CN111537456B

CN111537456B - Application of ionic liquid aqueous two-phase system in determination of organic matter hydrophobicity

Info

Publication number: CN111537456B
Application number: CN202010387577.8A
Authority: CN
Inventors: 瞿晓磊; 刘昆; 王佳雪; 付翯云
Original assignee: Nanjing University
Current assignee: Nanjing University
Priority date: 2020-05-09
Filing date: 2020-05-09
Publication date: 2021-09-17
Anticipated expiration: 2040-05-09
Also published as: CN111537456A

Abstract

The invention discloses an application of an ionic liquid double-water-phase system in determination of organic matter hydrophobicity, wherein the ionic liquid double-water-phase system is formed by imidazole ionic liquid and inorganic salt water solution and is provided with a solution with upper and lower two-phase layering, and the absorbance or absorbance integral value ratio of organic matter in the upper phase solution and the lower phase solution is determined to obtain a distribution coefficient (K)_ATPS) And determining the hydrophobicity of the organic matter. The method has the characteristics of rapidness, simplicity, low cost, no dependence on complex instruments and environmental friendliness; the quantity of samples required by determination is small, and the enzyme-labeling instrument replaces an ultraviolet spectrophotometer to carry out detection, so that high-throughput detection of the samples can be realized, and a foundation is laid for realizing high-throughput detection and potential automation of hydrophobicity of organic matters.

Description

Application of ionic liquid aqueous two-phase system in determination of organic matter hydrophobicity

Technical Field

The invention belongs to the field of organic matter determination, and particularly relates to application of an ionic liquid two-aqueous-phase system in determination of organic matter hydrophobicity.

Background

Organic matter is a decomposition product of animal and plant residues and a complex mixture thereof synthesized through biochemical action, and is ubiquitous in land and water environments. The hydrophobicity of organic matter is one of the most basic properties, it affects many of the geochemical processes of importance in the environment, the distribution of organic pollutants on organic matter, and thus its transportation, fate and bioavailability in the environment, and the adsorption and aggregation behavior of organic matter on geological adsorbents, and plays an important role in the circulation and export of carbon and other elements. From an engineering perspective, the hydrophobicity of organic matter can affect the performance of many water treatment unit processes, such as the formation of membrane systems and disinfection byproducts.

The hydrophobicity of organic matter is not easily quantified and currently common methods include fractional distillation, elemental analysis, Nuclear Magnetic Resonance (NMR) and reverse phase High Performance Liquid Chromatography (HPLC). Adsorption of organic matter on XAD resins was originally used to separate organic matter from natural water, and it was also used to separate the hydrophobic, transitional, and hydrophilic portions of organic matter, with percentages of each portion being indicative of overall hydrophobicity, but the fractionation process is time consuming and laborious. The elemental composition of organic matter (e.g., O/C and (O + N)/C) is widely used to characterize the polarity/hydrophobicity of organic matter. However, this method requires a large sample of separated organic matter powder, which requires a great deal of effort to concentrate, separate and purify the organic matter from water and soil. Solid state¹³C NMR is a powerful method for quantitatively characterizing organic matter. It is reported that structural components of organic matter, such as aromatic carbon and aliphatic carbon, are related to the ability thereof to adsorb polycyclic aromatic hydrocarbons. However, this method requires a complicated analysis instrument and experienced personnel. Solid state NMR analysis also requires sorting through a large sample of organic matter powder in order to characterize the aquatic organic matter. Reverse phase HPLC can be used to measure the polarity/hydrophobicity of organic components based on a dynamic equilibrium process between the organic component and the stationary phase, but still relies on complex instrumentation and is influenced by the selection of reference materials and operating conditions. Furthermore, this method does not quantify the overall hydrophobicity of organic matter. Some spectral indicators have been reported to correlate with the aromaticity of organic matter, e.g., SUVA₂₅₄，E₄/E₆And humification index. However, these indirect relationships are less reliable for quantifying the hydrophobicity of organic matter and are more useful for semi-quantitative analysis. Because the traditional method has the defects of time and labor waste, large-scale instruments, certain operation experience and inaccurate characterization method in the measurement of the hydrophobicity of the organic matters, a new method which is simple, convenient, green and environment-friendly and does not need complex instruments for measuring the hydrophobicity of the organic matters is urgently needed to be developed at present.

