the performance of the liquid film electrode, but the sensitive membrane is easily damaged and easily deteriorates. However, they still have drawbacks such as difficulty in using them in organic solvents.

Furthermore, in recent years, attempts have been made to use ionic polymer materials such as ion exchange resins and ion exchange membranes as ion-sensitive membranes; In these respects, we have not yet achieved anything satisfactory.

In view of the problems of the prior art as described above, the present inventors
As a result of extensive research, we have completed a completely new ion-selective electrode that uses functional glass as a sensitive membrane, in which a sensitive substance is immobilized on the surface of porous glass through chemical bonds.

That is, the present invention relates to a chemically modified glass membrane ion-selective electrode whose sensitive membrane is porous glass on which an ion-sensitive substance is immobilized.

The ion-selective electrode of the present invention uses, as a sensitive membrane, a functional glass in which an ion-sensitive substance is immobilized on the surface of a porous glass by chemical bonding. In conventional ion-selective electrodes that use liquid membranes or polymer membranes as sensitive membranes, the solubility of the sensitive substance in water must be low in order to prevent the liquid sensitive substance from leaking into the measurement solution. The sensitive substances that can be used are limited to those with large molecular weights. It was also necessary for the sensitive substance to have appropriate solubility in organic solvents. In contrast, in the ion-selective electrode of the present invention,
Since the sensitive substance is bonded to the porous glass through chemical bonds, there is no elution of the sensitive substance into the measurement solution, so there are few restrictions on the ion-sensitive substances that can be used, and various ions can be selected depending on the measurement target. It is possible to create a sexual electrode. In addition, with conventional liquid film electrodes, it was difficult to measure the ion concentration in organic solvents because the material of the film was attacked, but the porous glass membrane used in the present invention is stable even in organic solvents. Additionally, it can also be applied to measuring ion concentrations in organic solvents.

In addition, in general, in a liquid film type electrode, the detection limit concentration of the ion to be measured is controlled by the elution of the ion exchanger and its counter ion from the sensitive membrane into the measurement liquid, but in the sensitive membrane used in the present invention, , measurement sensitivity is high because there is no elution of ion exchangers.

Further, in the functional glass membrane of the electrode of the present invention, ion exchange is performed through the micropores in the membrane, so the electrical resistance in the electrolyte solution becomes extremely low.

Therefore, the thickness of the glass film can be increased to about 1 kegff, and the mechanical strength is increased. In addition, in the functional glass membrane of the present invention, the sensitive group can be introduced after processing the porous glass into a desired shape, so the glass membrane can be produced very easily, and the matrix can be easily controlled. It is possible to easily produce a sensitive membrane that is optimal for the target ion.

In the present invention, known porous high silicate glass can be used as the porous glass. The pore diameter may be appropriately selected depending on the size of the ion-sensitive group to be immobilized, but it is usually preferably about 10 to 600 A. The shape of the porous glass is not particularly limited, and various shapes are possible depending on the measurement method and the shape of the electrode. It can be used in a shape such as , etc., but it can also be formed into other parts and used as a flow through t=/l-. In a sensitive membrane using porous glass, the electrical resistance is extremely low, so the thickness of the glass membrane should be 1 to 5 m.
It can be made as thick as possible. Therefore, it is easy to process and has high mechanical strength.

The ion-sensitive substance that can be used in the ion-selective electrode of the present invention is a substance that can be stably immobilized by forming a chemical bond to the OH group on the surface of the porous glass, and has an ion-sensitive group. Specifically, as a group for forming a stable chemical bond on the glass surface, it has a trimethocylyl group, a triethylsilyl group, a trichlorosilyl group, etc., and as an ion-sensitive group, it has a quaternary ammonium group, Examples include those having a sulfonic acid group, a crown ether group, a phosphoric acid group, a dithiocarbatriphosphate group, and other sensitive groups having lactate properties.

