JP2017036234A - Use of compound exhibiting lower limit critical solution temperature type phase behavior - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a use as a temperature sensor or extraction medium of an ion liquid exhibiting LCST behavior and good in thermal stability.SOLUTION: Phosphonium salt represented by the formula (1) can be used as a temperature sensor with a lower limit critical solution temperature as an index in a mixture system with water as it exhibits phase separation behavior having the lower limit critical solution temperature with water and an extraction target can also used as a separation extraction medium by mixing with a water phase containing a separation extraction target and mutually dissolving/phase separating reversibly with temperature control. (1), where Rrepresents an alkyl group having 1 to 30 carbon atoms, Rrepresents an alkyl group or an alkoxy group having 1 to 30 carbon atoms, Rrepresents an alkyl group having 1 to 8 carbon atoms and n represents an integer of 1 to 4.SELECTED DRAWING: None

Description

  The present invention relates to the use of a compound exhibiting a lower critical solution temperature (LCST) type phase behavior (hereinafter sometimes referred to as LCST behavior), and more specifically, phase separation having a lower critical solution temperature with water. The present invention relates to use of a phosphonium salt ionic liquid exhibiting behavior as a temperature sensor or an extraction medium.

  An ionic liquid is a liquid consisting only of ions, and due to the strong electrostatic interaction force acting between the constituent cations and anions, there is almost no vapor pressure and it is nonflammable in a wide temperature range. It has unique properties that are different from molecular liquids such as water and organic solvents, such as maintaining liquid state, greatly changing density, and controlling polarity.

In recent years, there has been reported an ionic liquid capable of constructing an ionic liquid / water mixed system capable of reversibly controlling a compatible state and a phase separation state with a slight temperature change (see, for example, Patent Document 1).
This ionic liquid exhibits a lower critical eutectic temperature type phase behavior that is compatible with cooling when mixed with water. Specifically, in a mixed system with water, phase separation occurs when LCST is exceeded. However, it is a substance capable of reversibly controlling the compatibility / phase separation state depending on the temperature.

  However, since the ionic liquid showing the LCST behavior disclosed in Patent Document 1 is a carboxylate, there is a problem that it is likely to be decomposed by decarboxylation by heat.

JP 2008-44849 A JP 2013-014536 A

  This invention is made | formed in view of such a situation, and it aims at providing the utilization as a temperature sensor and extraction medium of an ionic liquid which shows LCST behavior and favorable thermal stability.

The present inventor has found that a phosphonium salt composed of a predetermined alkylphosphonium cation and a trialkylsilyl group-containing alkylsulfonate anion becomes an ionic liquid, and that the ionic liquid is heat-free even though it is halogen-free. It has already been reported that stability is good and hydrophobicity is shown (Patent Document 2).
Based on this knowledge, as a result of further intensive studies, the present inventor has mixed water with the hydrophobic phosphonium salt ionic liquid and the phosphonium salt ionic liquid having a similar structure in Patent Document 2. In addition, the liquid mixture of the ionic liquid and water can be used as a temperature sensor using LCST as an index, and the ionic liquid can separate the separation and extraction target from the aqueous phase. The present invention has been completed by finding that it can be used as a medium for separation and extraction.

（式中、Ｒ¹は、炭素数１〜３０のアルキル基を表し、Ｒ²は、炭素数１〜３０のアルキル基またはアルコキシ基を表し、Ｒ³は、炭素数１〜８のアルキル基を表し、ｎは、１〜４の整数を表す。）
２． 前記Ｒ¹が、炭素数２〜５の直鎖アルキル基を表し、前記Ｒ²が、炭素数１０〜２０の直鎖アルキル基を表し、前記Ｒ³が、１〜４のアルキル基を表し、前記ｎが、２または３である１の組成物、
３． 前記式（１）で示されるホスホニウム塩が、式（２）〜（５）のいずれかで示される１または２の組成物、