Disclosure of Invention

The invention aims to establish a simple, convenient and high-flux measuring method for measuring the hydrophobicity of organic matters, which measures the hydrophobicity of the organic matters by using a two-aqueous-phase system formed by two immiscible aqueous solutions.

The present inventors have discovered a method commonly used to characterize the hydrophobicity of organic contaminants: the n-octanol-water system cannot be applied to characterization of organic matter hydrophobicity. Here we propose to use an aqueous two-phase system (ATPS) as a simple and reliable method to quantify organic hydrophobicity. Aqueous two-phase systems are generally based on two immiscible water-rich phases of a polymer-polymer, polymer-salt or ionic liquid-salt combination, i.e. two water-soluble substances which, after mixing in a certain concentration ratio, form two mutually immiscible phases, one of which is rich in one of the substances and the other of which is generally rich in one of the polymers or salts. Due to their biocompatibility, simplicity and low cost, they are widely used for the separation and purification of biological materials (e.g., cells, membranes and proteins). Factors that influence the partitioning of a compound in aqueous two phases mainly include its hydrophobicity, surface charge, size, conformation and biospecific affinity. Among other things, hydrophobic effects play a key role in determining partition coefficients. The invention relates to K_ATPSAs a practical measurement of the hydrophobicity of the organic matter, a reliable method for measuring the hydrophobicity of the organic matter with high flux is established by utilizing an ionic liquid two-aqueous phase system.

Specifically, the organic matter includes, but is not limited to, humic substances, specifically humic acid, and the like.

Preferably, the ionic liquid aqueous two-phase system is a solution formed by layering an upper phase and a lower phase and formed by an aqueous solution of the imidazole ionic liquid and an aqueous solution of an inorganic salt.

Preferably, the volume ratio of the aqueous solution of the imidazole ionic liquid to the aqueous solution of the inorganic salt is 1 (1-2), wherein the concentrations of the aqueous solution of the imidazole ionic liquid and the aqueous solution of the inorganic salt are only required to meet the requirement of phase separation.

More preferably, the imidazole ionic liquid is [ C ]₂mim]Br、[C₄mim]Br、[C₆mim]Br、[C₈mim]Br、[C₁₀mim]Br、[C₂mim]Cl、[C₄mim]Cl、[C₆mim]Cl、[C₈mim]Cl、[C₁₀mim]Any ionic liquid of Cl, most preferably [ C₄mim]Br。

The inorganic salt is any one of phosphate, carbonate, citrate, Rochelle salt, chloride salt, fluoride salt, acetate and hydroxide.

Most preferably, the ionic liquid aqueous two-phase system is composed of [ C₄mim]The aqueous solution of Br and the aqueous solution of phosphate form a solution with upper and lower two phases separated.

Further, the invention provides a specific method for measuring organic matter hydrophobicity by using the ionic liquid aqueous two-phase system, which comprises the following steps:

(1) preparing an ionic liquid double-water-phase system with upper and lower two-phase layering;

(2) adding an aqueous solution of an organic matter to be detected into the ionic liquid aqueous two-phase system in the step (1), fully mixing, standing to form a layered solution of an upper phase and a lower phase, and respectively measuring an absorbance value corresponding to any wavelength of the upper phase and the lower phase in a 255-270 nm interval or an absorbance integral value corresponding to a wavelength of a certain waveband in the interval by using an enzyme-labeling instrument;

(3) adding deionized water with the same volume as the aqueous solution of the organic matters into the ionic liquid aqueous two-phase system in the step (1) for full mixing, standing to form layered solutions of an upper phase and a lower phase, and respectively measuring background absorbance values or background absorbance integral values of the upper phase and the lower phase at corresponding wavelengths by using an enzyme-labeling instrument;

(4) correspondingly subtracting the absorbance values or absorbance integral values respectively measured by the upper phase and the lower phase in the step (2) from the background absorbance values or background absorbance integral values respectively measured by the upper phase and the lower phase in the step (3) to obtain the actual absorbance of the upper phase and the lower phase, and calculating the ratio of the actual absorbance of the upper phase to the actual absorbance of the lower phase as the distribution coefficient K of the organic matter in the aqueous two phases_ATPSThrough K_ATPSAs a practical measure of the hydrophobicity of organic matter.

Further, in the step (2), the volume ratio of the aqueous solution of the organic matter to the ionic liquid double-water-phase system is (0.3-2) to (2-8).

