Measurement Method of Chiral Distribution of Chemical Root Inhibitors

Abstract

The present application discloses a method for measuring the chiral distribution of a chemical root inhibitor. A method for measuring the chiral distribution of a chemical root inhibitor comprises: performing a saponification reaction on the chemical root inhibitor to convert the active substance in the chemical root inhibitor into 2-methyl-4-chlorophenoxypropionic acid; purifying the 2-methyl-4-chlorophenoxypropionic acid using an eluent and dissolving it in a solvent to obtain a refined 2-methyl-4-chlorophenoxypropionic acid solution; obtaining relationship data between the optical rotation and optical purity of multiple sample liquids, and fitting the relationship data to obtain a standard curve, wherein the multiple sample liquids include sample liquids with an optical purity of 95% and 0%; measuring the optical rotation of the refined 2-methyl-4-chlorophenoxypropionic acid solution to obtain a measured optical rotation; determining the chiral distribution of the chemical root inhibitor based on the measured optical rotation and the standard curve. According to an embodiment of the present application, the chiral distribution of the chemical root inhibitor can be measured at low cost, quickly and accurately.

Description

Technical Field

[0001] The present application belongs to the field of asphalt coil additives, and in particular relates to a method for measuring the chiral distribution of chemical root inhibitors. Background Art

[0002] The most common chiral distribution test uses a high-performance liquid chromatography (HPLC) chiral column to separate different configurations and then calculate the distribution. This can be divided into chiral derivatization, chiral mobile phase, and chiral stationary phase methods.

[0003] Although this test method is relatively mature, due to the wide variety of root inhibitors, especially polymer-type root inhibitors, which have complex structures, there are certain difficulties in directly using chiral columns for chiral separation. There are also problems such as high testing costs and long testing time. Summary of the Invention

[0004] The embodiment of the present application provides a method for measuring the chiral distribution of a chemical root inhibitor, which can measure the chiral distribution of a chemical root inhibitor quickly and accurately at low cost.

[0005] An embodiment of the present application provides a method for measuring the chiral distribution of a chemical root inhibitor, comprising: performing a saponification reaction on the chemical root inhibitor to convert the active substance in the chemical root inhibitor into 2-methyl-4-chlorophenoxypropionic acid; purifying the 2-methyl-4-chlorophenoxypropionic acid using an eluent and dissolving it in a solvent to obtain a refined 2-methyl-4-chlorophenoxypropionic acid solution; obtaining relationship data between the optical rotation and optical purity of multiple sample liquids, and fitting the relationship data to obtain a standard curve, the multiple sample liquids including sample liquids with optical purity of 95% and 0%; measuring the optical rotation of the refined 2-methyl-4-chlorophenoxypropionic acid solution to obtain a measured optical rotation; and measuring the optical purity of the refined 2-methyl-4-chlorophenoxypropionic acid solution based on the measured optical rotation and the standard curve to determine the chiral distribution of the chemical root inhibitor.

[0006] In any embodiment of the present application, the step of saponifying the chemical root inhibitor includes: mixing materials containing the chemical root inhibitor, an organic solvent and an alkali solution under preset conditions to obtain a mixed liquid; subjecting the mixed liquid to rotary evaporation to remove the organic solvent to obtain an aqueous solution; adding an extractant to the aqueous solution to obtain an upper aqueous phase; adjusting the pH of the upper aqueous phase to 5.8-6.2, and then adding an extractant to obtain a lower organic phase, which is subjected to rotary evaporation and drying to obtain 2-methyl-4-chlorophenoxypropionic acid.

[0007] In any embodiment of the present application, in the step of mixing the materials containing the chemical root inhibitor, the organic solvent and the alkali solution under preset conditions, the ratio of the mass of the chemical root inhibitor to the volume of the organic solvent and the volume of the alkali solution is 1:15~25:15~25.

[0008] In any embodiment of the present application, in the step of mixing the materials containing the chemical root inhibitor, the organic solvent and the alkali solution under preset conditions, the concentration of the alkali solution is 0.1 to 0.5 g / mL.

[0009] In any embodiment of the present application, the step of adjusting the pH of the upper aqueous phase to 5.8-6.2 includes: adding an acid solution of a preset concentration to the upper aqueous phase to adjust the pH to 5.8-6.2.

[0010] In any embodiment of the present application, the step of adjusting the pH of the upper aqueous phase to 5.8-6.2 includes: performing column separation on the upper aqueous phase to adjust the pH to 5.8-6.2.