４． 前記下限臨界共溶温度を指標とした温度センサとして用いられる１〜３のいずれかの組成物、
５． 水との下限臨界共溶温度を有する相分離挙動を示す式（１）で示されるホスホニウム塩と、水とを含むことを特徴とする温度センサ、

（式中、Ｒ¹は、炭素数１〜３０のアルキル基を表し、Ｒ²は、炭素数１〜３０のアルキル基またはアルコキシ基を表し、Ｒ³は、炭素数１〜８のアルキル基を表し、ｎは、１〜４の整数を表す。）
６． 分離抽出対象物を含む水相と混合し、温度制御で可逆的に前記水相と相溶／相分離することで前記抽出対象物を分離抽出するための分離抽出媒体であって、水との下限臨界共溶温度を有する相分離挙動を示す式（１）で示されるホスホニウム塩からなることを特徴とする分離抽出媒体、

（式中、Ｒ¹は、炭素数１〜３０のアルキル基を表し、Ｒ²は、炭素数１〜３０のアルキル基またはアルコキシ基を表し、Ｒ³は、炭素数１〜８のアルキル基を表し、ｎは、１〜４の整数を表す。）
７． 分離抽出対象物を含む水相と、６の分離抽出媒体とを混合し、前記下限臨界共溶温度以下で相溶させた後、前記下限臨界共溶温度超まで加温して、前記水相と前記ホスホニウム塩とを相分離させることで、前記分離抽出対象物を前記水相から前記分離抽出媒体中に移行させることを特徴とする分離抽出方法
を提供する。 That is, the present invention
1. A phosphonium salt represented by the formula (1) showing a phase separation behavior having a lower critical eutectic temperature with water and water, and the water and the phosphonium salt are in a phase at a temperature equal to or lower than the lower critical eutectic temperature. A composition characterized by being dissolved,

(In the formula, R ¹ represents an alkyl group having 1 to 30 carbon atoms, R ² represents an alkyl group having 1 to 30 carbon atoms or an alkoxy group, and R ³ represents an alkyl group having 1 to 8 carbon atoms. And n represents an integer of 1 to 4.)
2. R ¹ represents a linear alkyl group having 2 to 5 carbon atoms, R ² represents a linear alkyl group having 10 to 20 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms, 1 composition wherein n is 2 or 3;
3. The phosphonium salt represented by the formula (1) is a composition of 1 or 2 represented by any one of the formulas (2) to (5):

4). Any one of compositions 1 to 3 used as a temperature sensor with the lower critical eutectic temperature as an index;
5). A temperature sensor comprising: a phosphonium salt represented by formula (1) showing a phase separation behavior having a lower critical eutectic temperature with water; and water.

(In the formula, R ¹ represents an alkyl group having 1 to 30 carbon atoms, R ² represents an alkyl group having 1 to 30 carbon atoms or an alkoxy group, and R ³ represents an alkyl group having 1 to 8 carbon atoms. And n represents an integer of 1 to 4.)
6). A separation / extraction medium for separating and extracting the extraction object by mixing with the aqueous phase containing the separation / extraction object and reversibly dissolving / phase-separating with the aqueous phase under temperature control, A separation and extraction medium comprising a phosphonium salt represented by the formula (1) showing a phase separation behavior having a lower critical eutectic temperature;

(In the formula, R ¹ represents an alkyl group having 1 to 30 carbon atoms, R ² represents an alkyl group having 1 to 30 carbon atoms or an alkoxy group, and R ³ represents an alkyl group having 1 to 8 carbon atoms. And n represents an integer of 1 to 4.)
7). The aqueous phase containing the separation / extraction object and the separation / extraction medium of 6 are mixed and dissolved at the lower critical eutectic temperature or lower, and then heated to above the lower critical eutectic temperature, The separation and extraction method is characterized in that the separation and extraction object is transferred from the aqueous phase into the separation and extraction medium by phase-separating the phosphonium salt and the phosphonium salt.

