Application of micromolecular organic solvent-based aqueous two-phase system in determination of hydrophobicity of organic matter

Abstract

The invention discloses an application of a micromolecular organic solvent-based aqueous two-phase system in determination of hydrophobicity of organic matters, and relates to the technical field of organic matter determination, and the micromolecular organic solvent-based aqueous two-phase system is a solution which is formed by a micromolecular organic solvent aqueous solution and an inorganic salt aqueous solution and has an upper phase and a lower phase which are layered. According to the method, the high-throughput detection of the hydrophobicity of the organic matter sample can be realized by measuring the absorbance of the upper phase and the lower phase by utilizing a small-molecule organic solvent-based aqueous two-phase system.

Description

TECHNICAL FIELD

[0001] The application relates to application of a small-molecule organic solvent-based aqueous two-phase system to determination of hydrophobicity of organic matter and belongs to the technical field of determination of organic matter. BACKGROUND

[0002] Hydrophobicity, as one of important properties of dissolved organic matter (DOM), has important environmental significance for many geochemical and engineering water treatment processes. Hydrophobicity affects the distribution of organic pollutants on DOM, transport, fate and bioavailability in the environment.

[0003] From the DOM itself, hydrophobicity affects the aggregation behavior of the DOM itself and plays an important role in the carbon cycle. In engineering applications, hydrophobicity affects membrane fouling and the formation of disinfection by-products in water treatment processes. Therefore, for both laboratory and field applications, it is important to quickly and real-time monitor this important property.

[0004] The methods for quantifying the hydrophobicity of DOM in the literature mainly include resin fractionation, elemental analysis, nuclear magnetic resonance spectroscopy (NMR), spectroscopy and reversed-phase high-performance liquid chromatography (RP-HPLC). However, resin fractionation, elemental analysis, nuclear magnetic resonance spectroscopy and reversed-phase high-performance liquid chromatography are limited by complex operation processes or large instruments, are limited to laboratory determination, cannot realize high-throughput determination and lack potential for field application. Although spectroscopy has a certain field operability, the method is an indirect characterization method for DOM hydrophobicity, and the results lack accuracy. SUMMARY

[0005] The application aims to overcome the deficiencies in the prior art and provide application of a small-molecule organic solvent-based aqueous two-phase system to determination of hydrophobicity of organic matter. The small-molecule organic solvent-based aqueous two-phase system can realize high-throughput detection of organic matter samples by determining the absorbance of the upper and lower phases.

[0006] To achieve the above-mentioned purpose, the application is implemented by using the following technical scheme: On one hand, the application provides application of a small-molecule organic solvent-based aqueous two-phase system to determination of hydrophobicity of organic matter.

[0007] Further, the small-molecule organic solvent-based aqueous two-phase system is a solution with upper and lower phase stratification formed by a small-molecule organic solvent aqueous solution and an inorganic salt aqueous solution.

[0008] Further, the small-molecule organic solvent aqueous solution is one of methanol, ethanol, 2-propanol, acetonitrile and propylamine.

[0009] Further, the inorganic salt aqueous solution is one of a sulfate, a carbonate, a phosphate and a citrate.

[0010] Further, the mass fraction of the small-molecule organic solvent aqueous solution and the inorganic salt aqueous solution both satisfy being above the double-node line of the phase diagram of the small-molecule organic solvent aqueous solution and the inorganic salt aqueous solution.

[0011] Further, the mass fraction of the small-molecule organic solvent aqueous solution is 15-30 wt%, and the mass fraction of the inorganic salt aqueous solution is 35-45 wt%.

[0012] Further, the organic matter includes natural source humus and artificial source organic matter.

[0013] Further, the natural source humus is humic acid, and the artificial source organic matter is dissolved black carbon.

