JPH063426B2 - Long-lived uranyl ion-selective electrode - Google Patents

Description

TECHNICAL FIELD The present invention relates to a long-lived uranyl ion-selective electrode. More specifically, it has a uranyl ion exchange membrane,
The present invention relates to a long-life uranyl ion-selective electrode having excellent concentration responsiveness, reproducibility, accuracy and durability.

<Prior Art> Along with the recent development of the nuclear industry, practical research of an electrode for uranyl ion analysis, which is indispensable for the nuclear industry, is underway. Various reports have already been made on the ion-exchange liquid membrane type uranyl ion-selective electrode in which the reference electrode is placed inside and the inner tube of the reference electrode is filled with a constant concentration of uranyl ion internal solution.

For example, WC Dietrich reported that a polyvinyl chloride (PVC) film containing a complex of di-2-ethylhexyl phosphate (D2EHP) and uranyl ion was sensitive to uranyl ion (Technical Progress Report No.
Y1174D, Y-12 Development Division, Aug.-Oct. (197
1)). On the other hand, DL Manning et al. (PV) of acidic phosphoric acid ester-uranyl ion complex using acidic neutral phosphonic acid ester or phosphoric acid ester as a diluent.
The properties of the C-based reaction film were investigated, and several types of films with good sensitivities were obtained. 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) was at most. It was smaller than the theoretical potential difference gradient (hereinafter simply referred to as Nernst gradient) for doubly charged ions of Nernst equation at 26 mV / decade (Anal. Chem., Vol. 46, No. 8, pp. 1116-1119 (197).
Four)). In addition, I. Goldberg et al.
PVC base material of EHP, tributyl phosphate (TBP), and various phosphonates as diluents, and acidic, neutral phosphates, phosphites or complexes of acidic phonates with uranyl ions The properties of the sensitive membrane were investigated, and a potential difference gradient close to the Nernst gradient was obtained by the phosphite-based sensitive membrane (Anal. Chem., Vol. 52, pp. 21.
05-2108 (1980)]. Shiga et al. Obtained a uranyl ion-selective electrode with a large potential difference gradient by using a sensitive membrane treated with a diluent having excellent compatibility with an ion exchanger and a solvent having an affinity for a membrane-forming substrate. (Japanese Patent Application Sho 61-15055
No. 9 bulletin). However, none of these documents reports on the life of the electrode. In that example, the life span is 2 weeks, which is far from sufficient.

<Problems to be Solved by the Invention> Generally, the longer the life of the electrode, the higher the practicality as a sensor. However, there is almost no report on the life of the electrode in the above report, and it is doubtful whether or not it has reached the level as an industrial sensor. As shown in the comparative example described later, these lives were not sufficient in the study by the present inventors.

The present inventor has conducted intensive studies in view of the above circumstances, and as a result, has realized an industrially usable uranyl ion electrode having a life of 5 months or more, and completed the present invention.

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

Hereinafter, the present invention will be specifically described.

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 with a junction is placed inside, and a constant concentration of uranyl ion internal solution is filled between this and the outer tube, and the test solution and the inner solution are the uranyl ion which is a part of the outer tube. Either they are in contact with each other through the exchange liquid membrane, or the internal reference electrode is the electrode element only, and the internal liquid composition for the internal reference electrode is potassium chloride solution and the internal liquid for the uranyl ion electrode. It has a composition, that is, a structure in which uranyl ions coexist.

In the present invention, as the internal reference electrode, a general second type electrode which has been conventionally used is used. For example, a silver / silver chloride electrode, a calomel electrode, or a mercury mercuric sulfate electrode can be used. The structure is not particularly limited and may be a single junction type or a double junction type. Alternatively, the partition wall between the internal reference electrode and the ion exchange membrane may be removed, and the electrode element may be immersed in the internal liquid as the internal reference electrode.

The membrane-forming substrate used in the present invention is capable of forming an ion exchange liquid membrane. For example, polyvinyl acetate, silicone rubber, cellulose acetate, polyvinyl chloride, epoxy resin and the like are preferably used. Of these, polyvinyl chloride is particularly preferable.