Preferably, in the step (2), absorbance values corresponding to the upper and lower phases at a wavelength of 270nm or 260nm, or absorbance integral values corresponding to a wavelength interval of 255-265nm are respectively measured.

Compared with the existing method for measuring the hydrophobicity of the organic matter, the method has the following beneficial effects:

(1) the method designed by the invention does not need centrifugal operation, and has the characteristics of rapidness, simplicity, low cost, no dependence on complex instruments and environmental friendliness.

(2) The determination method of the invention requires less sample amount; the enzyme-labeling instrument replaces an ultraviolet spectrophotometer to detect, so that high-flux detection of a sample can be realized, and a foundation is laid for realizing high-flux detection and potential automation of organic matter hydrophobicity.

Drawings

The foregoing and/or other advantages of the invention will become further apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

FIG. 1 is a process schematic diagram of measuring organic matter hydrophobicity by an ionic liquid aqueous two-phase system.

FIG. 2 shows example 1[ C ]₄mim]Aqueous solution of Br and K₂HPO₄With KH₂PO₄Phase diagram of the mixed aqueous solution.

Fig. 3 is a fitting graph based on the above two-water phase distribution coefficient and organic matter element analysis in example 1.

Fig. 4 is a fitting graph based on the above dual water phase distribution coefficient and organic matter structure parameter in example 1.

Fig. 5 is a graph of the fit of the double water phase partition coefficient and the free energy of interaction between organic molecules in example 1.

Fig. 6 is a graph of the organic carbon normalized partition coefficient (Koc) fit based on the above-described two-water phase partition coefficient and organic matter of example 1.

Fig. 7 is a fitting graph based on the above two-water phase distribution coefficient and organic matter element analysis in example 2.

Fig. 8 is a fitting graph based on the above dual-water phase distribution coefficient and organic matter structure parameter in example 2.

FIG. 9 is a graph of the fitting of the double water phase partition coefficient and the free energy of interaction between organic molecules in example 2.

Fig. 10 is a fitting graph based on the above two-water phase distribution coefficient and organic matter element analysis in example 3.

Fig. 11 is a fitting graph based on the above dual water phase distribution coefficients and organic matter structure parameters in example 3.

Fig. 12 is a fitting graph of the double water phase partition coefficient and the free energy of interaction between organic molecules in example 3.

Fig. 13 is a fitting graph based on the above two-water phase distribution coefficient and organic matter element analysis in example 4.

Fig. 14 is a fitting graph based on the above dual water phase distribution coefficients and organic matter structure parameters in example 4.

Fig. 15 is a graph of example 4 based on the above fit of the double water phase partition coefficient and the free energy of interaction between organic molecules.

Fig. 16 is a fitting graph of the double water phase distribution coefficient and organic matter element analysis in example 5.

Fig. 17 is a fitting graph based on the above dual-water phase distribution coefficient and organic matter structure parameter in example 5.

Fig. 18 is a graph of the fit of the double water phase partition coefficient and the free energy of interaction between organic molecules in example 5.

Fig. 19 is a fitting graph based on the above two-water phase distribution coefficient and organic matter element analysis in example 6.

Fig. 20 is a fitting graph based on the above dual-water phase distribution coefficient and organic matter structure parameter in example 6.

Fig. 21 is a graph of example 6 based on the above fit of the two-water phase partition coefficient and the free energy of interaction between organic molecules.

Detailed Description

The invention will be better understood from the following examples.

The principle process of measuring the hydrophobicity of the organic matter by using the ionic liquid aqueous two-phase system in the embodiment is shown in fig. 1:

(1) preparing an aqueous solution of imidazole ionic liquid and an aqueous solution of inorganic salt, and then mixing to form an ionic liquid two-water-phase system with upper and lower two phases separated;

(3) replacing the aqueous solution of the organic matter to be detected with deionized water, adding the aqueous solution into the ionic liquid aqueous two-phase system obtained in the step (1), fully mixing, standing to form a layered solution of an upper phase and a lower phase, and respectively measuring background absorbance values or background absorbance integral values of the upper phase and the lower phase at corresponding wavelengths by using an enzyme-labeling instrument; (ii) a

(4) Correspondingly subtracting the background absorbance values or the background absorbance integral values respectively measured by the upper phase and the lower phase in the step (3) from the absorbance values or the absorbance integral values respectively measured by the upper phase and the lower phase in the step (2) to obtain the actual absorbance of the upper phase and the lower phase, and calculating the ratio of the actual absorbance of the upper phase to the actual absorbance of the lower phase to obtain K_ATPS。

The method can simultaneously measure the upper phase and the lower phase of 1 blank sample and the upper phase and the lower phase of 47 samples by utilizing a 96-pore plate and an enzyme-labeling instrument, ensures that 47 samples can be simultaneously processed by single measurement, and has greatly improved efficiency compared with the condition that only 1 sample can be measured by a polymer-salt system at a time.

