Detection method of dimethyl monoethanolamine content and its application

Abstract

The present application embodiment proposes a method for detecting the content of dimethyl monoethanolamine and its use. The detection method includes: under alkaline conditions, reacting dimethyl monoethanolamine standard solutions of different concentrations with 4-nitrobenzyl chloride in a water bath to obtain standard samples of different concentrations; performing high-performance liquid chromatography ultraviolet detection on the standard samples of different concentrations to obtain the peak area of dimethyl monoethanolamine in the standard samples of different concentrations; and obtaining a linear equation for the corresponding relationship between concentration x and peak area y; performing high-performance liquid chromatography ultraviolet detection on the sample to be tested to obtain the peak area of dimethyl monoethanolamine in the sample to be tested, and calculating the concentration of dimethyl monoethanolamine in the sample to be tested; the detection method provided by the embodiment of the present application can more accurately detect the dimethyl monoethanolamine content in hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride, and the detection method is more efficient.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of analytical chemistry, and specifically to a method for detecting the content of dimethyl monoethanolamine and its application. Background Art

[0002] Dimethylmonoethanolamine (DMEA) is an important chemical raw material with multiple reactivity. It can be used to synthesize various target compounds, such as hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride, by reacting with other chemical substances.

[0003] Currently, hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride, produced by quaternization of dimethyl monoethanolamine with 1,3-dichloro-2-propanol, contains a certain amount of dimethyl monoethanolamine residue. Studies have shown that dimethyl monoethanolamine is a severe irritant to the eyes, skin, mucous membranes, and upper respiratory tract, and can cause skin burns. Furthermore, dimethyl monoethanolamine is sensitizing and may cause skin allergies. Therefore, when using dimethyl monoethanolamine as a raw material to produce hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride, the residual amount in the product should be limited.

[0004] However, due to the short UV absorption wavelength of dimethyl monoethanolamine (DMEA) (around 210 nm) and its weak UV absorption, almost all substances respond at this wavelength, which seriously interferes with liquid chromatography UV detection. Furthermore, DMEA is soluble in both water and polar organic solvents, making it difficult to purify in pre-treatment. Furthermore, its short retention time in liquid chromatography columns prevents effective separation from impurities, thus affecting the accuracy of test results.

[0005] In view of this, the present invention proposes a method for detecting the content of dimethyl monoethanolamine. Summary of the Invention

[0006] The purpose of the embodiments of the present application is to provide a method for detecting the content of dimethyl monoethanolamine and its use.

[0007] To achieve the above objectives, the present application proposes the following technical solutions:

[0008] In a first aspect, the present invention provides a method for detecting the content of dimethyl monoethanolamine, the method comprising:

[0009] Prepare dimethyl monoethanolamine standard solutions of different concentrations; react the dimethyl monoethanolamine standard solutions of different concentrations with 4-nitrobenzyl chloride in a water bath under alkaline conditions to obtain standard samples of different concentrations; wherein the 4-nitrobenzyl chloride serves as a derivatization reagent;

[0010] Performing high performance liquid chromatography ultraviolet detection on standard samples of different concentrations to obtain the peak areas of dimethyl monoethanolamine in the standard samples of different concentrations; obtaining a linear equation for the corresponding relationship between concentration x and peak area y based on the peak areas corresponding to the standard samples of different concentrations;

[0011] Prepare a hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution; under alkaline conditions, react the hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution with 4-nitrobenzyl chloride in a water bath to obtain a sample to be tested;

[0012] The sample to be tested is subjected to high performance liquid chromatography ultraviolet detection to obtain the peak area of dimethyl monoethanolamine in the sample to be tested; the peak area of dimethyl monoethanolamine in the sample to be tested is substituted into a linear equation to calculate the concentration of dimethyl monoethanolamine in the sample to be tested.

[0013] As an embodiment, under alkaline conditions, reacting dimethylmonoethanolamine standard solutions of different concentrations with 4-nitrobenzyl chloride in a water bath to obtain standard samples of different concentrations comprises:

[0014] Alkaline reagent, acetonitrile and 4-nitrobenzyl chloride were added to dimethylmonoethanolamine standard solutions of different concentrations, and the mixture was placed in a 60℃ water bath for reaction.

