CN111821869A

CN111821869A - Lithium ion selective membrane and preparation method thereof

Info

Publication number: CN111821869A
Application number: CN202010606971.6A
Authority: CN
Inventors: 李永波
Original assignee: Genrui Biotech Inc
Current assignee: Genrui Biotech Inc
Priority date: 2020-06-29
Filing date: 2020-06-29
Publication date: 2020-10-27

Abstract

The embodiment of the invention relates to the technical field of chemical analysis, in particular to a lithium ion selective membrane and a preparation method of the lithium ion selective membrane. The lithium ion selective membrane comprises an ionophore comprising 1.9% -2.5% of 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane; an additive comprising 0.05-0.1% potassium tetrakis (4-chlorophenyl) borate; a polymer matrix comprising polyvinyl chloride in an amount of 12% to 16%; a first plasticizer comprising tris (2-ethylhexyl) phosphate in an amount of 8% to 12%; a second plasticizer comprising dioctyl sebacate in an amount of 2% -6%. The lithium ion selective membrane has good linearity and sensitivity of selection of lithium ions and a long life span of the lithium ion selective membrane.

Description

Lithium ion selective membrane and preparation method thereof

Technical Field

The embodiment of the invention relates to the technical field of chemical analysis, in particular to a lithium ion selective membrane and a preparation method of the lithium ion selective membrane.

Background

The use of lithium carbonate has become a good drug for the treatment of mania, but since the therapeutic amount is close to the toxic amount, the lithium concentration in blood should be monitored to control the dosage when lithium carbonate is used. In the past, various methods and techniques have been used for the determination of the concentration of lithium ions in liquid samples, all using large instruments such as high performance liquid chromatography mass spectrometers (HPLC-MS), Atomic Absorption Spectrometers (AAS), inductively coupled plasma atomic emission spectrometers (ICP-OES), inductively coupled plasma mass spectrometers (ICP-MS), and the like. The methods have the disadvantages of complex operation, pretreatment of samples and the like.

The method of potentiometry can be used to test the lithium ion concentration in the liquid and avoid these problems. The apparatus for potentiometrically measuring lithium ions comprises a reference electrode and a lithium ion selective electrode, and when the reference electrode and the lithium ion selective electrode are immersed in a liquid at the same time, a potential is formed therebetween, which is proportional to the logarithm of the lithium ion concentration, and the potential is measured by a potential measuring device such as a potentiometer, and the lithium ion concentration is obtained by measuring the potential. The test method requires that the lithium ion selective membrane from which the lithium ion selective electrode is made be highly selective and unique to lithium ions.

However, in the process of implementing the embodiment of the present invention, the inventors of the present invention found that: CN1419652A discloses a lithium ion selective membrane, wherein the plasticizer is a mixture of 40% -60% of 2-nitrophenyloctyl ether and 5% -15% of trioctylphosphates, the ionophore is about 5% of 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane, and the ionic additive is potassium tetrakis (4-chlorophenyl) borate. Because the content of the plasticizer is excessive, the plasticizer contains 2-nitrophenyloctyl ether, and the performance of the ionic electrode of the PVC membrane, published by Qiao English and the like on a chemical sensor and entitled as the plasticizer, discloses that the selectivity and the response of the 2-nitrophenyloctyl ether (NPOE) to various alkali metal ions are poor, the slope (sensitivity) is lower, and the excessive content of the plasticizer inevitably causes the strength and the toughness of the electrode sensing membrane to be insufficient, the service life to be short and the perforation failure to be easily caused.

Disclosure of Invention

In view of the above, embodiments of the present invention provide a lithium ion selective membrane and a method of manufacturing a lithium ion selective membrane that overcome or at least partially address the above-mentioned problems.

According to an aspect of an embodiment of the present invention, there is provided a lithium ion selective membrane comprising an ionophore comprising 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane in an amount of 1.9% to 2.5%; an additive comprising 0.05-0.1% potassium tetrakis (4-chlorophenyl) borate; a polymer matrix comprising polyvinyl chloride in an amount of 12% to 16%; a first plasticizer comprising tris (2-ethylhexyl) phosphate in an amount of 8% to 12%; a second plasticizer comprising dioctyl sebacate in an amount of 2% -6%.

