JPH01244354A - Uranyl-ion selective electrode characterized by long life - Google Patents

Abstract

PURPOSE:To obtain an uranyl-ion selective electrode characterized by excellent reproducibility, accuracy and durability and a long life, by providing both potassium chloride and uranyl ions together as internal liquid in contact with a sensitive film. CONSTITUTION:An intended uranyl-ion selective electrode is of an ion exchange type. Namely, an independent internal reference electrode having a junction is provided in the inside. Uranyl-ion inner liquid having a specified concentration is filled between said electrode and an outer tube. Solution under test and the inner liquid are in contact with an uranyl-ion exchange liquid film that is a part of the outer tube in-between. On the inner liquid composition for the inner reference electrode and the inner liquid composition for the uranyl ion electrode, i.e., potassium chloride and uranyl ions, are made to coexist in this structure. In this way, the uranyl-ion selective electrode characterized by excellent concentration response, excellent reproducibility, accuracy and durability and a long life is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present description relates to long-life uranyl ion-selective electrodes. More specifically, uranyl fist ion exchange membranes are used.

The present invention relates to a long-life uranyl ion-selective electrode with excellent concentration response, excellent reproducibility, accuracy, and durability.

<Prior Art> With the recent development of the atomic crab industry, practical research is underway on electrodes for uranyl ion analysis, which are indispensable to the atomic crab industry. Various reports have already been made regarding ion exchange membrane type uranyl ion selective electrodes in which a reference electrode is placed inside and an internal solution of uranyl ions at a certain concentration is filled between this and the outer cylinder.

For example, Dietrich (W, C, Dietrich)
is di-2-ethylhexyl phosphate (02EHP
) and polyvinyl chloride (
reported that pvc) membranes are sensitive to uranyl ions (
Technical Progress Report
No, Yl1740, Y-12Develop
ment Division, Aug, -0ct
.

(1971)), while Manning et al. (D, L, M
Anning et al.) investigated the properties of PvC-based reaction membranes of acidic phosphate ester-uranyl ion complexes using acidic and neutral phosphonates or phosphates as diluents, and found several types of membranes with good sensitivity. However, the slope of the potential difference correlated with the concentration response with respect to the common logarithmic concentration (hereinafter simply referred to as the potential difference gradient) is at most 26 m.
V/decade, it was smaller than the Nernst equation theoretical potential gradient for divalent ions (hereinafter simply referred to as the Nernst gradient) (Anal, Cherl,...
Vol, 48. No, 8. pp, 111B-
1119 (1974)), and furthermore, Goldbarb et al.
(I.

Goldberg et al.) used D2EHP, tributyl phosphate (TBP), and any of a variety of phosphonates as diluents, and used acidic, neutral phosphates, phosphites, or acidic phosphonates with uranyl ions. We investigated the properties of PvC-based sensitive membranes in complexes with phosphite esters, and obtained a potential difference gradient close to the Nernst gradient using a phosphite-based sensitive membrane (Anal, Cher.
a,, Vol, 52. pp, 2105-210
8 (1980)), Shiga et al. used a sensitive membrane treated with a diluent that has excellent compatibility with the ion exchanger and a solvent that has affinity with the membrane-forming substrate. A selective electrode was obtained (patent application 1981-
150559), however, these documents do not report on the lifespan of the electrodes, except in one case, in which the lifespan is two weeks, which is extremely insufficient.

<Problems to be solved by the invention> In general, the longer the lifespan of an electrode, the more practical it is as a sensor.However, in the above reports, there is almost no report on the lifespan of the electrode, and even if the electrode has reached the level of being an industrial sensor. However, as shown in the comparative example below, in the research conducted by the present inventors, the lifespan of these products could not be said to be sufficient.

As a result of intensive studies in view of the current situation, the present inventor has completed the present invention by realizing an industrially usable uranyl ion electrode that has a lifespan of 5 months or more.

Means for Solving Problems> The present invention provides an ion-exchange liquid membrane type electrode in which the membrane-forming substrate is made of one or two types of uranyl ion complexes of neutral phosphate esters or neutral phosphite esters. An ion exchanger comprising the above, a diluent having excellent compatibility with the ion exchanger,
In a uranyl Φ ion electrode using a sensitive membrane treated with three types of reagents: and a solvent having affinity with the membrane-forming substrate and a second type electrode as an internal reference electrode, as an internal liquid in contact with the sensitive membrane, This invention relates to a uranyl ion selective electrode characterized in that potassium chloride coexists with uranyl ions.

The present invention will be explained in detail below.