[0011] In any embodiment of the present application, in the step of purifying 2-methyl-4-chlorophenoxypropionic acid with an eluent and dissolving it in a solvent, the eluent includes at least one of dichloromethane and methanol.

[0012] In any embodiment of the present application, in the purified 2-methyl-4-chlorophenoxypropionic acid solution and the plurality of sample solutions, the solvent comprises at least one of dichloromethane, toluene, chloroform and petroleum ether.

[0013] In any embodiment of the present application, the concentrations of the purified 2-methyl-4-chlorophenoxypropionic acid solution and the multiple sample solutions are all 0.1 to 0.3 g / mL.

[0014] In any embodiment of the present application, the correlation coefficient of the standard curve is 0.99 to 0.999.

[0015] The method for measuring the chiral distribution of chemical root inhibitors in the embodiment of the present application can solve the problem of difficulty in separating chirality using a chiral column, and can measure the chiral distribution of chemical root inhibitors quickly and at low cost; at the same time, the purified 2-methyl-4-chlorophenoxypropionic acid can reduce the optical rotation difference caused by impurities, reduce interference factors, and improve measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0017] Figure 1 This is the standard curve in Example 1 of the present application. DETAILED DESCRIPTION

[0018] In order to more clearly understand the above-mentioned objectives, features and advantages of the present application, the scheme of the present application will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present application may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present application, rather than all of the embodiments.

[0020] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0021] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0022] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0023] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0024] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0025] Unless otherwise specified, this application adopts conventional test methods or test methods recommended by the instrument.

[0026] In this application, the optical rotation test instrument model is WZZ-2S automatic polarimeter.

[0027] Among the most common chemical root inhibitors currently used, 2-methyl-4-chlorophenoxypropionate is the active compound. Common products include 2-methyl-4-chlorophenoxypropionate isooctyl ester and 2-methyl-4-chlorophenoxypropionate polyethylene glycol ester. After addition to asphalt membranes, under natural conditions, the ester bonds in the chemical root inhibitor slowly break down, producing 2-methyl-4-chlorophenoxypropionic acid (MCPP acid), which has a certain degree of biotoxicity and inhibits plant root growth. The chemical activity of MCPP acid can vary by more than ten times depending on its chiral configuration. Therefore, determining the chiral distribution of chemical root inhibitors is crucial for evaluating their performance. The more active MCPP acid is the R configuration, whose structural formula is shown below. Research has shown that it exhibits optical rotation.

[0028]

[0029] This application converts 2-methyl-4-chlorophenoxypropionate in the analyte into MCPP acid through a saponification reaction, then measures the optical rotation of the MCPP acid using a polarimeter, and then substitutes the optical rotation into a standard curve for optical rotation and optical purity to obtain the optical purity of the MCPP acid obtained by converting 2-methyl-4-chlorophenoxypropionate in the analyte, thereby obtaining the chiral distribution of the analyte (chemical root inhibitor). The standard curve for optical rotation and optical purity is established using several groups of MCPP acids with known optical purity and optical rotation. In particular, for polymer-based root inhibitors with relatively complex structures, this method can solve the problem of difficulty in chiral separation using chiral columns. Moreover, this test method has the advantages of being fast, versatile, low in testing cost, and short in testing time. At the same time, by purifying the MCPP acid, this application can reduce the optical rotation differences caused by impurities, reduce interfering factors, and make the measurement results more accurate. The test method provided in this application has low requirements for instruments and operators, and also has low requirements for solvents. Different solvents such as dichloromethane, toluene, methanol, ethanol, DMF, etc. can be used. After equipping a visual polarimeter in the factory, on-site testing can be carried out using analytical grade or industrial grade solvents. After the values ​​are obtained, they can be filled in the corresponding table to obtain the results. The chiral distribution of MCPP acid and chemical root inhibitors can be quickly and cost-effectively determined.

[0030]

Measurement method

[0031] An embodiment of the present application provides a method for measuring the chiral distribution of a chemical root inhibitor, comprising: performing a saponification reaction on the chemical root inhibitor to convert the active substance in the chemical root inhibitor into 2-methyl-4-chlorophenoxypropionic acid; purifying the 2-methyl-4-chlorophenoxypropionic acid using an eluent and dissolving it in a solvent to obtain a refined 2-methyl-4-chlorophenoxypropionic acid solution; obtaining relationship data between the optical rotation and optical purity of multiple sample liquids, and fitting the relationship data to obtain a standard curve, the multiple sample liquids including sample liquids with optical purity of 95% and 0%; measuring the optical rotation of the refined 2-methyl-4-chlorophenoxypropionic acid solution to obtain a measured optical rotation; and measuring the optical purity of the refined 2-methyl-4-chlorophenoxypropionic acid solution based on the measured optical rotation and the standard curve to determine the chiral distribution of the chemical root inhibitor.

