JPH04122850A - Reference electrode - Google Patents

Abstract

PURPOSE:To inexpensively prepare the title electrode in good yield by constituting a liquid communication part of a porous polyvinyl chloride film formed by removing a plasticizer from a mixed film of polyvinyl chloride and the plasticizer. CONSTITUTION:In a comparison electrode having an internal liquid stored therein and equipped with an internal electrode and a liquid communication part, the liquid communication pat is constituted of a porous polyvinyl chloride film formed by removing a plasticizer from a mixed film of polyvinyl chloride and the plasticizer. As polyvinyl chloride, usual polyvnyl chloride or a vinyl chloride polymer having film forming properties can be used and other monomer (e.g., vinylidene chloride) may be partially contained as a constitutional unit. The plasticizer means the plasticizer of polyvinyl chloride and various org. acid esters, for example, phthalic esters (dibutyl phthalate), adipic esters (dibutyl adipate) or sebacic ester (di-2-ethylhexyl sebacate) are pref. designated. As a solvent, a usual polar org. solvent capable of dissolving both of polyvinyl chloride and the plasticizer, for example, tetrahydrofuran is designated.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a reference electrode. More specifically, the present invention relates to a reference electrode that is used in combination with various ion-selective electrodes, and is particularly suitable for flow-through type electrodes.

(B) Prior Art Conventionally, in electrolyte analysis using various ion-selective electrodes, comparison electrodes have been used in combination as standards for potential measurement, and these are sometimes called reference electrodes, standard electrodes, etc.

These electrolyte analysis systems are typically classified into so-called stick type and flow-through type.

In stick-type analysis systems, measurements are performed with a rod-shaped ion-selective electrode with an ion-sensitive membrane at the tip immersed in the sample solution along with a rod-shaped reference electrode. A device that stores an internal liquid such as a potassium aqueous solution and is equipped with an internal electrode made of Ag/AgC1 or the like and a liquid junction made of porous ceramics, glass sleeve (ground), etc. is widely used.

On the other hand, slow-through analysis systems have become popular in recent years due to the automation of analyzers and demands for miniaturization of samples, and as reference electrodes, open liquid junction type analysis systems as shown in Figure 2 are used as reference electrodes. (In the figure, 1011 is a flow channel, 12 is a reference electrode, 13 is an ion-selective electrode, 13A is an internal electrode, 14 is
15 is the ion-sensitive membrane, 15 is the reference electrode solution, and 16 is the liquid pump), and as shown in Figure 3, the stick-shaped reference electrode is installed as it is in the flow channel, and its liquid junction is connected to the normal half. A membrane-liquid junction type constructed of a porous plastic membrane such as a permeable membrane (in the figure, 11 is a flow channel, 17 is a reference electrode, 1
Two types are widely available: 7A is an internal pole, 18 is an internal liquid, and 19 is a semipermeable membrane.

(c) Problems to be Solved by the Invention However, in the open liquid junction type reference electrode in the above-mentioned flow-through analysis system, the structure of the flow channel is complicated, and control of the sample and the reference electrode liquid for the liquid junction is complicated. Furthermore, since the reference electrode solution is used for each analysis, the reference electrode solution is consumed in a short period of time, and it is necessary to periodically add or replace the solution.

On the other hand, in a model reference electrode in a flow-through analysis system, it was difficult to install a semipermeable membrane that would serve as a liquid junction. In particular, since the flow channel is tubular and the amount of sample is relatively small, the internal solution (reference electrode solution) leaking through the liquid junction cannot be ignored, especially when the semipermeable membrane is not properly installed. However, this leakage tends to contaminate the sample and cause errors in the measured values, which ultimately leads to a decrease in the yield of the analyzer.

The present invention has been made under such circumstances, and is particularly intended to provide a reference electrode having a membrane-like liquid junction which eliminates the problem of internal liquid leakage.

(d) Means for Solving the Problems Thus, according to the present invention, in the reference electrode which stores an internal liquid and is provided with an internal electrode and a liquid junction, the liquid junction has a
A comparison electrode is provided that is made of a porous polyvinyl chloride film obtained by removing the plasticizer from a mixed film of polyvinyl chloride and a plasticizer.

In order to achieve the above-mentioned object, the present invention employs a method of constructing the liquid junction with a porous polyvinyl chloride film formed by a specific method.

The reference electrode of the present invention is made by applying an organic solvent solution containing polyvinyl chloride and a plasticizer to an open part (liquid junction part) of a container or cavity that can store an internal liquid using an appropriate support material. By drying, a mixed film made of polyvinyl chloride and a plasticizer is first stretched, and then this mixed film is
It can be obtained by dissolving and removing the plasticizer in the mixed membrane and making it porous by treating it with an organic solvent that does not substantially dissolve polyvinyl chloride but can dissolve the plasticizer.

As the above-mentioned polyvinyl chloride, ordinary polyvinyl chloride or vinyl chloride polymer having film-forming properties can be used, and other monomer components (for example, vinylidene chloride, etc.) may be partially included as a constituent unit. . On the other hand, plasticizer means a plasticizer for polyvinyl chloride, and various organic acid esters, such as phthalate esters (dibutyl phthalate,
didecyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, di-isooctyl phthalate, didecyl phthalate, etc.), adipic acid esters (dibutyl adipate, dioctyl adipate, etc.)
, sebacic acid esters (di-2-ethylhexyl sebacate, dioctyl sebacate, etc.) are suitable, and other known plasticizers can also be used. In addition, the mixing ratio of such plasticizer is suitably 5 to 70 parts with respect to 100 parts of polyvinyl chloride, and 1
0 to 30 parts is preferred.