Neutral phosphoric acid ester or neutral phosphorous acid ester is used as a complexing agent forming an ion exchanger. These esters have alcohol residues of 2 to 2 carbon atoms, respectively.
An alkyl group of 0 or a halogenated alkyl group is preferably used. Examples of the alkyl group having 2 to 20 carbon atoms or the halogenated alkyl group include ethyl, propyl,
There are butyl, hexyl, octyl, dodecyl or their halogen substitutions. Of course, the three alcohol residues need not be the same.

Specifically, tri-n-butyl phosphite, trioctyl phosphate, trichloropropyl phosphate, tri-n-phosphate.
Examples thereof include chloroethyl, trichlorobutyl phosphate, trichlorooctyl phosphate, dibutyl decyl phosphite, diethyl decyl phosphite, dibutyl decyl phosphate, and diethyl decyl phosphate. These can be used alone or in combination.

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

Specifically, triethyl phosphate, tripropyl phosphate,
Examples thereof include trihexyl phosphate, trioctyl phosphate, tridodecyl phosphate, and tributyl phosphate is preferably used.

Further, a plasticizer or the like is used as a solvent having an affinity with the film-forming substrate (affinity solvent).
Examples thereof include adipate ester, sebacate ester, and other glycol derivatives. Among them, phthalic acid ester, adipic acid ester and sebacic acid ester are preferable. The alcohol residue of each of these esters 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 preferable.

Specifically, dioctyl phthalate (DOP), dioctyl adipate (DOA), dioctyl sebacate (DO
S) and the like.

The complexing agent is used in a ratio of 2 mol to 3 mol, particularly preferably 2.0 mol to 2.5 mol, per 1 mol of uranyl nitrate hexahydrate for adjusting the internal liquid of uranyl ion described later. The mixing ratio of the diluent and the affinity solvent is 3/1 to 1/3 by weight, particularly preferably 2/1 to 1/2, and the ion exchanger made from the complexing agent and uranyl nitrate is a diluent. 1/7 to 1/20, preferably 1/8 to 1/15, and a mixture of these ion exchangers, diluents, and affinity solvents in a weight ratio with the mixture of Is 20 wt% to 50 wt% of the total, preferably 25
Used as a film-forming substrate by mixing so as to be from 35% by weight to 35% by weight.

In the present invention, the film-forming substrate is an ion exchanger comprising one or more neutral phosphoric acid ester or uranyl ion complex of neutral phosphorous acid ester, and excellent compatibility with the ion exchanger. Any method may be used as a method for obtaining a sensitive film by treating with a diluent and a solvent having an affinity for the film-forming substrate. For example, there is a method of directly mixing a film-forming substrate with a complex, a diluent, an affinity solvent, etc. and then thermoforming, but in general, a solvent having good dissolving power such as tetrahydrofuran or cyclohexanone is a good volatile solvent. It can be obtained by dissolving the membrane-forming substrate, mixing it with the above-mentioned ion exchanger, diluent, and affinity solvent, or sequentially adding it to obtain a uniform solution, and then evaporating the good solvent.

The thickness of the film is suitably 0.1 mm to 0.8 mm, particularly preferably 0.
Adjust so that it is 2 mm to 0.6 mm.

Uranyl ion internal liquid in contact with the ion exchange membrane,
That is, the internal liquid as the indicator electrode dissolves uranyl ions and potassium chloride. There is no particular limitation on the concentration. It is desirable that the concentration of uranyl ions be close to the concentration of the liquid to be measured, and the concentration of potassium chloride is preferably the concentration usually used for a reference electrode having a partition wall.

<Example> (Experimental method) A common experimental method from trial production of a sensitive film to measurement of a potential difference will be described below. In the present invention, unless otherwise specified, experiments were conducted based on these.

(1) Preparation of PVC-ion exchanger sensitive membrane 1) Preparation of ion exchanger Add phosphoric acid ester (or phosphorous acid ester) to 1.00 g of uranyl nitrate hexahydrate in a molar ratio of 2. . This is well stirred and shaken until the solid phase of uranyl nitrate disappears to form a complex. At this time, if an aqueous phase is generated in the lower layer, the aqueous phase and the oil phase are completely separated by a centrifuge, and then the aqueous phase is removed using a syringe or the like. The remaining viscous yellow liquid (oil phase) is a complex of phosphoric acid ester (or phosphorous acid ester) and uranyl nitrate.
Add 0 mg of anhydrous sodium sulfate twice and centrifuge each time to remove water in the complex. The ion exchanger (complex) is stored in a dry test tube with a cap.