Example 1

Determining [ C ] from the phase diagram shown in FIG. 2₄mim]Br (IL) Ionic liquid aqueous solution concentration and K₂HPO₄With KH₂PO₄The concentration of the aqueous solution. For [ C ]₄mim]Br/(KH₂PO₄+K₂HPO₄) The two aqueous phase diagram (two-segment line) was determined by cloud point titration. The specific experimental steps are as follows: (1) and placing the prepared ionic liquid solution and the prepared salt solution into a blue-cap bottle, and weighing for later use. (2) Weighing a certain amount of (KH) at room temperature₂PO₄+K₂HPO₄) Placing the stock solution in a 15ml centrifuge tube; (3) dropwise adding the ionic liquid solution into a 15ml centrifuge tube, stirring until turbidity appears, and determining the addition of the ionic liquidThe amount of body, and vice versa; and calculating to obtain the composition of the mixture, namely obtaining a composition point on the binodal line. (4) Adding a small amount of water into the double water phase system until the turbidity disappears, weighing, and repeating the operation to obtain enough double nodes. The upper phase was finally determined to be 50 wt% [ C ]₄mim]Br ion liquid aqueous solution, the lower phase is 10 wt% KH₂PO₄And 30 wt% K₂HPO₄An aqueous solution of inorganic salts.

In the experiments, the aqueous two-phase partitioning experiments were carried out using standard humic acid samples from the American humic acid society, and the specific humic acid configuration experimental procedures were as follows: mixing 40mg of humic acid solid sample and 200ml of deionized water in a 250ml blue-covered bottle, adding a small amount of 1mol/L aqueous alkali to the insoluble humic acid sample for assisting dissolution, adjusting the pH of the humic acid solution to be neutral by using an HCl solution after ultrasonic treatment for 5min, standing in the dark for 24h, and then measuring the pH again to ensure that the humic acid solution is neutral. And filtering the pH-adjusted humic acid solution with a 0.45-micron filter membrane, bottling the filtered solution and placing in a refrigerator at 4 ℃ for later use. When the solution is to be used, various humic acid solutions to be tested are diluted to 15mgC/L for distribution experiments.

Taking 1.5ml of [ C ]₄mim]Fully mixing Br ionic liquid aqueous solution, 1.5ml inorganic salt aqueous solution and 0.75ml organic matter solution, standing for 1h, and sampling to determine the absorbance value of the organic matter at 270nm position in the upper phase and the lower phase after distribution and balance.

At the same time, the organic matter solution was replaced with 0.75ml of deionized water, and 1.5ml of C₄mim]Fully and uniformly mixing a Br ionic liquid aqueous solution and 1.5ml of an inorganic salt aqueous solution, standing at a constant temperature, and sampling to determine the background absorbance value of the organic matter at 270nm in the upper phase and the lower phase.

Subtracting the background absorbance value to calculate the actual absorbance of the upper phase and the lower phase, and dividing the actual absorbance of the upper phase by the actual absorbance of the lower phase to obtain the distribution coefficient K of the organic matter in the aqueous two phases_ATPS。

Fig. 3 shows the analytical fitting of the two aqueous phase distribution coefficients and organic matter elements: wherein, the element ratio (O + N/C) and O/C can both represent the polarity condition of humic acid, i.e. the higher the element ratio, the stronger the polarity and the weaker the hydrophobicity. It can be seen from the figure that the above-mentioned two-aqueous phase distribution coefficients all show a good inverse relationship with the ratio of these two elements.

Fig. 4 is a fitting method based on the double water phase distribution coefficient and organic matter structure parameters: wherein, aromatic carbon and aromatic carbon + aliphatic carbon can both represent the hydrophobicity condition of humic acid, namely, the higher the carbon content is, the stronger the hydrophobicity of humic acid is. It can be seen from the figure that the above dual-water phase distribution coefficient shows a good positive correlation with the two structural parameters.