[0014] In another aspect, the application further provides a method for using the small-molecule organic solvent-based aqueous two-phase system in measuring the hydrophobicity of organic matter, comprising: adding an aqueous solution of the organic matter to be detected into the small-molecule organic solvent-based aqueous two-phase system as claimed in any one of claims 1-8, mixing thoroughly, and standing until the system forms an upper and lower two-phase layered solution, and then measuring the absorbance values of the upper and lower two phases respectively; taking the same volume of deionized water as the aqueous solution of the organic matter to be detected, adding the deionized water into the small-molecule organic solvent-based aqueous two-phase system, mixing thoroughly, and standing until the system forms an upper and lower two-phase layered solution, and then measuring the background absorbance values of the upper and lower two phases respectively; subtracting the background absorbance values of the upper and lower two phases from the absorbance values of the upper and lower two phases respectively to obtain the actual absorbance values of the upper and lower two phases; taking the ratio of the actual absorbance value of the upper phase to the actual absorbance value of the lower phase as the partition coefficient of the organic matter in the two phases, and the partition coefficient is used to characterize the hydrophobicity of the organic matter to be detected.

[0015] Further, the absorbance values and the background absorbance values are measured at the same wavelength, and the wavelength range is 250-350 nm.

[0016] Compared with the prior art, the application has the following beneficial effects: The small-molecule organic solvent-based aqueous two-phase system is used to realize high-throughput detection of the organic matter sample by measuring the absorbance values of the upper and lower two phases, and the rapid phase separation promotes the detection speed, and the centrifugation operation is not needed, and the complex instrument is not needed, and the application has the advantages of being fast, simple, low-cost and environment-friendly, and lays a foundation for realizing high-throughput detection and potential automation of the hydrophobicity of the organic matter. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1A phase diagram of different kinds of small-molecule organic solvent solutions and different salt solutions in an embodiment of the present application; Figure 2 A schematic diagram of partition kinetics of an ethanol / sodium sulfate aqueous two-phase system in Example 1 of the present application; Figure 3 A partition coefficient of a dissolved black carbon sample in an ethanol / sodium sulfate aqueous two-phase system in Example 1 of the present application K ATPS A fitting result diagram of element ratios of a dissolved black carbon sample, wherein (a) is a fitting result diagram of an element ratio (O + N) / C of a dissolved black carbon sample, and (b) is a fitting result diagram of an element ratio O / C of a dissolved black carbon sample.

[0018] Figure 4 A partition coefficient of a dissolved black carbon sample in a propylamine / potassium carbonate aqueous two-phase system in Example 2 of the present application K ATPS A fitting result diagram of element ratios of a dissolved black carbon sample, wherein (a) is a fitting result diagram of an element ratio (O + N) / C of a dissolved black carbon sample, and (b) is a fitting result diagram of an element ratio O / C of a dissolved black carbon sample. Figure 5 A partition coefficient of a dissolved black carbon sample in an acetonitrile / sodium sulfate aqueous two-phase system in Example 3 of the present application K ATPS A fitting result diagram of element ratios of a dissolved black carbon sample, wherein (a) is a fitting result diagram of an element ratio (O + N) / C of a dissolved black carbon sample, and (b) is a fitting result diagram of an element ratio O / C of a dissolved black carbon sample. DETAILED DESCRIPTION

[0019] The present application will be further described below in conjunction with the accompanying drawings. The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application. Example 1

[0020] The present application provides an application of a small-molecule organic solvent-based aqueous two-phase system in determining hydrophobicity of organic matter, which specifically comprises the following steps: Prepare a small-molecule organic solvent-based aqueous two-phase system, in the present embodiment, 15 wt% ethanol aqueous solution is used as the upper phase, and 35 wt% sodium sulfate aqueous solution is used as the lower phase, to obtain an ethanol / sodium sulfate aqueous two-phase system.

[0021] The partition kinetics of the ethanol / sodium sulfate aqueous two-phase system is shown in Figure 2 The partition equilibrium of the organic matter can be achieved within 10 minutes, which indicates that the system can meet the high-throughput requirement.

[0022] It is noted that, as shown in Figure 1 Figure 1 is a phase diagram of an ethanol solution and an inorganic salt solution, and the phase diagram (binodal line) of the ethanol solution and different inorganic salt solutions is determined by a cloud point titration method, and specifically includes the following steps: At room temperature, a certain amount of inorganic salt solution is weighed and placed in a 15 mL centrifuge tube.