2) Preparation of Sensitive Membrane Drying 45 mg of ion exchanger and 400 mg of mixed solvent so that the weight ratio of ion exchanger and mixed solvent is about 1: 9.
Weigh in a 00 ml beaker and stir well. The ratio of diluent to affinity solvent in the mixed solution was 1: 1. However, in some cases only one of diluent or affinity solvent is used. In that case, of course, add 400 mg of the solvent. Hard PVC (SX-DH viscosity average degree of polymerization 2620 manufactured by Sumitomo Chemical) was added to this solution beforehand.
Add 6 ml of a solution prepared by dissolving 1.75 g in 60 ml of tetrahydrofuran (THF) and stir well. The solution is poured into a dry petri dish having a diameter of about 30 mm, a paper is covered with a few plates, and the solution is allowed to stand in the draft while keeping it horizontal to gradually evaporate THF as a solvent to dry. The drying time should be 36 hours or longer.

(2) Assembling the electrode Cut the dried PVC sensitive film into a disk with a diameter of 12 mm using a cork borer, cutter, etc.
Glue to one end of a 30-40mm PVC tube. P for adhesive
A solution prepared by dissolving 7 g of VC in 60 ml of THF was used. After the adhered part has dried sufficiently, before applying it to the electrode film, soak it for 24 hours or more, preferably 72 hours or more so that both sides of the PVC sensitive film are in contact with 10 ^-2 M standard uranyl concentration solution. To do. Also, when removing and storing the electrode membrane, soak it in this standard solution. To assemble the electrode, attach the above-mentioned PVC tube with a film attached to the end of the silver-silver chloride reference electrode and secure it with a sealing tape so that it will not come off. An internal solution of 10 ⁻² M uranyl nitrate solution (pH = 3.0) was previously filled between the electrode film and the reference electrode. Therefore, the structure of this electrode (indicator electrode) can be written as follows.

(3) Preparation of Uranyl Nitrate Aqueous Solution at Standard Concentration 1N HNO ₃ or 1N KOH to adjust the pH to 3.0 before measuring the potential difference.
Solution-conditioned 10 ^-1 , 10 ^-2 , 10 ^-3 , 10 ^-4 M uranyl ion standards were prepared and used.

(4) Potentiometric measurement method A battery was assembled using the above-mentioned indicator electrode and the same internal reference electrode as the external reference electrode, and the electromotive force (potential difference) was 25 ± 2 ° C using a Horiba pH / mV meter F-8AT type. It was measured at.
The sample solution was slowly stirred with a beaker or a magnetic stirrer. A heat insulating mat was sandwiched between the beaker and the stirrer to prevent the liquid temperature from rising. The point at which the potential change within 10 minutes became 1 mV or less was read as the definitive potential at that concentration.

(5) Life measurement method The indicator electrode, which has been measured by the above-mentioned potentiometric measurement method, is pulled up from the sample solution and then immersed in a preservation solution. The stock solution is the standard 10 ^-2 M uranyl standard solution used for conditioning. After the lapse of a predetermined time (about 10 days), measure the potential difference by the method of (4). This storage and measurement are repeated. Although the potential difference gradient hardly changes with time, the indicated potential starts oscillating with time. The amplitude is 2 mV or more continuously 2 mV
When the value exceeds the limit, the first measurement time point is judged as the end point of the electrode life.

Comparative Example 1 An ion exchanger according to the above experimental methods (1) and (1) was prepared by using a double molar amount (versus uranyl ion) of DBP or D2EHP, and preparation of a sensitive membrane of TBP alone in a mixed solvent 2). The life of the electrode used for was about 15 days. The internal solution used at this time was a 10 ^-2 M uranyl nitrate solution (pH = 3).

This comparative example 1 is dibutyl phosphate (DBP) or D2E, which is a representative example of experiments such as Dietrich et al. And Manning.
HP-Uranyl ion complex as ion exchanger TBP
It is a life test of the sensitive film of the PVC base material which uses as a diluent.
This result indicates that the lifetime of their prototype electrodes is not sufficient for industrial use.