[0015] After the reaction, the volume was adjusted with distilled water, bubbles were removed by ultrasonication, and standard samples of different concentrations were obtained after filtration.

[0016] As an embodiment, the method of preparing a hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution and reacting the hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution with 4-nitrobenzyl chloride in a water bath under alkaline conditions to obtain a sample to be tested comprises:

[0017] Prepare a hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution, add an alkali reagent, acetonitrile and 4-nitrobenzyl chloride to the hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution respectively, and place in a 60°C water bath to react;

[0018] After the reaction, the volume was adjusted with distilled water, bubbles were removed by ultrasonication, and the sample to be tested was obtained after filtration.

[0019] As an embodiment, the alkaline reagent is sodium carbonate.

[0020] As an embodiment, the linear equation is:

[0021] y=56.6280x-2.1918, correlation coefficient R=0.99921.

[0022] As an embodiment, the chromatographic column used in the high performance liquid chromatography ultraviolet detection is Agilent ZORBAXEXTEND-C18.

[0023] As an embodiment, the column temperature of the chromatographic column is 30°C.

[0024] As an embodiment, the chromatographic conditions of the high performance liquid chromatography ultraviolet detection include:

[0025] The detection wavelength was 260–270 nm, and the injection volume was 20 μL;

[0026] Mobile phase A was acetonitrile;

[0027] Mobile phase B was a mixed solution of acetonitrile, water, and phosphoric acid in a volume ratio of 100:898:2.

[0028] As an embodiment, the gradient elution program of mobile phase A and mobile phase B is:

[0029] Elution was performed with mobile phase A and mobile phase B at a volume ratio of 0:100 for 9 min;

[0030] Elution was performed with mobile phase A and mobile phase B in a volume ratio of 70:30 for 5 min;

[0031] Elution was performed with mobile phase A and mobile phase B at a volume ratio of 0:100 for 7 min;

[0032] The flow rate is 1.0 mL / min.

[0033] In a second aspect, the embodiments of the present application provide the use of the detection method described in the first aspect in the quality control of hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride products.

[0034] Compared with the prior art, the embodiments of the present application have at least the following beneficial effects:

[0035] In the detection method of the present invention, 4-nitrobenzyl chloride is used as a derivatization reagent. Under alkaline conditions, dimethyl monoethanolamine and 4-nitrobenzyl chloride undergo a nucleophilic substitution reaction in a water bath to produce (4-nitro)benzylhydroxyethyldimethylammonium chloride. The resulting (4-nitro)benzylhydroxyethyldimethylammonium chloride has strong ultraviolet absorption and is suitable for high-performance liquid chromatography ultraviolet detection.

[0036] Specifically, (4-nitro)benzylhydroxyethyldimethylammonium chloride is extremely easy to separate in high-performance liquid chromatography, and can achieve the purpose of rapid separation and detection through high-performance liquid chromatography, thereby easily eliminating matrix effect interference and improving detection accuracy; therefore, the detection method of the embodiment of the present application is not only easy to operate, but also can effectively improve the separation effect, detection accuracy and precision.

[0037] In summary, the detection method provided in the embodiment of the present application can more accurately detect the content of dimethyl monoethanolamine in hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride, and the detection method is more efficient; thus, the embodiment of the present application solves the problem of impurity interference in the existing detection method of dimethyl monoethanolamine, and has a better application prospect in the quality control of hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride.

[0038] Additional aspects and advantages of the present application will be given in part in the following description, which will become apparent from the following description, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram showing the effect of derivatization reaction temperature on the peak area of dimethyl monoethanolamine;

[0040] Figure 2 Shown is a liquid chromatogram of dimethyl monoethanolamine in this embodiment;

[0041] Figure 3 A schematic diagram showing the linear equation of dimethylmonoethanolamine concentration and peak area is shown. DETAILED DESCRIPTION

[0042] The following will be combined with the embodiments of the present application and the accompanying drawings to clearly and completely describe the technical solutions in the embodiments. Obviously, the embodiments described below are only some of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0043] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0044] It should also be understood that the terms used in this specification of the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present application. As used in the specification of the embodiments of the present application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0045] The following describes in detail the method for detecting the dimethyl monoethanolamine content in the embodiments of the present application and its application.