In an alternative form, the 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane is present in an amount of 1.9%.

In an alternative form, the potassium tetrakis (4-chlorophenyl) borate is present in an amount of 0.05%.

In an alternative form, the tris (2-ethylhexyl) phosphate is present in an amount of 10%.

In an alternative form, the dioctyl sebacate is present in an amount of 4%.

In an alternative form, the polyvinyl chloride content is 14.05%.

According to an aspect of an embodiment of the present invention, there is provided a method of manufacturing a lithium ion selective membrane, including: sequentially adding the first plasticizer, the second plasticizer, an ionophore, an additive and a polymer matrix into a solvent to form a lithium ion selective membrane solution, wherein the first plasticizer comprises tri (2-ethylhexyl) phosphate with the content of 8% -12%, the second plasticizer comprises dioctyl sebacate with the content of 2% -6%, the ionophore comprises 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane with the content of 1.9% -2.5%, the additive comprises potassium tetrakis (4-chlorophenyl) borate with the content of 0.05% -0.1%, and the polymer matrix comprises polyvinyl chloride with the content of 12% -16%; stirring and heating the lithium ion selective membrane solution in water bath; and placing the heated lithium ion selective membrane solution into an electrode cavity for drying to form a membrane.

In an alternative form, the solvent is tetrahydrofuran.

In an alternative form, the tetrahydrofuran is present in an amount of 70% and the total amount of the first plasticizer, second plasticizer, ionophore, additive and polymer matrix is 30%.

According to an aspect of an embodiment of the present invention, there is provided an electrolyte analysis system including an electrolyte analyzer and the above-described lithium ion selective membrane.

The embodiment of the invention has the beneficial effects that: unlike the existing lithium ion selective membrane, the lithium ion selective membrane provided by the embodiment of the present invention includes: an ionophore comprising 1.9% to 2.5% 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane; an additive comprising 0.05-0.1% potassium tetrakis (4-chlorophenyl) borate; a polymer matrix comprising polyvinyl chloride in an amount of 12% to 16%; a first plasticizer comprising tris (2-ethylhexyl) phosphate in an amount of 8% to 12%; a second plasticizer comprising dioctyl sebacate in an amount of 2% -6%. The lithium ion selective membrane is used for detecting the concentration of lithium ions in liquid, and has good linearity, high sensitivity and strong ageing resistance.

Drawings

One or more embodiments are illustrated by way of example in the accompanying drawings, which correspond to the figures in which like reference numerals refer to similar elements and which are not to scale unless otherwise specified.

FIG. 1 is a schematic diagram of the relationship between the potential of a lithium ion selective membrane test lithium ion solution and the logarithm of the lithium ion concentration provided by an embodiment of the invention;

FIG. 2 shows the test results of the sodium ion interference resistance of the lithium ion selective membrane provided by the embodiment of the present invention;

FIG. 3 is a test result of the long-term service life of a lithium ion-selective membrane provided by an embodiment of the present invention;

fig. 4 is a schematic flow chart of a method for preparing a lithium ion selective membrane according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention provides a lithium ion selection membrane, when the lithium ion selection membrane and a reference electrode are immersed into a liquid solution at the same time, a potential is formed between the lithium ion selection membrane and the reference electrode, the potential is in direct proportion to the logarithm of the concentration of lithium ions in the solution, and the concentration of the lithium ions in the solution can be obtained by measuring the potential through a potential measuring device such as a potentiometer.

The lithium ion selective membrane includes an ionophore, an additive, a polymer matrix, a first plasticizer, and a second plasticizer.

As for the above-mentioned ionophores, the ionophores are used to bind lithium ions, transporting a particle stream through the lithium ion selective membrane. The ionophore must be highly selective for lithium ions and avoid interference with sodium ions. Examples of the ionophore include crown ethers such as 14-crown-4-derivatives and 15-crown-4-derivatives; an amino acid; a polypropoxylate adduct; n, N-dicyclohexyl-N ', N' -diisobutyl-cis-cyclohexane-1, 2-dicarboxamide, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane, and the like. Experiments show that when the N, N-dicyclohexyl-N ', N' -diisobutyl-cis-cyclohexane-1, 2-dicarboxamide is used as the ionophore, the ionophore has selectivity on lithium ions, but simultaneously has interference of coexisting Na ions, and the ionophore with high concentration cannot inhibit the interference of the Na ions. Experiments show that when the ionophore is 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane, the ionophore can effectively inhibit Na ion interference in biological body fluid under the condition of higher concentration of the ionophore. The ionic carrier of the embodiment of the invention comprises 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane with the content of 1.9-2.5%, and preferably, the content of the 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane is 1.9%.