The uranyl ion selective electrode according to the present invention is of the ion exchange liquid membrane type. That is, an independent internal reference electrode equipped with a junction is placed inside, and an internal solution containing uranyl ions of a certain concentration is filled between this electrode and the outer tube, and the test solution and the inner solution are uranyl ions that are part of the outer tube. Either the internal reference electrode is in contact with an exchange liquid membrane across it, or the internal reference electrode is only an electrode element, and the internal liquid composition for the internal reference electrode and the internal liquid composition for the uranyl ion electrode, that is, uranyl ion. It is a structure that allows both to coexist.

In the present invention, as the internal reference electrode, conventionally used general electrodes can be used, such as a silver-silver chloride electrode, a calomel electrode, or a mercurous mercury sulfate electrode. There is no particular restriction on the structure, and it may be a single φ junction type or a double junction type. It may also be immersed in an internal liquid as an electrode.

The film-forming base material used in the present invention is preferably a material capable of forming an ion-exchange liquid film, such as polyvinyl acetate, silicone rubber, cellulose acetate, polyvinyl chloride, or epoxy resin. Among these, polyvinyl chloride is particularly preferred.

As the complexing agent for forming the ion exchanger, a neutral phosphoric acid ester or a neutral phosphorous acid ester is used. These esters each have alcohol residues with 2 to 2 carbon atoms.
0 alkyl groups or halogenated alkyl groups are preferably used. Examples of alkyl groups having 2 to 20 carbon atoms or halogenated alkyl groups include ethyl, propyl,
Butyl, hexyl, octyl, dodecyl or their halogen substitutes. Of course, the three alcohol residues do not have to be the same.

Specifically, tri-n-butyl phosphite, trioctyl phosphate, and trichloropropyl phosphate.

Tri-n-chloroethyl phosphate, trichlorobutyl phosphate, trichlorooctyl phosphate, dibutyldecyl phosphite, diethyldecyl phosphite.

Examples include dibutyldecyl phosphate and diethyldecyl phosphate. These can be used alone or in combination.

Next, as a diluent having excellent compatibility with the above-mentioned ion exchanger, a neutral phosphoric acid ester can be suitably used. These esters each have alcohol residues with 2 to 2 carbon atoms.
Examples of the alkyl group having 2 to 20 carbon atoms, preferably 0 alkyl group, include ethyl, propyl, butyl, hexyl,
Examples include octyl, dodecyl, etc. Among them, carbon number 3
8 alkyl groups are preferred.

Specifically, triethyl phosphate, tripropyl phosphate,
Trihexyl phosphate, trioctyl phosphate, tridodecyl phosphate, etc., among which tributyl phosphate is preferably used.

In addition, hair dyes and the like are used as solvents that have affinity with the film-forming substrate (compatible solvents), such as phthalate esters,
Examples include adipic acid ester, sebacic acid ester, and other glycol derivatives. Among them, phthalic acid esters, adipic acid esters and sepacic acid esters are preferred. In these esters, each alcohol residue is preferably an alkyl group having 2 to 20 carbon atoms.
Examples of the alkyl group having 2 to 20 carbon atoms include ethyl, propyl, butyl, heptyl, and dodecyl. Among these, an alkyl group having 3 to 8 carbon atoms is preferred.

Specifically, dioctyl phthalate (DOP), dioctyl adipate (DOA), dioctyl sebacate (DO
3) etc.

The complexing agent is used in a ratio of 2 to 3 moles, particularly preferably 2.0 to 2.5 moles, per mole of uranyl nitrate hexahydrate for preparing the uranyl ion internal solution described below. The mixing ratio of diluent and compatible solvent is 3/1 to 1 by weight.
/3 is particularly preferably 2/1 to 1/2, and the ion exchanger made from the complexing agent and uranyl nitrate is preferably 1/7 to 1/20 in weight ratio to the mixture of the diluent and compatible solvent. are mixed at a ratio of 178 to 1/15, and the mixture of these ion exchangers, diluents, and affinity solvents has a film forming base material of 20% to 50% by weight, preferably 25% to 35% by weight of the total.
The mixture is used as a film-forming base material by weight percentage.

In the present invention, the membrane-forming base material is an ion exchanger made of one or more uranyl ion complexes of a neutral phosphate ester or a neutral phosphite, and an ion exchanger having excellent compatibility with the ion exchanger. Any method may be used to obtain a sensitive film treated with a diluent and a solvent that has an affinity for the film-forming base material6. There is also a method of thermoforming, but for boat fishing, after dissolving the film forming base material in a volatile good solvent such as tetrahydrofuran or cyclohexanone, the above-mentioned ion exchanger, diluent, and compatible solvent are used. It can be obtained by evaporating the good solvent after mixing or adding them one after another to make a homogeneous solution.