[0032] A standard curve is a graph formed by measuring the values ​​of a specific physical or chemical property of a series of standard substances of known composition. The standard curve represents the functional relationship between the physical / chemical properties of the standard substance and the instrument response. This is a method of empirical coefficients that represents the matrix effect of one element on another. Even without mathematical proof, it is intuitively understood that the spectral line intensity of element i in the matrix and the concentrations of the other coexisting elements have a single-valued functional relationship. This single-valued functional relationship is derived by solving a matrix using several sets of standard samples with the same matrix composition (elements or element oxides, but varying concentrations) and known concentrations of each component (calculated using a computer program). Optical purity, also known as optical rotation purity, is the percentage of a compound's specific optical rotation relative to the pure substance. The present application converts 2-methyl-4-chlorophenoxypropionate in a chemical root inhibitor into MCPP acid through a saponification reaction, measures the optical rotation of the MCPP acid using a polarimeter, and then obtains the optical purity corresponding to the MCPP acid by using a functional relationship between the optical rotation and optical purity revealed by a standard curve established using a standard substance (sample), thereby obtaining the optical purity of the chemical root inhibitor.

[0033] In some embodiments, the step of subjecting the chemical root inhibitor to a saponification reaction includes: mixing materials containing the chemical root inhibitor, an organic solvent, and an alkaline solution under predetermined conditions to obtain a mixed solution; subjecting the mixed solution to rotary evaporation to remove the organic solvent to obtain an aqueous solution; adding an extractant to the aqueous solution to obtain an upper aqueous phase; adjusting the pH of the upper aqueous phase to 5.8 to 6.2, and then adding an extractant to obtain a lower organic phase, which is subjected to rotary evaporation and drying to obtain 2-methyl-4-chlorophenoxypropionic acid. The active substance in the chemical root inhibitor is converted into 2-methyl-4-chlorophenoxypropionic acid through the saponification reaction, thereby facilitating the accurate determination of the chiral distribution of the chemical root inhibitor.

[0034] In some embodiments, during the step of mixing the materials containing the chemical root inhibitor, the organic solvent, and the alkali solution under predetermined conditions, the ratio of the mass of the chemical root inhibitor to the volume of the organic solvent to the volume of the alkali solution is 1:15-25:15-25. This ratio can shorten the reaction time and increase the yield of 2-methyl-4-chlorophenoxypropionic acid.

[0035] In some embodiments, during the step of mixing the materials containing the chemical root inhibitor, the organic solvent, and the alkali solution under predetermined conditions, the concentration of the alkali solution is 0.1 to 0.5 g / mL. Within this range, the reaction time can be shortened and the yield of 2-methyl-4-chlorophenoxypropionic acid can be increased.

[0036] In some embodiments, the step of adjusting the pH of the upper aqueous phase to 5.8-6.2 includes adding an acid solution of a preset concentration to the upper aqueous phase to adjust the pH to 5.8-6.2.

[0037] The predetermined concentration of the strong acid solution is not particularly limited and can be adjusted by those skilled in the art as needed. As an example, 125 mmol of concentrated hydrochloric acid can be added to the upper aqueous phase to adjust the pH to 5.8-6.2.

[0038] In some embodiments, the step of adjusting the pH of the upper aqueous phase to 5.8-6.2 includes: subjecting the upper aqueous phase to column separation treatment and adjusting the pH to 5.8-6.2.

[0039] The conditions for column separation are not particularly limited and can be adjusted as needed by those skilled in the art. As an example, an ion exchange column can be used. As another example, an adsorption column can be used.

[0040] In some embodiments, in the step of purifying the 2-methyl-4-chlorophenoxypropionic acid using an eluent and dissolving it in a solvent, the eluent includes at least one of dichloromethane and methanol. During the purification of the 2-methyl-4-chlorophenoxypropionic acid, the crude product is purified by column chromatography using a 200-mesh silica gel column. Impurities are initially eluted with dichloromethane, and later with a 20 / 1 dichloromethane / methanol mixture to elute the MCPP acid. The purified MCPP acid is then dried under vacuum by rotary evaporation.

[0041] In some embodiments, the solvent in the refined 2-methyl-4-chlorophenoxypropionic acid solution and the plurality of sample solutions comprises at least one of dichloromethane, toluene, chloroform, and petroleum ether.