Fig. 5 shows the fitting of the free energy based on the interaction between the double water phase distribution coefficient and the organic matter molecules: wherein the free energy of intermolecular interaction can also be used as a parameter for characterizing the hydrophobicity of the humic acid. It can be seen from the figure that the double water phase distribution coefficients and the intermolecular interaction free energy show a good inverse relationship.

FIG. 6 is a fitting to Koc based on the above two-water phase partition coefficients: the pyrene adsorption process of the organic matters proves that the main acting force is hydrophobic effect, so that the Koc size of pyrene adsorption of the organic matters can reflect the hydrophobic size of the organic matters to a certain extent. It can be seen from the figure that the double water phase distribution coefficient and the adsorption coefficient show a good positive correlation.

Example 2

Preparing 50% (w/w) [ C ]₄mim]Br solution and 40 wt% K₃PO₄And mixing the solutions to obtain an ionic liquid aqueous two-phase system.

2.5ml of [ C ] was taken₄mim]Aqueous Br ion liquid solution, 4ml40wt％K₃PO₄And fully mixing the solution with 2ml of organic matter solution, standing for 1h at a constant temperature of 20 ℃, sampling after distribution and balance, and measuring the absorbance value of the organic matter at the position of 260nm in the upper phase and the lower phase.

At the same time, the organic matter solution was replaced with 2ml of deionized water, and 2.5ml of [ C ]₄mim]Br Ionic liquid aqueous solution, 4ml40 wt% K₃PO₄And fully and uniformly mixing the solution, standing at constant temperature, and sampling to determine the background absorbance value of the organic matter at 260nm in the upper phase and the lower phase.

Fig. 7 shows the analytical fitting of the two aqueous phase distribution coefficients and organic matter elements: wherein, the element ratio (O + N/C) and O/C can both represent the polarity condition of humic acid, i.e. the higher the element ratio, the stronger the polarity and the weaker the hydrophobicity. It can be seen from the figure that the above-mentioned two-aqueous phase distribution coefficients all show a good inverse relationship with the ratio of these two elements.

Fig. 8 shows the fitting of the double water phase distribution coefficient and the organic matter structure parameter: wherein, aromatic carbon and aromatic carbon + aliphatic carbon can both represent the hydrophobicity condition of humic acid, namely, the higher the carbon content is, the stronger the hydrophobicity of humic acid is. It can be seen from the figure that the above dual-water phase distribution coefficient shows a good positive correlation with the two structural parameters.

Fig. 9 is a fitting method based on the above two-water phase partition coefficient and organic matter molecule free energy: wherein the free energy of intermolecular interaction can also be used as a parameter for characterizing the hydrophobicity of the humic acid. It can be seen from the figure that the double water phase distribution coefficients and the intermolecular interaction free energy show a good inverse relationship.

Example 3

Taking 4ml of [ C ]₄mim]Br Ionic liquid aqueous solution, 4ml40 wt% K₃PO₄And fully mixing the solution with 2ml of organic matter solution, standing for 1h at a constant temperature of 20 ℃, sampling after distribution and balance, and measuring the absorbance value of the organic matter at the position of 260nm in the upper phase and the lower phase.

At the same time, the organic matter solution was replaced with 2ml of deionized water, with 4ml of C₄mim]Br Ionic liquid aqueous solution, 4ml40 wt% K₃PO₄And fully and uniformly mixing the solution, standing at constant temperature, and sampling to determine the background absorbance value of the organic matter at 260nm in the upper phase and the lower phase.

Fig. 10 is a fitting of the two-water phase distribution coefficient and organic matter element analysis based on the above: wherein, the element ratio (O + N/C) and O/C can both represent the polarity condition of humic acid, i.e. the higher the element ratio, the stronger the polarity and the weaker the hydrophobicity. It can be seen from the figure that the above-mentioned two-aqueous phase distribution coefficients all show a good inverse relationship with the ratio of these two elements.

Fig. 11 is a fitting method based on the above two-water phase distribution coefficient and organic matter structure parameters: wherein, aromatic carbon and aromatic carbon + aliphatic carbon can both represent the hydrophobicity condition of humic acid, namely, the higher the carbon content is, the stronger the hydrophobicity of humic acid is. It can be seen from the figure that the above dual-water phase distribution coefficient shows a good positive correlation with the two structural parameters.

Fig. 12 is a fitting of the double water phase partition coefficient and the organic matter molecule free energy: wherein the free energy of intermolecular interaction can also be used as a parameter for characterizing the hydrophobicity of the humic acid. It can be seen from the figure that the double water phase distribution coefficients and the intermolecular interaction free energy show a good inverse relationship.