Since the phosphonium salt used in the present invention exhibits LCST behavior in a mixed system with water and is excellent in thermal stability, a high-sensitivity can be obtained by using the LCST as an index after preparing a mixed solution with water. It can be used as a temperature sensor.
In addition, by utilizing the property of the phosphonium salt used in the present invention that is compatible / separated with water, the salt can also be used as a separation / extraction medium for separating and extracting substances dissolved in water. .

3 is a ¹ H-NMR spectrum of ionic liquid 2 synthesized in Synthesis Example 2. FIG. 4 is a ¹ H-NMR spectrum of ionic liquid 4 synthesized in Synthesis Example 4. FIG. It is the graph which plotted LCST in water content 20-80 mass% of the liquid mixture of the ionic liquids 1-4 obtained by the synthesis examples 1-4 and water.

Hereinafter, the present invention will be described in more detail.
The composition according to the present invention comprises a phosphonium salt represented by the formula (1) showing a phase separation behavior having a lower critical solution temperature with water and water, and water at a temperature not higher than the lower critical solution temperature. It is compatible with the phosphonium salt to form a homogeneous system.

Here, R ¹ represents an alkyl group having 1 to 30 carbon atoms, R ² represents an alkyl group having 1 to 30 carbon atoms or an alkoxy group, R ³ represents an alkyl group having 1 to 8 carbon atoms, n represents an integer of 1 to 4.
The alkyl group having 1 to 30 carbon atoms may be linear, branched or cyclic. For example, methyl, ethyl, n-propyl, i-propyl, c-propyl, n-butyl, i-butyl, s- Butyl, t-butyl, c-butyl, n-pentyl, c-pentyl, n-hexyl, c-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, Examples include n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl group and the like.
The alkyl group having 1 to 8 carbon atoms may be linear, branched or cyclic, and among the groups exemplified for the alkyl group having 1 to 30 carbon atoms, the same groups as those having 1 to 8 carbon atoms are used. Can be mentioned.

  As the alkoxy group having 1 to 30 carbon atoms, the alkyl group therein may be linear, branched or cyclic. For example, methoxy, ethoxy, n-propoxy, i-propoxy, c-propoxy, n- Butoxy, i-butoxy, s-butoxy, t-butoxy, c-butoxy, n-pentyloxy, c-pentyloxy, n-hexyloxy, c-hexyloxy, n-heptyloxy, n-octyloxy, 2- Ethylhexyloxy, n-nonyloxy, n-decyloxy, n-undecyloxy, n-dodecyloxy, n-tridecyloxy, n-tetradecyloxy, n-pentadecyloxy, n-hexadecyloxy, n-heptadecyl And oxy, n-octadecyloxy, n-nonadecyloxy, n-eicosyloxy groups, etc. .

Particularly in the present invention, R ¹ is preferably a linear alkyl group having 2 to 8 carbon atoms, more preferably a linear alkyl group having 2 to 5 carbon atoms, and even more preferably a linear alkyl group having 2 to 4 carbon atoms. Preferably, the n-butyl group is optimal in consideration of the characteristics (LCST behavior, heat resistance) and production cost of the ionic liquid used in the present invention.
R ² is preferably a linear alkyl group having 10 to 20 carbon atoms, more preferably a linear alkyl group having 12 to 20 carbon atoms, in consideration of the characteristics of the ionic liquid used in the present invention.
R ³ is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group.
As n, 1-8 are preferable, 2-6 are more preferable, and 2 or 3 is still more preferable.