[0042] In some embodiments, the concentration of the refined 2-methyl-4-chlorophenoxypropionic acid solution and the multiple sample liquids is 0.1 to 0.15 g / mL. Alternatively, the concentration of the refined 2-methyl-4-chlorophenoxypropionic acid solution and the multiple sample liquids is 0.1 to 0.3 g / mL. Within this range, the accuracy and reliability of the measurement results can be ensured. This is because when the concentration of the test product (refined 2-methyl-4-chlorophenoxypropionic acid solution) and the standard (multiple sample liquids) is higher than the linear range, the signal is saturated and it is difficult to obtain reliable data.

[0043] In some embodiments, the correlation coefficient of the standard curve is 0.99 to 0.999. Alternatively, the correlation coefficient of the standard curve is 0.99 to 0.9999.

[0044] Example 1

[0045] Step 1, saponification reaction:

[0046] 10 g of a chemical root inhibitor sample (purchased from Codow CD17767) was dissolved in 200 mL of ethanol to obtain a solution containing the chemical root inhibitor. 5 g of NaOH was dissolved in 200 mL of water to obtain a NaOH solution. The two were mixed and ultrasonicated at 40°C for 1 h, and then cooled to room temperature to obtain a mixed solution.

[0047] The mixture was rotary evaporated at 40 °C for 1 h to remove ethanol and obtain an aqueous solution;

[0048] Add 200 ml of dichloromethane to the above aqueous solution, separate the liquids and take the upper aqueous phase;

[0049] 12.3 g of concentrated hydrochloric acid was added to the aqueous phase to adjust the pH to 6, and then 200 ml of dichloromethane was added. After separation, the lower organic phase was taken, the solvent was dried at room temperature, and vacuum dried to obtain a white or light yellow solid, which was the crude MCPP acid.

[0050] Step 2: Purification:

[0051] The crude MCPP acid was purified by column chromatography using a 200-mesh silica gel column. Dichloromethane was initially used to elute impurities, and later a dichloromethane / methanol = 20 / 1 mixed solvent was used to elute the MCPP acid. The purified MCPP acid was then dried under vacuum by rotary evaporation to obtain the purified MCPP acid.

[0052] Step 3: Draw the standard curve:

[0053] Chiral and achiral MCPP acid standards were obtained, with optical purities (ee values) of 95% and 0%, respectively; during the measurement, the optical rotation tube was fixed in position and orientation;

[0054] Use a 25mL volumetric flask to prepare a dichloromethane solution with a concentration of 0.1g / mL;

[0055] 2.5 g of the purified MCPP acid was weighed into a 50 mL beaker and dissolved in 8 mL of dichloromethane. After dissolution, the solution was transferred to a volumetric flask. The residue in the beaker was rinsed three times with a small amount of dichloromethane. The volume was then brought to the mark and mixed thoroughly to obtain a 0.1 g / mL dichloromethane solution containing purified MCPP acid, designated as the experimental group. Using the same method, a 95% optically pure MCPP acid standard solution (sample solution) and a 0% optically pure MCPP acid standard solution were prepared. 4 mL of the 0% standard solution and 6 mL of the 95% standard solution were mixed to obtain a 57% optically pure standard solution. 6 mL of the 0% standard solution and 4 mL of the 95% standard solution were mixed to obtain a 38% optically pure standard solution.

[0056] Use an automatic polarimeter to measure the optical rotation of the four standard solutions and the experimental group, and take the average value of the four measurements. With the optical rotation of the standard solution as the x-axis and the ee value as the y-axis, the standard curve equation of optical rotation-ee value is obtained by fitting. The results are as follows Figure 1 As shown, y = 0.03308x - 0.03878.

[0057] Step 4: Chiral distribution test:

[0058] Substituting the measured optical rotation of the experimental group into the above equation, the corresponding ee value calculated was 93.5%, which is the chiral distribution of the chemical root inhibitor.

[0059] Example 2

[0060] The implementation steps are the same as those of implementation 1, except that only the amount of NaOH in step 1 is changed to 20 g, and the ee value of the obtained chemical root inhibitor is 93.9%.

[0061] Example 3

[0062] The implementation steps are the same as those of implementation 1, except that only the solvent in step 2 is changed to chloroform, and the ee value of the obtained chemical root inhibitor is 92.7%.

[0063] Example 4

[0064] The implementation steps are the same as those of implementation 1, except that only the solvent in step 3 is changed to chloroform, and the ee value of the obtained chemical root inhibitor is 93.1%.