[0046] First, the detection method of the first aspect of this embodiment is described.

[0047] Detection method

[0048] In the prior art, hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride can be produced by the quaternization reaction of dimethyl monoethanolamine and 1,3-dichloro-2-propanol. The specific reaction is as follows:

[0049] .

[0050] Based on the above reaction, those skilled in the art will recognize that a certain amount of dimethylmonoethanolamine residue will remain in hydroxypropyl bis-hydroxyethyldimethylammonium chloride produced by quaternization of dimethylmonoethanolamine with 1,3-dichloro-2-propanol. Given that dimethylmonoethanolamine is a severe irritant to the eyes, skin, mucous membranes, and upper respiratory tract, and can cause skin burns, it is also sensitizing and may cause skin allergies. Therefore, when using dimethylmonoethanolamine as a raw material to produce hydroxypropyl bis-hydroxyethyldimethylammonium chloride, the residual amount in the product should be limited.

[0051] However, due to the short UV absorption wavelength of dimethyl monoethanolamine (DMEA) (around 210 nm) and its weak UV absorption, almost all substances respond at this wavelength, which seriously interferes with liquid chromatography UV detection. Furthermore, DMEA is soluble in both water and polar organic solvents, making it difficult to purify in pre-treatment. Furthermore, its short retention time in liquid chromatography columns prevents effective separation from impurities, thus affecting the accuracy of test results.

[0052] In view of this, this embodiment provides a method for detecting the content of dimethyl monoethanolamine.

[0053] Specifically, the detection method of this embodiment includes the following steps:

[0054] (1) preparing dimethyl monoethanolamine standard solutions of different concentrations; reacting the dimethyl monoethanolamine standard solutions of different concentrations with 4-nitrobenzyl chloride in a water bath under alkaline conditions to obtain standard samples of different concentrations; wherein the 4-nitrobenzyl chloride is used as a derivatization reagent.

[0055] It is understood that the alkaline conditions described in this embodiment are pH values greater than 7;

[0056] The reaction of step (1) is as follows: .

[0057] In this step, 4-nitrobenzyl chloride is used as a derivatization reagent to induce a nucleophilic substitution reaction between dimethylmonoethanolamine and 4-nitrobenzyl chloride under alkaline conditions to produce (4-nitro)benzylhydroxyethyldimethylammonium chloride. The resulting (4-nitro)benzylhydroxyethyldimethylammonium chloride is easily separated in high-performance liquid chromatography (HPLC) and exhibits enhanced UV absorption, making it suitable for HPLC UV detection.

[0058] Based on this, the (4-nitro)benzylhydroxyethyldimethylammonium chloride generated by derivatization can achieve the purpose of rapid separation and detection through high performance liquid chromatography, thereby easily eliminating the interference of matrix effects and improving detection accuracy and precision.

[0059] Next, the standard sample obtained above is subjected to high performance liquid chromatography ultraviolet detection;

[0060] (2) High performance liquid chromatography ultraviolet detection is performed on standard samples of different concentrations to obtain the peak areas of dimethyl monoethanolamine in the standard samples of different concentrations; based on the peak areas corresponding to the standard samples of different concentrations, a linear equation for the corresponding relationship between concentration x and peak area y is obtained.

[0061] In step (2), linear regression is performed with the concentration of dimethyl monoethanolamine as the abscissa x and the peak area as the ordinate y to obtain a corresponding linear equation.

[0062] Specifically, the above linear equation is: y=56.6280x-2.1918, and the correlation coefficient R=0.99921.