Since the phosphonium salt (ionic liquid) shows a specific LCST in a specific ratio with water, as shown in the following examples, it is used as a highly sensitive temperature sensor by using the cloudiness point in the LCST as an index. can do.
In this case, the mixing ratio of the phosphonium salt and water is appropriately set according to the temperature to be measured within the range showing the LCST behavior, but in the present invention, water: phosphonium salt = 1 by mass ratio. : About 9 to 9: 1, and preferably used as a temperature sensor in a mixed system of about 2: 8 to 8: 2.
In addition, when using as a temperature sensor, in order to prevent the fluctuation | variation of LCST by evaporation of water, it is preferable to seal and use the liquid mixture of phosphonium salt and water.

As described in Patent Document 2, the phosphonium salt used in the present invention includes a trialkylsilyl group-containing alkyl sulfonate and a tetraalkylphosphonium halide represented by R ¹ ₃ R ² PX (X is a halogen atom). And cation exchange between a trialkylsilyl group-containing alkyl sulfonate and a tetraalkylphosphonium salt represented by R ¹ ₃ R ² PX (where X is a halogen atom). After conversion into a trialkylsilyl group-containing alkylsulfonic acid and a tetraalkylphosphonium hydroxide using a resin and an anion exchange resin, it can be obtained by a neutralization method in which both are mixed.
In this case, sodium salt, potassium salt, silver salt and the like can be used as the sulfonate.
In addition, examples of the halogen atom include fluorine, chlorine, bromine and iodine atoms, with a chlorine atom and bromine atom being preferred.
The solvent may be either water or an organic solvent, but the produced ionic liquid exhibits LCST behavior and is separated into water and two layers at a temperature exceeding the LCST. Operations such as purification become easy.

The use ratio of R ¹ ₃ R ² PX (X is a halogen atom) and the trialkylsilyl group-containing alkyl sulfonate in the above reaction can be about 5: 1 to 1: 5 in molar ratio. Usually, it is preferable to carry out at a ratio close to 1: 1.
After completion of the reaction, the desired product can be obtained by carrying out usual post-treatment.

  The phosphonium salt used in the present invention can also be used as a medium for separating and extracting substances dissolved in the aqueous phase by utilizing the LCST behavior when mixed with water. As a separation / extraction method, an aqueous phase containing a separation / extraction object and a phosphonium salt represented by the above formula (1) were mixed and cooled to LCST or lower (above the freezing point of the phosphonium salt) to make them compatible. Thereafter, the mixture is heated up to LCST and the aqueous phase and the phosphonium salt are phase-separated to transfer the separation / extraction object from the aqueous phase into the phosphonium salt.

There is no particular limitation on the mixing method, and either the aqueous phase may be added to the phosphonium salt or the phosphonium salt may be added to the aqueous phase. May be. Further, the temperature during mixing may be set to LCST or lower.
In this case, the mixing ratio of the water containing the separation and extraction object and the phosphonium salt is not particularly limited as long as it is in a range showing LCST behavior, but from the viewpoint of separation and extraction efficiency and workability, the mass ratio And water: phosphonium salt = 1: 9 to 9: 1, preferably 2: 8 to 8: 2, and more preferably 2: 8 to 4: 6.

The separation / extraction object is not particularly limited as long as it has a property of transferring from a water phase to a phosphonium salt in the water / phosphonium salt mixed liquid having the above-mentioned ratio, and examples thereof include proteins and enzymes.
It is also possible to separate the metal species dissolved in water from the aqueous system by previously dissolving the component that forms a complex with the metal species in the phosphonium salt as a complex-forming agent and carrying out this method. In this case, the component that normally forms a complex is an organic substance and is easily dissolved in a phosphonium salt that is an organic ionic liquid, but its solubility in water is poor. For this reason, the target metal species can be extracted more efficiently by the present method in which the system is once made homogeneous than when it is extracted in the presence of a normal organic solvent.
By using this method, for example, a rare metal can be selectively extracted. In an aqueous solution system mixed with other metal species such as a waste liquid, a ligand that preferentially forms a complex with a desired rare metal is previously converted to phosphonium. If dissolved in a salt system, the desired rare metal can be completely extracted from the aqueous layer by adjusting the amount of the ligand.