The thickness of the film is suitably adjusted to 0.1 ml to 0.8 mm, and particularly preferably 0.2 to 0.6 mm.

uranyl ion internal solution in contact with the ion exchange membrane;
That is, the internal liquid serving as the indicator electrode dissolves uranyl ions and potassium chloride. There are no particular restrictions on the concentration.

The uranyl ion concentration is preferably close to the concentration of the liquid to be measured, and the potassium chloride concentration is preferably a concentration commonly used in comparison electrodes with partition walls.

<Example> (Experimental Method) Common experimental methods from sensitive membrane prototype production to potential difference measurement are described below. In the present invention, experiments were conducted based on these unless otherwise specified.

(t) Preparation of PVC-ion exchanger sensitive membrane 1) Preparation of ion exchanger Add phosphate ester (or phosphite ester) to 1.00 g of uranyl nitrate hexahydrate in a molar ratio of 2.
Add. This is thoroughly stirred and shaken until the solid phase of uranyl nitrate disappears to form a complex. If an aqueous phase forms in the lower layer at this time, use a centrifuge to completely separate the aqueous and oil phases, and then remove the aqueous phase using a syringe, etc., leaving behind a viscous yellow liquid (oil phase). is a complex of phosphate ester (or phosphite ester) and uranyl nitrate, and to this is added 100+ag of anhydrous sodium sulfate twice, centrifuging each time to remove water in the complex. This ion exchanger (complex) is stored in a dry, capped test tube.

2) Preparation of sensitive membrane Weigh out 45 mg of the ion exchanger and 400 mg of the mixed solvent into a dry 50-1001 beaker so that the weight ratio of the ion exchanger and the mixed solvent is about 1:9, and stir well. The ratio of diluent and compatible solvent in the mixed solution is 1:1
And so.

However, there are cases where only one of the diluent and the compatible solvent is used. In that case, of course, add 400 mg of the solvent.

To this solution, a solution 61 in which 1.75 g of hard PVC (manufactured by Sumitomo Chemical 5X-DH viscosity average degree of polymerization 2820) was dissolved in 8'hl of tetrahydrofuran (THF) was added and stirred well. This solution is 30m in diameter.
Pour into a dry petri dish, cover with 2 to 3 pieces of filter paper, and leave to stand in a fume hood horizontally to gradually evaporate the solvent, HF, and dry. Drying time shall be at least 36 hours.

(2) Assembling the electrode The dried PVC sensitive membrane is cut out onto a disk with a diameter of 12+ am using a cork polar cutter, etc., and adhered to one end of an intestinal PvC tube with an external diameter of 12 mm and a length of 30 to 40 mm. The adhesive used was one in which 7 g of PVC was dissolved in 8 h+ of THF. After the adhesive part has sufficiently dried, before using it as an electrode film, perform so-called conditioning by soaking both sides of the PvC sensitive film in 10'H uranyl standard concentration solution for at least 24 hours, preferably for at least 72 hours. ,
Also, when removing the electrode membrane and storing it, soak it in this standard solution.To assemble the electrode, attach the above-mentioned PvC tube with the membrane glued to the tip of the silver-silver chloride reference electrode, and fix it with sealing tape so that it does not come off. . Note that a 10-tM uranyl nitrate solution (pH-3.0) is filled in advance as an internal solution between the electrode film and the reference electrode.

Therefore, the structure of this electrode (indicator electrode) can be written as follows.

Ag/AgC:l, KOI I UO2 (No
:l) 2. 10-”M (pH=3
) l Membrane 1 (3) Preparation of standard concentration uranyl nitrate aqueous solution 10 →, 10-2 adjusted using IN HNO:1 or IN KOH solution so that the pH was 3.0 before potential difference measurement
A uranyl e ion standard solution of 10-1 and 10=H was prepared and used.

(4) Potential difference measurement method A battery was assembled using the above indicator electrode and the same electrode as its internal reference electrode as an external reference electrode, and the electromotive force (potential difference) was measured at 25±2°C using a pH/mV system F-8AT model manufactured by Ageba. It was measured with The beaker containing the sample solution was slowly stirred with a magnetic stirrer. A heat insulating mat was placed between the beaker and stirrer to prevent the temperature of the liquid from rising. 1
The point at which the potential change in 0 minutes was 1 mV or less was read as the confirmed potential at that concentration.