[0023] The ethanol aqueous solution is added to the 15 mL centrifuge tube while stirring until turbidity appears, and the addition is stopped to obtain a mixture. The same operation is performed for different types of inorganic salt solutions. The composition of the mixture is calculated to obtain a binodal point on the binodal line. Then, a small amount of water is added to the mixture until the turbidity disappears and grows, and the above operation is repeated to obtain multiple binodal points, which form the binodal line.

[0024] The area above the binodal line is the concentration ratio of two phases that meet the phase separation condition, and the area below the binodal line is the concentration ratio of two phases that do not meet the phase separation condition (the area above the binodal line does not meet the high-throughput determination requirement).

[0025] In the embodiment of the present application, the organic matter to be measured is selected as a dissolved black carbon sample, and the preparation method of the dissolved black carbon sample is as follows: corn, peanut, rice, sorghum, and rape are used as raw materials, the temperature of the muffle furnace is set to increase from 20℃ to 400℃ at a rate of 5℃ / min, and the temperature is maintained for 3 h, and the pyrolysis is performed to obtain biochar. Then, the biochar is ground and passed through a 100 mesh sieve to obtain 5 kinds of biochar powders.

[0026] Then, corn straw is used as a raw material, the temperature of the muffle furnace is set to increase from 20℃ to 400℃ at a rate of 5℃ / min, and the temperature is maintained for 4 h, and the pyrolysis is performed to obtain biochar. Then, the biochar is ground and passed through a 100 mesh sieve to obtain the 6th kind of biochar powder.

[0027] Corn straw is used as a raw material, the temperature of the muffle furnace is set to increase from 20℃ to 400℃ at a rate of 5℃ / min, and the temperature is maintained for 6 h, and the pyrolysis is performed to obtain biochar. Then, the biochar is ground and passed through a 100 mesh sieve to obtain the 7th kind of biochar powder.

[0028] Corn straw is used as a raw material, the temperature of the muffle furnace is set to increase from 20℃ to 400℃ at a rate of 5℃ / min, and the temperature is maintained for 8 h, and the pyrolysis is performed to obtain biochar. Then, the biochar is ground and passed through a 100 mesh sieve to obtain the 8th kind of biochar powder.

[0029] ​The corn stalks were used as raw material, and the temperature of the muffle furnace was set to increase from 20 °C to 400 °C at a rate of 1.5 °C / min, and kept at this temperature for 3 h, and the pyrolysis obtained biochar. Subsequently, the biochar was ground and passed through a 100 mesh screen to obtain 9 kinds of biochar powder.

[0030] The temperature of the muffle furnace was set to increase from 20 °C to 400 °C at a rate of 1 °C / min, and kept at this temperature for 3 h, and the pyrolysis obtained biochar. Subsequently, the biochar was ground and passed through a 100 mesh screen to obtain the 10th biochar powder.

[0031] The temperature of the muffle furnace was set to increase from 20 °C to 500 °C at a rate of 5 °C / min, and kept at this temperature for 3 h, and the pyrolysis obtained biochar. Subsequently, the biochar was ground and passed through a 100 mesh screen to obtain the 11th biochar powder.

[0032] The temperature of the muffle furnace was set to increase from 20 °C to 600 °C at a rate of 5 °C / min, and kept at this temperature for 3 h, and the pyrolysis obtained biochar. Subsequently, the biochar was ground and passed through a 100 mesh screen to obtain the 12th biochar powder.

[0033] The above-mentioned 12 kinds of biochar powder were obtained by water extraction method to obtain dissolved black carbon samples, specifically including: taking 50 g of biochar powder dispersed in 800 mL of deionized water, stirring and then ultrasonic treatment in a water bath ultrasonic instrument at a power of 100 W for 30 min. The suspension was filtered with a 0.45 μm filter membrane (Supor-450, Pall, USA), and the obtained filtrate was the dissolved black carbon sample. The pH of the dissolved black carbon sample was adjusted to 6.9 ± 0.1, and the concentration of the dissolved black carbon sample was determined by TOC. The dissolved black carbon sample was stored in a 4 °C refrigerator in the dark before the experiment.