  Known complex forming agents can be used, such as TBP (tri-n-butyl phosphate), DBBP (di-n-butyl-n-butyl phosphate), TOP (tri-n-octyl phosphate), P-350 (dimethylheptylmethyl phosphate), CMPO (n-octyl (phenyl) -N, N-diisobutylcarbamoylmethyl) phosphine oxide, TOPO (trioctylphosphine oxide), TOA (tri-n-octylamine) and the like can be mentioned. However, among them, it is preferable to use TBP because rare earth elements can be extracted efficiently and compatibility with the ionic liquid of the present invention is good.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limited to the following Example.
The analyzers and conditions used in the examples are as follows.
[1] ¹ H-NMR spectrum apparatus: AL-400 manufactured by JEOL Ltd.
Solvent: deuterated chloroform [2] melting point apparatus: DSC 6200 manufactured by Seiko Instruments Inc.
Measurement conditions: 10 ° C./min from 20 ° C. to 60 ° C., 1 ° C./min from 60 ° C. to −90 ° C., 1 min per minute from −90 ° C. to 60 ° C. after holding at −90 ° C. for 1 min. Measured under temperature conditions.
[3] Disassembly point device: TG-DTA 6200 manufactured by Seiko Instruments Inc.
Measurement conditions: Measurement was performed at 30 ° C. to 500 ° C. under a temperature increase of 10 ° C. per minute in an air atmosphere, and the temperature at which the mass decreased by 10% was taken as the decomposition point.
[4] LCST temperature measuring device: HFT-40 (Anri Keiki Co., Ltd.)
[5] Metal ion concentration apparatus: ICA-2000 manufactured by Toa DKK Corporation
Measurement conditions: separation column PCI-321, guard column PCI-321G, eluent methanesulfonic acid 2 mM water-acetonitrile (1: 1) mixed solvent, flow rate 0.8 mL / min

[1] Synthesis of ionic liquid [Synthesis Example 1] Synthesis of ionic liquid 1

1.00 g of sodium 3- (trimethylsilyl) -1-propanesulfonate (manufactured by Sigma-Aldrich) was dissolved in 120 mL of ion-exchanged water. A solution prepared by previously dissolving 2.28 g of tributylhexadecylphosphonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) in 80 mL of ion-exchanged water was added to this solution and stirred overnight at room temperature. At this time, the reaction solution became cloudy at first and separated into two layers when allowed to stand after reaction overnight. 50 mL of ethyl acetate (manufactured by Wako Pure Chemical Industries, Ltd.) was added to this reaction solution, and the organic layer was extracted. This operation was further repeated twice, and the combined organic layer was washed twice with 50 mL of ion exchange water. About 20 g of potassium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) is added to the organic layer and dried. After solids are filtered off, the solvent is distilled off to obtain the target ionic liquid 1 (BHDP · DSS). 2.12 g was obtained as a colorless transparent liquid (yield 77%). When this ionic liquid 1 was mixed with an equal volume of water, it was completely separated into two layers and confirmed to be hydrophobic.
Further, the melting point of the ionic liquid 1 was −5 ° C., and the decomposition point was 299 ° C. (10%).

[Synthesis Example 2] Synthesis of ionic liquid 2

The ionic liquid 2 (BHDP · TMSES) was colorless in the same manner as in Synthesis Example 1 except that sodium 2- (trimethylsilyl) -1-ethanesulfonate was used instead of sodium 3- (trimethylsilyl) -1-propanesulfonate. Obtained as a clear liquid (68% yield). Incidentally, sodium 2- (trimethylsilyl) -1-ethanesulfonate was synthesized according to the method described in US Pat. No. 3,141,898. A ¹ H-NMR spectrum of the ionic liquid 2 is shown in FIG. When this ionic liquid 2 was mixed with an equal volume of water, it was completely separated into two layers and confirmed to be hydrophobic.
Further, the melting point of the ionic liquid 2 was 5 ° C., and the decomposition point was 316 ° C. (10%).