For the above additives, the additives need to contribute to the improvement of the conductivity of the lithium ion selective membrane, and have three main functions: the ion electrode induction membrane has Nernst response, the capability of resisting anion interference is enhanced, the membrane internal resistance is reduced, the requirement on the impedance of an electrolyte analyzer is reduced, and the test stability is improved. The additive of the embodiment of the invention comprises potassium tetrakis (4-chlorophenyl) borate in an amount of 0.05-0.1%, and preferably, the potassium tetrakis (4-chlorophenyl) borate is in an amount of 0.05%.

For the polymer matrix to provide mechanical strength and glass transition temperature below room temperature for the lithium ion selective membrane to be formed, and for the polymer matrix to provide particle flux through the lithium ion selective membrane, it is usually combined with the additives, and in the embodiment of the invention, the polymer matrix comprises polyvinyl chloride in an amount of 12% to 16%, preferably 14.05%.

The use of a first and a second plasticizer for the first and second plasticizers described above imparts plasticity to the polymer matrix, renders the polymer matrix an elastic and tough film that enables the flow of particles through the lithium ion selective membrane, while at the same time the first and second plasticizers should be organic solvents that are hydrophobic, highly viscous, and capable of dissolving relatively large amounts of ionophores. The first plasticizer and the second plasticizer are mainly classified into three types, dicarboxylic acid diesters such as dioctyl phthalate, dioctyl sebacate and dioctyl adipate; organic phosphates such as dioctyl phenylphosphate, trioctyl phosphate and the like; nitroaromatic ethers such as o-nitrooctyl ether and the like. Considering that the first plasticizer and the second plasticizer are selective for specific ions, and the first plasticizer, the second plasticizer and the ionophore are lost to some extent as the lithium ion selective membrane is in contact with a solution for a long time, and the loss causes the lithium ion selective membrane to be aged, the first plasticizer of the embodiment of the present invention includes tri (2-ethylhexyl) phosphate in an amount of 8% to 12%, and the second plasticizer includes dioctyl sebacate in an amount of 2% to 6%. Preferably, the content of the phosphoric acid tri (2-ethylhexyl) ester is 10%, and the content of the dioctyl sebacate is 4%.

In order to facilitate a reader to intuitively and better understand the performance and the effect of the lithium ion selection membrane in the embodiment of the invention, the lithium ion selection membrane is subjected to linearity and sensitivity test, repeatability test, sodium ion interference resistance test and long-term service life test.

(1) Linear and sensitivity testing

And placing the electrode made of the lithium ion selective membrane on an electrolyte analyzer to perform linearity and sensitivity tests. Respectively configuring 10 lithium ion solutions with different concentrations, wherein the concentrations are as follows: 0.2mmol/L, 0.4mmol/L, 0.8mmol/L, 1.0mmol/L, 1.5mmol/L, 2.0mmol/L, 4.0mmol/L, 6.0mmol/L, 8.0mmol/L and 10.0mmol/L, each concentration level was tested 3 times separately on the electrolyte analyzer, the potentials were recorded and averaged separately, and the relationship of the potential to the logarithm of the lithium ion concentration was recorded in FIG. 1.

As can be seen from FIG. 1, when the lithium ion concentration is in the range of 0.2mmol/L to 10mmol/L, the concentration of the lithium ion solution is detected by the lithium ion selective membrane, and the logarithm log of the detected potential and lithium ion concentration [ Li]In a linear relationship with a slope of 55.093, R²The results show that the linearity and sensitivity of the lithium ion selective membrane are good at 0.9999.