Li5 like this! A specific example of what is immobilized on the surface of the sensitized substrate is shown in FIG. Figure 1 (11) and (
In the phrase R, R2 and R3 are hydrocarbon chains, n
-1 to 8. The target ions (-) and (j) are mainly heavy anions, and depending on the target ions, R
・Select R2 and R3 in Figure 1(e).
-3 to 9, $12-1%2t or 3. The ions to be measured are mainly 1flfi cations, and n-type and R2 may be selected depending on the ions to be measured. Figure 1 (→ indicates that the ions to be measured are mainly Cg. Figure 1 (ri) indicates that the ions to be measured are mainly monovalent cations. Figure 1 ψ indicates that the ions to be measured are mainly Cg. In the jg1 diagram (p), the ions to be measured are mainly heavy metal ions.

Among the above-mentioned io:tltA-sensitive substances, R2
When R2 is a methyl group, the hydrophilicity of the surface increases and the selectivity for highly hydrophilic chloride ions increases, while when R2 is an octadecyl group, the hydrophobicity of the surface increases, Selectivity to perchlorate ion, which is a hydrophobic ion, is increased.

The sensitive membrane of the ion-selective electrode of the present invention can be produced, for example, by the following method.

First, porous glass is formed into a desired shape using a known method, and then the glass surface is activated. This can be done by refluxing for about 1 to 10 hours.@When using glass that has been used once or whose surface has become dirty after being left for a long time, reflux it for about 1 to 10 hours. 1-2 at around 500”C
It is preferable to decompose and remove organic substances and the like attached to the surface by heating for about a period of time.

After activation, after sufficiently drying the porous glass molded body, the molded body is immersed in a solvent containing the substance to be fixed,
Refrigerate for about 1-10 hours. As a solvent, toluene
Methanol, bovine silane, aceto:tolyl, etc. can be used, and the concentration of the immobilized substance is preferably about 1 to 20%. After refluxing in the fixing substance solution, the porous glass is sufficiently washed and dried to obtain the sensitive membrane used in the present invention.

The ion-selective electrode of the present invention uses the above-mentioned sensitive membrane, and its form is not particularly limited, and it can be any of various known forms of the ion-selective electrode.The ion-selective electrode of the present invention uses the sensitive membrane described above. A representative example of the implementation is shown in FIG. 2 (4), (
b), (t) and shown in FIG.

In Fig. 2, (-), <b> and (1), (1) is a modified glass membrane, (2) is an internal electrode, (3) is an internal standard solution, (4) is a glass tube, (5) (6) is a conductive film (thin film of metal or carbon) attached to a modified glass film, (6) is a lead wire, (
7) is the lead wire coating @ As shown in Figure 2 (A), when connecting the lead wire directly to the sensitive film, one side of the sensitive film is coated with metal or conductive paint. After imparting conductivity, the lead wires may be joined. In the ion-selective electrode of the present invention, the porous glass used as the substrate of the sensitive membrane has excellent workability, so the decorated electrode can be
It has a thin wire shape and can be used as a micro T:/cer. Furthermore, as shown in Figure 3, a porous glass formed into a tubular shape with an ion-sensitive group immobilized thereon can be used as a sensitive membrane.
-t:J? - can be used as an electrode for measuring ion concentration in a flow system. In Figure 3, (8) is a plastic body such as acrylic resin, Teflon, Tyflon, etc., (9) is a tubular modified glass membrane,
αQ is the internal electrode, (6) is the internal standard solution, (2) is KCj
Ck4 is the sample inlet, and Ck4 is the sample outlet.

(2) In the ion-selective electrode of the present invention, there are few restrictions on the ion-sensitive groups that can be used, so ion-selective electrodes that respond to various ions can be produced.

■ Ion-sensitive membranes based on porous glass are not easily attacked by organic solvents, making it possible to measure ion concentrations in organic solvents. ■ Measurement sensitivity is low because there is no elution of ion-sensitive substances into the measurement solution. High ■ Since porous glass is used as the substrate for the sensitive membrane,
Can be easily processed into various shapes. (1) Since the electrical resistance of the sensitive film is extremely low, the thickness of the glass film can be approximately 1 to 5 W, resulting in high mechanical strength.

■ Compared to liquid membrane electrodes and polymer membrane electrodes, the electrode structure is extremely simple and easy to use.