[Synthesis Example 3] Synthesis of ionic liquid 3

Except for using tributyl dodecyl phosphonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) instead of tributyl hexadecyl phosphonium bromide, ionic liquid 3 (BDDP · DSS) was obtained as a colorless transparent liquid in the same manner as in Synthesis Example 1 ( Yield 70%). When this ionic liquid 3 was mixed with an equal volume of water, it was completely separated into two layers and confirmed to be hydrophobic.
The melting point of the ionic liquid 3 was 2 ° C., and the decomposition point was 291 ° C. (10%).

[Synthesis Example 4] Synthesis of ionic liquid 4

Except for using tributyl dodecyl phosphonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) instead of tributyl hexadecyl phosphonium bromide, ionic liquid 4 (BDDP • TMSES) was obtained as a colorless transparent liquid in the same manner as in Synthesis Example 2 ( Yield 68%). The ¹ H-NMR spectrum of ionic liquid 4 (apparatus: AL-400 manufactured by JEOL Ltd., solvent: deuterated chloroform) is shown in FIG. When this ionic liquid 4 was mixed with an equal volume of water, it was completely separated into two layers and confirmed to be hydrophobic.
The melting point of the ionic liquid 4 was −6 ° C., and the decomposition point was 311 ° C. (10%).

[2] Confirmation of LCST behavior [Example 1-1]
The mixture was ice-cooled with ion-exchanged water and ionic liquid 1 (BHDP · DSS) obtained in Synthesis Example 1 in the proportions shown in Table 1, and it was confirmed that the solution was uniform.
Thereafter, in order to monitor the liquid temperature, ice cooling was stopped in a state where a thermocouple was inserted into each solution, and the temperature (LCST) at which white turbidity was generated by raising the temperature naturally while stirring was measured. The results are shown in Table 1. The graph which plotted LCST in the water content 20-80 mass% of the liquid mixture of the ionic liquid 1 and water is shown in FIG.
When stirring was stopped at each LCST, it was confirmed that the ion-exchanged water and the ionic liquid 1 were separated into two layers and were cooled again on ice to form a homogeneous solution.

[Examples 1-2 to 1-4]
The ionic liquid 1 was changed to the ionic liquid 2 (BHDP · TMSES), the ionic liquid 3 (BDDP · DSS), and the ionic liquid 4 (BDDP · TMSES) obtained in Synthesis Examples 2 to 4, and each of the ionic liquid 1 was changed to Example 1. The same experiment was conducted and LCST was measured. The results are also shown in Table 1. Moreover, the graph which plotted LCST in the water content 20-80 mass% of the liquid mixture of the ionic liquids 2-4 and water is combined with FIG. 3, and is shown.
In addition, when stirring was stopped by each LCST, each of ion-exchange water and the ionic liquids 2-4 isolate | separated into two layers, and it confirmed that it became a homogeneous solution by ice-cooling again.

As described above, the ionic liquids 1 to 4 are excellent in heat resistance, and in any of the ionic liquids 1 to 4, LCST is obtained when a mixture with ion-exchanged water (water content 20 to 80% by mass) is used. It can be seen that it is an ionic liquid that can be reversibly phase-separated and compatible with water by changing the temperature.
By utilizing this phase separation / compatibility, enzymes, proteins, rare metals and the like dissolved in water can be extracted.
In addition, since the ionic liquid of the present invention shows a specific LCST in a specific ratio with water, it can be used as a high-sensitivity temperature sensor in units of 0.1 ° C. by using the white cloud point in the LCST as an index. .