Comparative Example 2 The diluent containing T-n-butyl phosphite as a complexing agent was T.
In BP, a sensitive film in which the affinity solvent was DOA or DOS was prepared and the lifetime was measured. As a result, a life of about 30 days was obtained. The internal solution at this time was 10 ^-2 M uranyl nitrate solution (pH =
3) was used.

This comparative example 2 is a representative example of the experiment by Shiga et al., Which is a PVC group using tri-n-butyl-uranyl phosphite ion complex as an ion exchanger, TBP as a diluent, and DOA or DOS as an affinity solvent. It is a life test of the sensitive film of the material.
The results show that their prototype electrodes have a longer life than Comparative Example 1, but are still not sufficient for industrial use.

Example 1 In Comparative Example 2, (2) when assembling the electrode, 10 ⁻² M uranyl nitrate solution was used as an internal solution between the electrode membrane and the reference electrode so that pH = 3 and 3.33 N KCl was included. The prepared solution was used. As a result, it has a life span of over 150 days.

Example 2 In Example 1, a calomel electrode was used as the internal reference electrode. In this case as well, the life was over 150 days.

Example 3 In Example 1, a mercury mercuric sulfate electrode was used as an internal reference electrode. In this case as well, the life was over 150 days.

Example 4 In Comparative Example 2, the outer cylinder of the silver-silver chloride internal electrode was removed, and only the electrode element was used. The life of the indicator electrode was measured by immersing it in the cylinder containing the ion exchange membrane and the internal liquid of Example 1. . As a result, I got a life of 150 days or more.

Comparative Example 3 A sensitive film was prepared using tri (chloropropyl) phosphate as a complexing agent, TBP as a diluent, and DOP or DOA as an affinity solvent, and a life test was conducted. Their lifespan was less than 30 days.

The internal solution used at this time was a 10 ^-2 M uranyl nitrate solution (pH = 3).

Example 5 In Comparative Example 3, four uranyl ion electrodes having the same improvements as those in Examples 1, 2, 3, and 4 were prototyped, and the life of each was measured. As a result, all of them showed a lifespan of 150 days or more.

Example 6 Trioctyl phosphate as a complexing agent, TBP as a diluent, D
A sensitive film was prepared using OA as an affinity solvent, and
Four types of electrodes were assembled by the methods shown in Nos. 3 and 4, and a life test was performed for each. The service life is 15
Over 0 days.

Example 7 Dibutyldecyl phosphate as a complexing agent, TBP as a diluent,
An electrode life test was performed on a sensitive film using DOP, DOA or DOS as an affinity solvent by the same assembly method as in Example 4. All showed a lifespan of 150 days or more.

<Effects of the Invention> The present invention provides a uranyl ion-selective electrode having excellent uranyl ion selectivity and concentration response and having a long life. This electrode has good reproducibility, accuracy, and durability, and can be said to provide a practical electrode in the nuclear industry as an electrode for uranyl ion analysis.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichiro Shigeoka 5-1 Anezaki Kaigan, Ichihara City, Chiba Prefecture Sumitomo Chemical Co., Ltd. (72) Inventor Takao Akiyama 4-33 Muramatsu, Tokai Village, Naka-gun, Ibaraki Prefecture Power Reactor・ In the Nuclear Fuel Development Corporation Tokai Works (72) Inventor Yukio Wada 4-33 Muramatsu, Tokai-mura, Naka-gun, Ibaraki Prefecture In-house Power Generation Reactor and Nuclear Fuel Development Corporation Tokai Works (72) Inventor Yasuo Suzuki, Tokai-mura, Naka-gun, Ibaraki Prefecture 4-33 Muramatsu Power Reactor / Nuclear Fuel Development Corporation Tokai Works (56) References JP 63-5256 (JP, A)

Claims (1)

[Claims] 1. An ion-exchange liquid membrane electrode, wherein the membrane-forming substrate is an ion exchanger comprising one or more uranyl ion complexes of neutral phosphoric acid ester or neutral phosphorous acid ester, and the ion. Uranyl ion electrode that uses a second type electrode as an internal reference electrode, using a sensitive membrane treated with three types of reagents, a diluent that is highly compatible with the exchanger and a solvent that has an affinity with the membrane-forming substrate. 2. A long-life uranyl ion-selective electrode characterized in that potassium chloride is allowed to coexist with uranyl ions as an internal liquid that contacts the sensitive membrane.