■ Membrane production is very easy as sensitive groups are introduced after processing the porous glass.In addition to introducing sensitive groups, it is also easy to control the hydrophobicity of the membrane surface, making it ideal for target ions. It can be made into a sensitive film.

■ Improve specificity by immobilizing a mixture of multiple ion-sensitive substances. be able to.

Example EXAMPLES The present invention will be explained in more detail below with reference to Examples.

Example 1 A disc-shaped porous high silicate glass with a diameter of 7mm and a thickness of 1l was heated in an electric furnace at about 550°C for 2 hours to decompose and remove attached organic matter. Next, after the porous glass reached room temperature, it was placed in 5% HC7j and refluxed for 6 hours to activate the glass surface. After the activated porous glass was sufficiently vacuum-dried, the sensitive substance was immobilized by the following method.

As a sensitizer, I3 is octadecyldimethyl(3-()limethocycilyl)propyl]-antnium chloride and CM.

k(+), expressed as cge (CH30
)3Si(CH2)3CI3CM.

Two types of trimethyl(3-(trimethoxysilyl)diyl)ammonyl chloride were used, 0.5 wtl of each 50% methanol solution was added to 2 ml of toluene, and porous cells were prepared using the activation treatment described above. High silicate glass was immersed in the solution and refluxed for 4 hours. After that, wash with toluene and ethanol in that order and dry thoroughly.90Also, as a comparative example,
Bovine samethyldisilazane (hereinafter referred to as HMDS 5) o
[o% (V/V)Porous high silicate glass that had been activated was immersed in an E-dried toluene solution, and the same treatment as described above was performed to cover the surface of the porous glass with methyl groups. A glass-sensitive membrane was also fabricated.

The three types of sensitive membranes and untreated porous glass membranes obtained in this way were each fixed with parafilm at the tip of a glass tube with an inner diameter of 6M and a length of 120fl, and then the IQ
MKCl was added and an Af/AfC4 internal electrode was inserted to create a Cg'''' ion electrode.◎1O to M
Figure 4 shows the results of measuring the concentration-potential response characteristics in a C4 aqueous solution using an Af/AfC4° reference electrode. In Figure 4, (4) is trimethyl(3-(trimethoxysilyl)propyl)a:/℃ nium chloride,
In the case of electrodes with immobilized sensitizers, (6) is 0; for comparison, trioctyl methyla:
This is the case of a known anion-selective polymer membrane type electrode that maintains nium chloride at 1°C. Further, Q is the measurement result for the glass membrane subjected to HMDS treatment, and ■ is the measurement result for the untreated porous glass membrane.A response to cations can be seen in the electrode using untreated porous glass as the sensitive membrane.

This is considered to be because the 5i-OR group on the glass surface acts as a cation exchange group. It can be seen that this is suppressed by the HMDS treatment. On the other hand, trimethyl (
3-(trimethocysilyl)puryl]a: The porous glass membrane electrode immobilized with J'e nium chloride responds accurately to the logarithm of the Cj- ion concentration, and the chemical modification The effect is clear. It also shows that the response in the low concentration range is superior to that of the PVCM electrode.

Example 2 Octadecyl dimethyl (
Q
After sufficiently exchanging the counter anion of quaternary A:J72-B fixed by immersion in M NaClO4 aqueous solution for 6 hours or more, from C4- to ClO4-,
As internal liquid, KCjlo M and NaClO410
M? A C404-ion electrode was prepared in the same manner as in Example 1, except that a water-containing FA solution was used. 10 -10
Figure 5 shows the results of measuring the concentration-potential response characteristics of M in an aqueous solution of NaCJQa. ]Porous glass membrane electrode with immobilized acinium perchlorate; The results are shown in Figure 5. The porous glass membrane electrode immobilized with octadecyldimethyl ('3-()rimetoxicylyl)propylene ammonium perchlorate has a large effect on the logarithm of the ClO4- ion concentration. In addition to responding accurately, Example 1
As in the case of , it is clear that the response characteristics in the low concentration range are superior to those of PVC membrane electrodes. Trimethyl (3-()
Ammonium chloride was fixed and used to construct a flow-through electrode as shown in Figure 3. Chloride ions in a flowing liquid sample whose ionic strength was maintained at 0.1 M using sodium sulfate, which has poor selectivity for this membrane, as a supporting electrolyte: JW 1 degree is lXl0 ~
FIG. 6 shows the results of measuring the concentration-potential response characteristics when the concentration was varied up to 1X10 M. In the $6 diagram, the prisoner is lXl
0-5M MC! Indicates the potential when an aqueous solution flows at a rate of 0.5 s/min, (6), 0, ■ and ■ are 10 M, 10 M, 10 M and 10 M, respectively.
K of M Can be used as a detector.