[3] Example of rare metal recovery 0.3 g of europium chloride hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) is added to 30 mL of ion-exchanged water contained in a 50 mL sample tube and completely dissolved by shaking. It was. 10 mL of this was divided into two 50 mL sample tubes, and 10 mL of ionic liquid 3 (BDDP / DSS) containing 5% by mass of TBP (tri-n-butyl phosphate) (manufactured by Kanto Chemical Co., Ltd.) On the other hand, 10 mL of ethyl acetate (manufactured by Kanto Chemical Co., Inc.) containing 5% by mass of TBP was added.
The sample tube to which the TBP-BDDP / DSS solution was added was shaken and then put into a refrigerator to be cooled. After confirming that the solution was uniform, the solution was taken out from the refrigerator and the liquid was transferred to a separatory funnel. The liquid temperature rose as it was, and it was left until it was separated into two layers. Then, liquid separation operation was performed and the lower layer aqueous layer was isolate | separated from the upper layer.
The sample tube to which the TBP-ethyl acetate solution was added was shaken well, then transferred to a separatory funnel to perform a liquid separation operation, and the lower aqueous layer was separated from the upper layer.
Each separated aqueous layer was subjected to anion chromatography analysis. Table 2 shows the result of comparison with the analytical value of the europium chloride hexahydrate aqueous solution before addition of the 5 mass% TBP solution.

  As shown in Table 2, when the 5% TBP BDDP / DSS solution was added, the rare earth element europium was almost completely extracted from the aqueous layer, whereas the one extracted with the ethyl acetate solution was slightly Europium remains, indicating that BDDP · DSS is superior in extraction ability.

Claims (7)

A phosphonium salt represented by the formula (1) showing a phase separation behavior having a lower critical eutectic temperature with water and water, and the water and the phosphonium salt are in a phase at a temperature equal to or lower than the lower critical eutectic temperature. A composition characterized by being dissolved.

(In the formula, R ¹ represents an alkyl group having 1 to 30 carbon atoms, R ² represents an alkyl group having 1 to 30 carbon atoms or an alkoxy group, and R ³ represents an alkyl group having 1 to 8 carbon atoms. And n represents an integer of 1 to 4.) R ¹ represents a linear alkyl group having 2 to 5 carbon atoms, R ² represents a linear alkyl group having 10 to 20 carbon atoms, R ³ represents an alkyl group having 1 to 4 carbon atoms, The composition according to claim 1, wherein n is 2 or 3. The composition according to claim 1 or 2, wherein the phosphonium salt represented by the formula (1) is represented by any one of the formulas (2) to (5).

  The composition according to any one of claims 1 to 3, which is used as a temperature sensor using the lower critical eutectic temperature as an index. A temperature sensor comprising: a phosphonium salt represented by formula (1) showing a phase separation behavior having a lower critical solution temperature with water; and water.

(In the formula, R ¹ represents an alkyl group having 1 to 30 carbon atoms, R ² represents an alkyl group having 1 to 30 carbon atoms or an alkoxy group, and R ³ represents an alkyl group having 1 to 8 carbon atoms. And n represents an integer of 1 to 4.) A separation / extraction medium for separating and extracting the extraction object by mixing with the aqueous phase containing the separation / extraction object and reversibly dissolving / phase-separating with the aqueous phase under temperature control,
A separation and extraction medium comprising a phosphonium salt represented by the formula (1) showing a phase separation behavior having a lower critical solution temperature with water.

(In the formula, R ¹ represents an alkyl group having 1 to 30 carbon atoms, R ² represents an alkyl group having 1 to 30 carbon atoms or an alkoxy group, and R ³ represents an alkyl group having 1 to 8 carbon atoms. And n represents an integer of 1 to 4.)   The aqueous phase containing the separation and extraction object is mixed with the separation and extraction medium according to claim 6, mixed at a temperature lower than or equal to the lower critical eutectic temperature, and then heated to above the lower critical eutectic temperature, A separation / extraction method, wherein the separation / extraction object is transferred from the aqueous phase into the separation / extraction medium by phase separation of the aqueous phase and the phosphonium salt.

Images