(2) Repeatability test

And placing the electrode made of the lithium ion selective membrane on an electrolyte analyzer for repeated test. 4 lithium ion solutions with different concentration values were selected. Placing the electrode made of the lithium ion selective membrane in the lithium ion solution for repeatability test, testing each concentration for 20 times, and performing statistical calculation on the test results, wherein the calculation results are shown in the following table 1:

TABLE 1 repeatability test results for lithium ion selective electrodes

	Concentration (mmol/L)	Standard deviation SD (mmol/L)	Coefficient of variation CV
				Lithium ion solution 1	0.45	0.0064	1.42％
Lithium ion solution 2	0.92	0.0032	0.35％
				Lithium ion solution 3	1.32	0.0057	0.43％
Lithium ion solution 4	2.10	0.0072	0.34％

As can be seen from Table 1, the test results show that the standard deviation SD of the lithium ion solution is lower than 0.05 and the coefficient of variation CV of the lithium ion solution is lower than 1.5% after the lithium ion solution is tested for 20 times at each concentration, and the lithium ion selective membrane meets the industrial standard, so that the repeatability of the lithium ion selective membrane is good.

(3) Sodium ion interference resistance test

And placing the electrode made of the lithium ion selective membrane on an electrolyte analyzer to perform a sodium ion interference resistance test. Lithium ion solutions of the same concentration were prepared, to which 1M sodium chloride solution was sequentially added, and potential test values were recorded in fig. 2.

As can be seen from fig. 2, the potential of the lithium ion solution is not changed regardless of the concentration of the sodium ions added to the lithium ion solution, which indicates that the lithium ion electrode film has good resistance to interference by the sodium ions.

(4) Long term service life test

After the electrode is prepared, an ionophore, a first plasticizer and a second plasticizer in the lithium ion selective membrane can run off along with the use of the electrode, so that the sensitivity of the lithium ion selective membrane can be affected, namely, the slope of logarithm log [ Li ] of the potential and the concentration of lithium ions can be reduced, and poor repeatability is further shown, so that the slope is selected as a judgment index, and the service life of the lithium ion selective membrane provided by the embodiment of the invention is tracked. And placing the electrode made of the lithium ion selective membrane in an electrolyte analyzer, ensuring the test quantity of 50-70 samples every day, and recording the slope of the electrode made of the lithium ion selective membrane at irregular intervals. The slope results for a period of 275 days are recorded in figure 3.

As can be seen from fig. 3, the slope of the electrode prepared from the lithium ion selective membrane is mostly higher than 50 in the 275-day test period, and the lowest value of the slope is not lower than 47, so that the long-term service life of the lithium ion selective membrane is good.

The embodiment of the invention provides a lithium ion selective membrane, which comprises an ion carrier, wherein the ion carrier comprises 1.9-2.5% of 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane; an additive comprising 0.05-0.1% potassium tetrakis (4-chlorophenyl) borate; a polymer matrix comprising polyvinyl chloride in an amount of 12% to 16%; a first plasticizer comprising tris (2-ethylhexyl) phosphate in an amount of 8% to 12%; a second plasticizer comprising dioctyl sebacate in an amount of 2% -6%. The lithium ion selective membrane has good linearity and sensitivity of selection of lithium ions and a long life span of the lithium ion selective membrane.

An embodiment of the present invention provides a method for preparing a lithium ion selective membrane, please refer to fig. 4, which includes the following steps:

step S101, sequentially adding the first plasticizer, the second plasticizer, an ion carrier, an additive and a polymer matrix into a solvent to form a lithium ion selective membrane solution, wherein the first plasticizer comprises tri (2-ethylhexyl) phosphate with the content of 8% -12%, the second plasticizer comprises dioctyl sebacate with the content of 2% -6%, the ion carrier comprises 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane with the content of 1.9% -2.5%, the additive comprises potassium tetrakis (4-chlorophenyl) borate with the content of 0.05% -0.1%, and the polymer matrix comprises polyvinyl chloride with the content of 12% -16%.

The solvent is tetrahydrofuran, the content of the tetrahydrofuran is 70%, and the total content of the first plasticizer, the second plasticizer, the ionophore, the additive and the polymer matrix is 30%.

It will be appreciated that the solvent may also be another volatile solvent, for example the solvent may be cyclohexanone.

Preferably, the content of tris (2-ethylhexyl) phosphate is 10%, the content of dioctyl sebacate is 4%, the content of 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane is 1.9%, the content of the additive is 0.05%, and the content of polyvinyl chloride is 14.05%.