[0034] The following uses 12 kinds of dissolved black carbon samples to determine the hydrophobicity of organic matter, and the specific steps are as follows: take 2 mL of ethanol aqueous solution, 1.5 mL of sodium sulfate aqueous solution and 0.75 mL of dissolved black carbon solution, mix thoroughly, stand for 1 h, and then take samples to determine the absorbance value of the dissolved black carbon solution at 270 nm in the upper and lower phases after equilibrium.

[0035] Then, the dissolved black carbon solution is replaced with 0.75 mL of deionized water, mixed thoroughly with 2 mL of ethanol aqueous solution and 1.5 mL of sodium sulfate aqueous solution, and then samples are taken to determine the background absorbance value of the dissolved black carbon solution at 270 nm in the upper and lower phases after constant temperature standing.

[0036] The actual absorbance of the upper and lower phases is calculated by subtracting the background absorbance value from the absorbance value, and the partition coefficient of the dissolved black carbon solution in the aqueous two-phase system is obtained by dividing the actual absorbance of the upper phase by the actual absorbance of the lower phase. K ATPS .

[0037] The fitting results of the distribution coefficients of 12 dissolved black carbon samples in the ethanol / sodium sulfate aqueous two-phase system and the element ratios (O + N) / C and O / C of the corresponding dissolved black carbon samples are shown in Figure 3 As shown in the table, the element ratio is the element content ratio determined by the element analyzer, and the element ratios (O + N) / C and O / C both represent the polarity of the dissolved black carbon, that is, the higher the element ratio, the stronger the polarity, and the stronger the hydrophilicity. Therefore, the element ratios (O + N) / C and O / C can be used to characterize the hydrophilicity of the substance, and the stronger the hydrophilicity, the weaker the hydrophobicity.

[0038] As can be seen from Figure 3 , the distribution coefficients based on the above ethanol / sodium sulfate aqueous two-phase system and the element ratios (O + N) / C and O / C both show a good inverse relationship, indicating that the ethanol / sodium sulfate aqueous two-phase system in this embodiment can better characterize the hydrophobicity of organic matter. Example 2

[0039] This embodiment provides an application of a small-molecule organic solvent-based aqueous two-phase system in determining the hydrophobicity of organic matter. The difference from Example 1 is only that the upper phase of the small-molecule organic solvent-based aqueous two-phase system in this embodiment uses 15wt% propylamine aqueous solution, and the lower phase uses 30wt% potassium carbonate aqueous solution, obtaining a propylamine / potassium carbonate aqueous two-phase system.

[0040] The fitting results of the distribution coefficients of dissolved black carbon in the propylamine / potassium carbonate aqueous two-phase system and the element ratios (O + N) / C and O / C are shown in Figure 4 As can be seen from Figure 4 , the distribution coefficients based on the above propylamine / potassium carbonate aqueous two-phase system and the element ratios (O + N) / C and O / C both show a good inverse relationship, indicating that the propylamine / potassium carbonate aqueous two-phase system in this embodiment can better characterize the hydrophobicity of organic matter. Example 3

[0041] This embodiment provides an application of a small-molecule organic solvent-based aqueous two-phase system in determining the hydrophobicity of organic matter. The difference from Example 1 is only that the upper phase of the small-molecule organic solvent-based aqueous two-phase system in this embodiment uses 50wt% acetonitrile aqueous solution, and the lower phase uses 40wt% sodium sulfate aqueous solution, obtaining an acetonitrile / sodium sulfate aqueous two-phase system.

[0042] The fitting results of the distribution coefficients of dissolved black carbon in the acetonitrile / sodium sulfate aqueous two-phase system and the element ratios (O + N) / C and O / C are shown in Figure 5 As can be seen from Figure 5It can be seen that the distribution coefficient based on the above acetonitrile / sodium sulfate aqueous two-phase system and the element ratio (O + N) / C, O / C all present a good inverse relationship, which shows that the acetonitrile / sodium sulfate aqueous two-phase system in the embodiment can better characterize the hydrophobicity of organic matter.