[0065] Comparative Example 1

[0066] The experimental steps were the same as those in Example 1, except that only step 2 was omitted. The ee value of the obtained chemical root inhibitor was 95.3%.

[0067] It can be seen from Comparative Example 1 and Example 1 that the purified 2-methyl-4-chlorophenoxypropionic acid can reduce the difference in optical rotation caused by impurities, reduce interference factors, and improve measurement accuracy.

[0068] In addition, compared with the chiral column testing method in the related art, the embodiment of the present application has the advantages of low cost, short testing time and strong broad spectrum.

[0069] The above description is only a specific embodiment of the present application. Those skilled in the art will clearly understand that for the convenience and brevity of description, the specific working processes of the systems, modules and units described above can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here. It should be understood that the scope of protection of the present application is not limited thereto. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the scope of protection of the present application.

Claims

1. A method for measuring the chiral distribution of a chemical root inhibitor, characterized in that: include: A saponification reaction is performed on a chemical root inhibitor containing 2-methyl-4-chlorophenoxypropionate to convert the active substance in the chemical root inhibitor into 2-methyl-4-chlorophenoxypropionic acid; Purifying the 2-methyl-4-chlorophenoxypropionic acid with an eluent and dissolving the 2-methyl-4-chlorophenoxypropionic acid in a solvent to obtain a refined 2-methyl-4-chlorophenoxypropionic acid solution; Obtaining relationship data between the optical rotation and optical purity of multiple 2-methyl-4-chlorophenoxypropionic acid standard solutions, and fitting the relationship data to obtain a standard curve, wherein the multiple 2-methyl-4-chlorophenoxypropionic acid standard solutions include 2-methyl-4-chlorophenoxypropionic acid standard solutions with optical purities of 95% and 0%; measuring the optical rotation of the purified 2-methyl-4-chlorophenoxypropionic acid solution to obtain a measured optical rotation; The optical purity of the purified 2-methyl-4-chlorophenoxypropionic acid solution is measured according to the measured optical rotation and the standard curve to determine the chiral distribution of the chemical root inhibitor; The step of saponifying a chemical root inhibitor containing 2-methyl-4-chlorophenoxypropionate comprises: Mixing materials containing a chemical root inhibitor, an organic solvent, and an alkali solution under preset conditions to obtain a mixed solution; performing rotary evaporation on the mixed solution to remove the organic solvent and obtain an aqueous solution; adding dichloromethane to the aqueous solution to obtain an upper aqueous phase; After adjusting the pH of the upper aqueous phase to 5.8-6.2, the dichloromethane is added to obtain a lower organic phase, which is subjected to rotary evaporation and drying to obtain the 2-methyl-4-chlorophenoxypropionic acid; In the step of mixing the materials containing the chemical root inhibitor, the organic solvent and the alkali solution under preset conditions, the ratio of the mass of the chemical root inhibitor to the volume of the organic solvent and the volume of the alkali solution is 1:15~25:15~25.

2. The measuring method according to claim 1, wherein In the step of mixing the materials containing the chemical root inhibitor, the organic solvent and the alkali solution under preset conditions, the concentration of the alkali solution is 0.1-0.5 g / mL.

3. The measuring method according to claim 2, characterized in that The step of adjusting the pH of the upper aqueous phase to 5.8-6.2 comprises: An acid solution of a preset concentration is added to the upper aqueous phase to adjust the pH to 5.8-6.

2.

4. The measuring method according to claim 1, wherein The step of adjusting the pH of the upper aqueous phase to 5.8-6.2 comprises: The upper aqueous phase was subjected to column separation treatment and the pH was adjusted to 5.8-6.

2.

5. The measuring method according to claim 1, characterized in that In the step of purifying the 2-methyl-4-chlorophenoxypropionic acid by using an eluent and dissolving the 2-methyl-4-chlorophenoxypropionic acid in a solvent, the eluent includes at least one of dichloromethane and methanol.

6. The measuring method according to claim 1, characterized in that In the refined 2-methyl-4-chlorophenoxypropionic acid solution and the plurality of 2-methyl-4-chlorophenoxypropionic acid standard solutions, the solvent includes at least one of dichloromethane, toluene, chloroform and petroleum ether.

7. The measuring method according to claim 1, characterized in that The concentrations of the purified 2-methyl-4-chlorophenoxypropionic acid solution and the multiple 2-methyl-4-chlorophenoxypropionic acid standard solutions are both 0.1-0.3 g / mL.

8. The measurement method according to claim 1, characterized in that The correlation coefficient of the standard curve is 0.99~0.999.

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