And step S102, stirring and heating the lithium ion selective membrane solution in a water bath.

The water bath temperature was 50 ℃ and the heating time was 30 minutes.

And step S103, placing the heated lithium ion selective membrane solution into an electrode cavity to be dried into a membrane.

Wherein the drying time is generally 24 to 48 hours.

It should be noted that, in some embodiments, the lithium ion selective membrane may also be made into a tubular shape, specifically, the heated lithium ion selective membrane solution is coated on the surface of a stainless steel needle, the lithium ion selective membrane solution is coated continuously after the solvent is volatilized, after repeating for 2-9 times until the thickness reaches about 0.6mm, the stainless steel needle is extracted, so as to form a tubular lithium ion selective membrane, and the tubular lithium ion selective membrane may be assembled into an electrode casing to assemble a complete electrode.

It should be noted that, in some embodiments, the lithium ion selective membrane may also be made into a membrane electrode, specifically, the heated lithium ion selective membrane solution is poured into a flat-bottom container with a suitable size, the container material may be glass cup or stainless steel, the container containing the lithium ion motor membrane solution is placed in a dry environment, and after the solvent naturally volatilizes for 24-48 hours, a membrane electrode with a membrane thickness of about 0.5mm is formed. Furthermore, the membrane electrode can be adhered to an electrode shell, and a complete lithium ion measurement system is formed after the corresponding solution and the reference electrode are installed.

It is understood that the lithium ion selective membrane can also be made into other forms of electrodes, such as card electrodes, and the like, and the description of the preparation method of the card electrodes and the like is omitted here.

The embodiment of the invention provides an electrolyte analysis system which comprises an electrolyte analyzer and the lithium ion selective membrane. The electrolyte analyzer in cooperation with the lithium ion selective membrane can test the concentration of lithium ions in a solution.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; within the idea of the invention, also technical features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium ion-selective membrane, comprising:

an ionophore comprising 1.9% to 2.5% 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane;

an additive comprising 0.05-0.1% potassium tetrakis (4-chlorophenyl) borate;

a polymer matrix comprising polyvinyl chloride in an amount of 12% to 16%;

a first plasticizer comprising tris (2-ethylhexyl) phosphate in an amount of 8% to 12%;

a second plasticizer comprising dioctyl sebacate in an amount of 2% -6%.

2. The lithium ion selective membrane of claim 1, wherein the 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane is present in an amount of 1.9%.

3. The lithium ion selective membrane of claim 1, wherein the potassium tetrakis (4-chlorophenyl) borate is present in an amount of 0.05%.

4. The lithium ion selective membrane of claim 1, wherein the tris (2-ethylhexyl) phosphate is present in an amount of 10%.

5. The lithium ion-selective membrane of claim 1, wherein the dioctyl sebacate is present in an amount of 4%.

6. The lithium ion selective membrane of claim 1, wherein the polyvinyl chloride is present in an amount of 14.05%.

7. A method of making a lithium ion selective membrane, comprising:

sequentially adding the first plasticizer, the second plasticizer, an ionophore, an additive and a polymer matrix into a solvent to form a lithium ion selective membrane solution, wherein the first plasticizer comprises tri (2-ethylhexyl) phosphate with the content of 8% -12%, the second plasticizer comprises dioctyl sebacate with the content of 2% -6%, the ionophore comprises 6, 6-dibenzyl-1, 4,8, 11-tetraoxacyclotetradecane with the content of 1.9% -2.5%, the additive comprises potassium tetrakis (4-chlorophenyl) borate with the content of 0.05% -0.1%, and the polymer matrix comprises polyvinyl chloride with the content of 12% -16%;

stirring and heating the lithium ion selective membrane solution in water bath;

and placing the heated lithium ion selective membrane solution into an electrode cavity for drying to form a membrane.

8. The method of claim 7, wherein the solvent is tetrahydrofuran.

9. The method of claim 8, wherein the tetrahydrofuran is present in an amount of 70% and the total amount of the first plasticizer, the second plasticizer, the ionophore, the additive and the polymer matrix is 30%.

10. An electrolyte analysis system comprising an electrolyte analyzer and a lithium ion selective membrane according to any one of claims 1 to 6.