Example 4 Octadecyl dimethyl (
A porous glass membrane electrode with immobilized ammonium perchlorate was prepared, and lX
Figure 7 shows the results of determining the concentration-potential response characteristics using methanol-substituted SCE in l0 M-1xlOMNaCJOa acetonitrile solution. (2) is the measurement result using an unmodified porous glass membrane. It is clear that the Octa membrane electrode responds accurately to the logarithm of the C404- ion concentration even in acetonitrile, and the lower limit of response is also sufficiently low.@Example 5 Fabricated using the same method as Example 2 Trimethyl (3-()
Rimetobushisilyl) pu0vir] An7nium perchlorate immobilized porous glass membrane electrode and octadecyl dimethyl (3
- () Rimetoshicilyl) P0 Building] A: Regarding the J monium perchlorate immobilized porous glass membrane electrode, (40
, - ions were used as the ions to be measured, and the selectivity coefficients for various anions were measured. The measurement method was calculated by comparing the electrode potential in a NaCjOa aqueous solution with a concentration of 10 M using a single solution method and the electrode potential measured in a sodium salt solution of each anion with the same concentration. The measurement results are shown in Table 1.

From Table 1, it can be seen that the porous lath membrane on which octadecyl dimethyl [3-(trimethocysilyl) 4379°C] nium perchlorate is immobilized has high selectivity for CjO4- ions, and SCN'' It is clear that there is little interference except for trimethyl (3-(
A porous membrane in which ammonium perchlorate is immobilized has poor selectivity for CjO4- ions. In other words, simply by exchanging the terminal alkyl chain of the modifying group from an octadecyl group to a methyl group,
It is clear that as a result of reducing the hydrophobicity of the membrane surface, the selectivity for highly hydrophilic CI ions is improved by more than 100 times. In this way, the chemically modified porosity of the present invention allows even sensitive materials having the same ion-exchange groups to have marked differences in their selectivity by changing the alkylphyl chain. 1. A major feature of the glass membrane ion-selective electrode is that it becomes possible to develop a glass membrane ion-selective electrode with specific functionality.

Trimethyl(3-(trimethoxysilyl)propyl)a:J℃The porous glass membrane electrode fixed with nium chloride has a small difference in selectivity between monovalent anions and ions, but on the other hand, the known liquid membrane Since the degree of interference by other types of anions is lower than that of a 11Cj-ion electrode, it can be used to measure the C4- concentration in blood, etc. It can also be used as a flow-through mt sensor or as a matocrograph detector.

Table 1

[Brief explanation of drawings]

FIG. 1 shows an example of a sensitive substance immobilized on a glass surface. Figures 2 and 3 are diagrams showing actual embodiments of the ion-selective electrode of the present invention. - Figure 6 is a graph of responsiveness to C4- ions in a - system, and Figure 7 is a graph of responsiveness to CIO and ions in a non-aqueous solvent system. In the figure, (1) is a modified glass membrane, (2) is an internal electrode, (3) is an internal standard solution, (4) is a glass tube, (5) is a conductive film in close contact with a modified glass membrane, (6) is the lead wire, (
7) is the lead wire coating, (8) is the plastic body, (
9) is a tubular modified glass membrane, αQ is an internal electrode, (b) is an internal standard solution, (2) is an xCj solution, (2) is a sample inlet,
α◆ is the same outlet.

Claims (1)

[Claims] (1) A chemically modified glass membrane ion-selective electrode whose sensitive membrane is porous glass on which an ion-sensitive substance is immobilized.