[0043] The "n-octanol-water system" is an extremely important model system in the fields of chemistry, pharmacy, environmental science, etc., and is mainly used for studying the hydrophobicity / lipophilicity of substances. Although n-octanol is a small-molecule organic solvent, n-octanol and water are partially miscible liquids at room temperature (about 25°C), and the solubility of n-octanol in water is very low, about 0.05-0.10 mol% (about 0.008%-0.015% by weight). This means that the saturated aqueous phase contains only a trace amount of n-octanol, and therefore the two-phase system formed by n-octanol and water is not miscible, which is caused by the extremely low solubility, and is essentially different from the aqueous two-phase system mentioned in the present patent.

[0044] The aqueous two-phase system involved in the present patent is a system formed by two water-soluble solvents that are not miscible with each other at a specific concentration, and the phase separation mainly occurs due to salting-out and the like. Further experimental verification found that organic matter does not spontaneously distribute in the n-octanol-water system, and all the organic matter is enriched in the aqueous phase. This phenomenon shows that not all two-phase systems containing small-molecule organic solvents are suitable for the determination of the hydrophobicity of organic matter.

[0045] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. Application of small molecule organic solvent-based aqueous two-phase system in determining the hydrophobicity of organic matter.

2. The use of the small molecule organic solvent-based aqueous two-phase system according to claim 1 in determining the hydrophobicity of organic matter, characterized in that: The small molecule organic solvent-based aqueous two-phase system is a solution with upper and lower phases formed by a small molecule organic solvent aqueous solution and an inorganic salt aqueous solution.

3. The use of the small molecule organic solvent-based aqueous two-phase system according to claim 2 in determining the hydrophobicity of organic matter, characterized in that: The small molecule organic solvent aqueous solution is one of methanol, ethanol, 2-propanol, acetonitrile and propylamine.

4. The use of the small molecule organic solvent-based aqueous two-phase system according to claim 2 in determining the hydrophobicity of organic matter, characterized in that: The inorganic salt aqueous solution is one of sulfate, phosphate, carbonate and citrate.

5. The use of the small molecule organic solvent-based aqueous two-phase system according to claim 2 in determining the hydrophobicity of organic matter, characterized in that: The mass fractions of the small molecule organic solvent aqueous solution and the inorganic salt aqueous solution both satisfy the requirement of being located above the binodal line of the phase separation diagram of the small molecule organic solvent aqueous solution and the inorganic salt aqueous solution.

6. Use of the small molecule organic solvent-based aqueous two-phase system according to claim 5 in determining the hydrophobicity of organic matter, characterized in that: The mass fraction of the small molecule organic solvent aqueous solution is 15-30 wt %, and the mass fraction of the inorganic salt aqueous solution is 35-45 wt %.

7. Use of the small molecule organic solvent-based aqueous two-phase system according to claim 1 in determining the hydrophobicity of organic matter, characterized in that: The organic matter includes humus of natural origin and organic matter of artificial origin.

8. Use of the small molecule organic solvent-based aqueous two-phase system according to claim 7 in determining the hydrophobicity of organic matter, characterized in that: The natural humus is humic acid, and the artificial organic matter is dissolved black carbon.

9. A method for using a small molecule organic solvent-based aqueous two-phase system in determining the hydrophobicity of organic matter, characterized in that: include: Add the organic matter aqueous solution to be tested into the small molecule organic solvent-based aqueous two-phase system according to any one of claims 1 to 8 and mix thoroughly, let the system stand until the upper and lower phases are formed, and measure the absorbance values ​​of the upper and lower phases respectively; Take deionized water of the same volume as the aqueous solution of the organic matter to be detected, add it to the small molecule organic solvent-based aqueous two-phase system and mix thoroughly. Let it stand until the system forms upper and lower phases, and measure the background absorbance values ​​of the upper and lower phases respectively; The absorbance values ​​of the upper and lower phases are subtracted from the background absorbance values ​​of the upper and lower phases to obtain the actual absorbance of the upper and lower phases; The ratio of the actual absorbance of the upper phase to the actual absorbance of the lower phase is used as the partition coefficient of the organic matter in the two phases, and the partition coefficient is used to characterize the hydrophobicity of the organic matter to be detected.

10. The method for using the small molecule organic solvent-based aqueous two-phase system in determining the hydrophobicity of organic matter according to claim 9, characterized in that: The absorbance value and the background absorbance value are measured at the same wavelength, and the wavelength range is 250-350 nm.

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