(5) Lifetime measurement method The indicator electrode, which has been measured using the potentiometric method described above, is lifted from the sample solution and then immersed in a storage solution.The storage solution is the same 10-tM uranyl standard concentration solution used for conditioning. It is. After the specified time (about 10 days) has passed (
Measure the potential difference using method 4). When this storage and measurement is repeated, the potential difference gradient hardly changes over time, but the indicated potential begins to oscillate over time. If the amplitude exceeds 2 sV two or more times in a row, the first measurement point is determined to be the end point of the electrode life.

Comparative Example 1 The ion exchanger of the above experimental method (1) 1) was prepared using twice the molar amount (based on uranyl ions) of DBP or D2EHP, and the sensitive membrane preparation of 2) was carried out using only TBP in the mixed solvent. The life of the electrodes used was about 15 days.

Comparative Example 1 uses dibutyl phosphate (DBP) or D2 as a representative example of the experiments of Deitrich et al. and Manning et al.
TB using EHP-uranyl ion complex as an ion exchanger
This is a life test of a PvC-based sensitive film using P as a diluent. This result indicates that the lifetime of their prototype electrode is not sufficient for industrial use.

Comparative Example 2 Tri-n-butyl phosphite complexing agent, diluent T
Sensitive films were prepared using BP and the affinity solvent was DOA or DOS, and their lifetimes were measured. As a result, a lifespan of about 30 days was obtained.

Comparative Example 2 is a PVC base material using tri-n-butyluranyl phosphite ion complex as an ion exchanger, TBP as a diluent, and DOA or DOS as an affinity solvent, as a representative example of Shiga et al.'s experiment. This is a life test of a sensitive membrane.

This result shows that although the life of their prototype electrode is better than Comparative Example 1, it is still not sufficient for industrial use.

Example 1 In Comparative Example 2, (2) During electrode assembly, a 10-2 uranyl nitrate solution containing KCI of pH-3 and 3.33H was used as an internal solution between the electrode membrane and the reference electrode. A solution prepared as above was used.

As a result, a lifespan of over 150 days was obtained.

Example 2 In Example 1, a calomel electrode was used as the internal comparison electrode. In this case as well, the lifespan exceeded 150 days.

Example 3 In Example 1, a mercurous sulfate electrode was used as the internal comparison electrode. In this case as well, the lifespan exceeded 150 days.

Example 4 In Comparative Example 2, the outer cylinder of the silver-silver chloride internal electrode was removed, leaving only the electrode element, and the life of the indicator electrode was measured by immersing it in the cylinder containing the ion exchange membrane and internal solution of Example 1. . As a result, we achieved a lifespan of over 150 days.

Comparative Example 3 A sensitive membrane was prepared using tri(chloropropyl) phosphate as a complexing agent, TBP as a diluent, and DOPt or DOA as an affinity solvent, and a life test was conducted. The lifespan of all of them was less than 30 days.

Example 5 In Comparative Example 3, four types of uranyl ion electrodes with the same improvements as in Examples 1, 2, 3, and 4 were fabricated, and the lifespan of each was measured.

As a result, all of them showed a lifespan of 150 days or more.

Example 6 Trioctyl phosphate as complexing agent, TBP as diluent, D
A sensitive membrane using OA as an affinity solvent was prepared, and Example 1.2,
Four types of electrodes were assembled using the method shown in 3.4, and a life test was conducted on each. Their lifespan is 1
It's been over 50 days.

Example 7 Dibutyldecyl phosphate as a complexing agent, TBP as a diluent,
An electrode life test was conducted using the same assembly method as in Example 4 for a sensitive film using DOP, DOA, or DOS as an affinity solvent.

All showed a lifespan of 150 days or more.

<Effects of the Invention> The present invention provides a uranyl ion selective electrode with excellent uranyl Φ ion selectivity and concentration response, and a long life. It can be said that it provides a practical electrode in the atomic crab industry, especially as an electrode for uranyl ion analysis.

Claims (1)

[Claims] In the ion-exchange liquid membrane type electrode, the membrane-forming substrate is a neutral phosphate ester or a neutral phosphite uranyl ester.
A sensitive membrane treated with three types of reagents: an ion exchanger made of one or more types of ion complexes, a diluent with excellent compatibility with the ion exchanger, and a solvent with affinity with the membrane forming substrate. A long-life uranyl ion selective electrode characterized in that potassium chloride coexists with uranyl ions as an internal liquid in contact with a sensitive membrane in a uranyl ion electrode using a second type electrode as an internal reference electrode.