Examples of the solvent for such a polyvinyl chloride/plasticizer-containing solution include common polar organic solvents that can dissolve both of them, such as tetrahydrofuran (THF).

The coating of the polyvinyl chloride/plasticizer-containing solution and the stretching of the mixed membrane by drying are carried out in the open area that will become the liquid junction area, as described above, and an appropriate support material (core) is placed on the outside of this open area. etc.) and closing the container, injecting a predetermined amount of the polyvinyl chloride/plasticizer-containing solution and drying with air or heat. Note that the thickness of the mixed membrane is not particularly limited, but is usually 0.05 to 1.0.
Approximately μm is appropriate.

The organic solvent used to remove the plasticizer from the mixed membrane stretched in this way, that is, polyvinyl chloride, does not substantially dissolve, but the organic solvent that can dissolve the plasticizer is a hydrophilic organic solvent. Solvents are suitable, including lower alcohols such as methanol, ethanol, and ituburobanol. The treatment with such an organic solvent can be carried out by washing the upper and lower surfaces of the stretched portion of the mixed membrane with the organic solvent for a certain period of time or by immersing it in the organic solvent for a certain period of time. Through such treatment, a liquid junction consisting of the porous polyvinyl chloride membrane of the present invention is constructed, and then an appropriate internal liquid such as potassium chloride solution is injected and Ag/Ag
By arranging a suitable internal pole such as C1, a comparison electrode of the present invention can be obtained.

(e) Since the working liquid junction is made of a porous polyvinyl chloride membrane formed on the spot by a plasticizer removal method, it can be easily stretched and the membrane-like liquid can be prevented from leaking internal liquid. The connecting portion can be easily constructed.

(F) EXAMPLES The present invention will be explained in detail below with reference to Examples, but the present invention is not limited thereby.

First, 1 g of commercially available polyvinyl chloride powder and 0.29 grammes of di-2-ethylhexyl sebacate as a plasticizer were weighed and dissolved in tetrahydrofuran 1011Q.

Store this mixed solution in a brown glass bottle in a cool, dark place.

Next, as shown in FIG. 1(A), a reference electrode body made of PVC is equipped with a cavity 3 having a diameter of 4xx, a tapered opening 4 (2JIIIφ), and a flow channel (1!throughφ). 2
prepared. A cylindrical core 6 (made of glass) was inserted into the flow channel 5 of the electrode body 2 so that the opening 4 was closed (see FIG. 1(B)). In this state,
The cavity 3: It is shaped like a container.

Next, 50 μQ of the previously prepared THF solution of polyvinyl chloride/plasticizer is injected into the cavity 3 and left to stand, so that the THF solvent evaporates, and after 24 hours, the polyvinyl chloride/plasticizer solution is injected. A transparent thin film 7 (center thickness approximately 100 μm) made of a plasticizer mixture was formed in the opening 4 (see FIG. 1(c)).

Next, after removing the core 6, the cavity 3 and the flow channel 5 are removed.
By enclosing ethanol inside and leaving it for about 60 minutes, the plasticizer component (2-ethylhexyl separate) in the thin film 7 was dissolved and removed, and a porous polyvinyl chloride film 7° was obtained.

Next, a saturated potassium chloride aqueous solution 8 was injected into the cavity 3, and an Ag/AgCl electrode 9 was inserted as an internal electrode, thereby obtaining a comparative electrode 1 of the present invention as shown in FIG. 1(D). Ta.

This comparative electrode 1 functioned as a comparative electrode having a good and stable reference potential in a flow-through system as shown in FIG. Since the porous polyvinyl chloride film 7° was formed on the spot at the liquid junction, there was no dead space and leakage of the internal liquid was prevented as much as possible.

(G) Effects of the Invention The reference electrode of the present invention has a membrane-like liquid junction that prevents unnecessary leakage of internal liquid, and this liquid junction can be easily formed. Therefore, it can be manufactured at low cost and with high yield, and is extremely useful in this field.

[Brief explanation of drawings]

FIG. 1 is a structural explanatory diagram showing the manufacturing process of a comparison electrode of the present invention, and FIGS. 2 and 3 are structural explanatory diagrams showing an open liquid junction type comparison electrode and a membrane liquid junction type comparison electrode, respectively. DESCRIPTION OF SYMBOLS 1... Comparison electrode, 2... Comparative electrode body, 3... Cavity, 4... Opening, 5
...Flow channel, 6... Core, 7...
... Thin film, 7° ... Porous polyvinyl chloride membrane, 8 ... Saturated potassium chloride solution, 9 ...
...Ag/AgC1 electrode. No.8 Yasuto No. Sonodaien

Claims (1)

[Claims] 1. In a reference electrode that stores an internal liquid and includes an internal electrode and a liquid junction, the liquid junction removes the plasticizer from a mixed film of polyvinyl chloride and a plasticizer. A reference electrode composed of a porous polyvinyl chloride membrane.