Example 4

Taking 2ml of [ C ]₄mim]Br Ionic liquid aqueous solution, 4ml40 wt% K₃PO₄And fully mixing the solution with 2ml of organic matter solution, standing for 1h at a constant temperature of 20 ℃, sampling after distribution and balance, and measuring the absorbance value of the organic matter at the position of 260nm in the upper phase and the lower phase.

At the same time, the organic matter solution was replaced with 2ml of deionized water, with 2ml of C₄mim]Br Ionic liquid aqueous solution, 4ml40 wt% K₃PO₄And fully and uniformly mixing the solution, standing at constant temperature, and sampling to determine the background absorbance value of the organic matter at 260nm in the upper phase and the lower phase.

Fig. 13 is a fitting of the two-water phase distribution coefficient and organic matter element analysis based on the above: wherein, the element ratio (O + N/C) and O/C can both represent the polarity condition of humic acid, i.e. the higher the element ratio, the stronger the polarity and the weaker the hydrophobicity. It can be seen from the figure that the above-mentioned two-aqueous phase distribution coefficients all show a good inverse relationship with the ratio of these two elements.

Fig. 14 is a fitting of the double water phase distribution coefficient and organic matter structure parameters: wherein, aromatic carbon and aromatic carbon + aliphatic carbon can both represent the hydrophobicity condition of humic acid, namely, the higher the carbon content is, the stronger the hydrophobicity of humic acid is. It can be seen from the figure that the above dual-water phase distribution coefficient shows a good positive correlation with the two structural parameters.

Fig. 15 is a fitting of the double water phase partition coefficient and the organic matter molecule free energy: wherein the free energy of intermolecular interaction can also be used as a parameter for characterizing the hydrophobicity of the humic acid. It can be seen from the figure that the double water phase distribution coefficients and the intermolecular interaction free energy show a good inverse relationship.

Example 5

Preparing 70% (w/w) [ C ]₄mim]And mixing the Br solution and a 50 wt% CAK (potassium citrate) solution to obtain an ionic liquid aqueous two-phase system.

Taking 4ml of [ C ]₄mim]Fully mixing Br ionic liquid aqueous solution and 4ml of 50 wt% CAK solution with 1.2ml of organic matter solution, standing for 1h in a constant temperature box at 20 ℃, and sampling to determine the absorbance value of the organic matter at 270nm in the upper phase and the lower phase after distribution and balance.

At the same time, the organic matter solution was replaced with 1.2ml of deionized water, and 4ml of [ C ]₄mim]Br Ionic liquid aqueous solution, 4ml of 40 wt% K3PO4 solutionFully and uniformly mixing, standing at constant temperature, sampling and measuring the background absorbance value of the 270nm position of the organic matter in the upper phase and the lower phase.

Fig. 16 is a fitting of the two-water phase distribution coefficient and organic matter element analysis based on the above: wherein, the element ratio (O + N/C) and O/C can both represent the polarity condition of humic acid, i.e. the higher the element ratio, the stronger the polarity and the weaker the hydrophobicity. It can be seen from the figure that the above-mentioned two-aqueous phase distribution coefficients all show a good inverse relationship with the ratio of these two elements.

Fig. 17 is a fitting of the double water phase distribution coefficient and organic matter structure parameters: wherein, aromatic carbon and aromatic carbon + aliphatic carbon can both represent the hydrophobicity condition of humic acid, namely, the higher the carbon content is, the stronger the hydrophobicity of humic acid is. It can be seen from the figure that the above dual-water phase distribution coefficient shows a good positive correlation with the two structural parameters.

Fig. 18 is a fitting of the double water phase partition coefficient and the organic matter molecule free energy: wherein the free energy of intermolecular interaction can also be used as a parameter for characterizing the hydrophobicity of the humic acid. It can be seen from the figure that the double water phase distribution coefficients and the intermolecular interaction free energy show a good inverse relationship.

Example 6

Preparing 60% (w/w) [ C ]₄mim]Br solution and 55 wt% KNaC₄H₄O₆And mixing the solutions to obtain an ionic liquid aqueous two-phase system.

Taking 4ml of [ C ]₄mim]Br Ionic liquid aqueous solution, 4ml55 wt% KNaC₄H₄O₆The solution is fully mixed with 0.5ml of organic matter solution, the mixture is kept stand for 1h in a constant temperature box at 20 ℃, and after distribution and balance, the absorbance integral value of the organic matter at the position of 255-.

At the same time, the organic matter solution was replaced with 0.5ml of deionized water, and 4ml of C₄mim]Br Ionic liquid aqueous solution, 4ml55 wt% KNaC₄H₄O₆And fully mixing the solution, standing at constant temperature, sampling and measuring the background absorbance integral value of 255-265nm organic matters in the upper phase and the lower phase.

Subtracting the background absorbance integral value to calculate the actual absorbance integral value of the upper phase and the lower phase at 255-265nm, and dividing the actual absorbance integral value of the upper phase by the actual absorbance integral value of the lower phase to obtain the distribution coefficient K of the organic matters in the double water phases_ATPS。

Fig. 19 is a fitting of the two-water phase distribution coefficient and organic matter element analysis based on the above: wherein, the element ratio (O + N/C) and O/C can both represent the polarity condition of humic acid, i.e. the higher the element ratio, the stronger the polarity and the weaker the hydrophobicity. It can be seen from the figure that the above-mentioned two-aqueous phase distribution coefficients all show a good inverse relationship with the ratio of these two elements.

Fig. 20 is a fitting of the double water phase distribution coefficient and organic matter structure parameters based on the above: wherein, aromatic carbon and aromatic carbon + aliphatic carbon can both represent the hydrophobicity condition of humic acid, namely, the higher the carbon content is, the stronger the hydrophobicity of humic acid is. It can be seen from the figure that the above dual-water phase distribution coefficient shows a good positive correlation with the two structural parameters.

Fig. 21 is a fitting of the double water phase partition coefficient and the organic matter molecule free energy: wherein the free energy of intermolecular interaction can also be used as a parameter for characterizing the hydrophobicity of the humic acid. It can be seen from the figure that the double water phase distribution coefficients and the intermolecular interaction free energy show a good inverse relationship.

The invention provides a thought and a method for applying an ionic liquid aqueous two-phase system in measuring hydrophobicity of organic matters, and a method and a way for realizing the technical scheme are many, the above description is only a preferred embodiment of the invention, and it should be noted that, for a person skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the invention, and the improvements and decorations should also be regarded as the protection scope of the invention. All the components not specified in the present embodiment can be realized by the prior art.

Claims

1. The application of the ionic liquid aqueous two-phase system in determination of organic matter hydrophobicity is characterized by comprising the following steps:

(4) correspondingly subtracting the absorbance values or absorbance integral values respectively measured by the upper phase and the lower phase in the step (2) from the background absorbance values or background absorbance integral values respectively measured by the upper phase and the lower phase in the step (3) to obtain the actual absorbance of the upper phase and the lower phase, and calculating the ratio of the actual absorbance of the upper phase to the actual absorbance of the lower phase as the distribution coefficient of the organic matter in the aqueous two phasesK _ATPS；

The organic matter is humus;

the ionic liquid aqueous two-phase system is a solution with upper and lower two-phase layering, which is formed by aqueous solution of imidazole ionic liquid and aqueous solution of inorganic salt; the volume ratio of the aqueous solution of the imidazole ionic liquid to the aqueous solution of the inorganic salt is 1 (1-2);

the imidazole ionic liquid is [ C ]₂mim]Br、[C₄mim]Br、[C₆mim]Br、[C₈mim]Br、[C₁₀mim]Br、[C₂mim]Cl、[C₄mim]Cl、[C₆mim]Cl、[C₈mim]Cl、[C₁₀mim]Any one ionic liquid of Cl;

the inorganic salt is any one of phosphate, carbonate, citrate, Rochelle salt, chloride salt, fluoride salt and acetate.

2. Use according to claim 1, wherein the organic matter is humic acid.

3. The use of claim 1, wherein the ionic liquid aqueous two-phase system is composed of [ C [ ]₄mim]The aqueous solution of Br and the aqueous solution of phosphate form a solution with upper and lower two phases separated.

4. The use as claimed in claim 1, wherein in step (2), the volume ratio of the aqueous solution of organic matter to the ionic liquid aqueous two-phase system is (0.3-2): 2-8.

5. The use according to claim 1, wherein in the step (2), the absorbance values of the upper and lower phases at a wavelength of 270nm or 260nm, or the absorbance integral values at a wavelength of 255-265nm are measured, respectively.