[0063] In this step, as described above, the standard sample after the above-mentioned derivatization reaction is separated and detected by high-performance liquid chromatography ultraviolet; among them, the (4-nitro)benzylhydroxyethyldimethylammonium chloride generated by derivatization is very easy to separate in high-performance liquid chromatography, and the purpose of separation and detection can be achieved through high-performance liquid chromatography, thereby easily eliminating the interference of matrix effects and improving detection accuracy.

[0064] At the same time, in step (2), based on the above test results (peak area of dimethyl monoethanolamine), a linear equation (calibration model) for the corresponding relationship between concentration x and peak area y can be obtained; based on this linear equation, when the content of the sample to be tested is tested, the content (concentration) of dimethyl monoethanolamine in the hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution can be quickly calculated based on the peak area of the sample to be tested.

[0065] It is understood that the high performance liquid chromatography ultraviolet detection of this embodiment can be performed in a high performance liquid chromatograph, for example, an Agilent 1260 liquid chromatograph;

[0066] (3) preparing a hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution; reacting the hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution with 4-nitrobenzyl chloride in a water bath under alkaline conditions to obtain a sample to be tested.

[0067] It is understood that the alkaline condition described in this embodiment is a pH value greater than 7.

[0068] The principle of step (3) is the same as that of step (1). In step (3), dimethylmonoethanolamine in the hydroxypropylbis-hydroxyethyldimethylammonium chloride solution is reacted with 4-nitrobenzyl chloride to undergo a nucleophilic substitution reaction to generate (4-nitro)benzylhydroxyethyldimethylammonium chloride. The (4-nitro)benzylhydroxyethyldimethylammonium chloride generated by derivatization is very easy to separate in the subsequent high performance liquid chromatography, which can effectively eliminate the interference of matrix effect and improve the accuracy of the detection result.

[0069] After the sample to be tested is obtained by the reaction in step (3), the sample to be tested is subjected to high performance liquid chromatography ultraviolet detection and substituted into the linear equation for calculation;

[0070] (4) performing high performance liquid chromatography ultraviolet detection on the sample to be tested to obtain the peak area of dimethyl monoethanolamine in the sample to be tested; substituting the peak area of dimethyl monoethanolamine in the sample to be tested into a linear equation to calculate the concentration of dimethyl monoethanolamine in the sample to be tested.

[0071] In step (4), the sample to be tested obtained in step (3) is injected into a high performance liquid chromatograph for high performance liquid ultraviolet detection to obtain the peak area of dimethyl monoethanolamine; the obtained peak area of dimethyl monoethanolamine is substituted into the linear equation obtained in step (2) to calculate the concentration of dimethyl monoethanolamine.

[0072] Therefore, in this embodiment, the sample to be tested after the derivatization reaction is separated and detected by high performance liquid chromatography ultraviolet light; the peak area of dimethylmonoethanolamine in the sample to be tested is obtained. At the same time, based on the linear equation (calibration model) obtained in step (2), the content of dimethylmonoethanolamine in the hydroxypropyl bis-hydroxyethyldimethylammonium chloride solution can be quickly determined based on the peak area of the sample to be tested.

[0073] In summary, the detection method provided in this embodiment can more accurately detect the content of dimethyl monoethanolamine in hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride by converting dimethyl monoethanolamine into its derivative (4-nitro)benzyl hydroxyethyl dimethyl ammonium chloride, and the detection method is more efficient.

[0074] Therefore, this embodiment solves the problem of impurity interference in the existing detection method of dimethyl monoethanolamine and has a better application prospect in the quality control of hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride.

[0075] The CAS number of the dimethyl monoethanolamine of the present embodiment is 108-01-0.

[0076] The following further describes the relevant steps of the above detection method.

[0077] Step (1) is to prepare dimethyl monoethanolamine standard solutions of different concentrations; under alkaline conditions, react the dimethyl monoethanolamine standard solutions of different concentrations with 4-nitrobenzyl chloride in a water bath to obtain standard samples of different concentrations; which can be:

[0078] Weigh 0.2004 g of dimethyl monoethanolamine standard, dissolve it in distilled water, dilute to 100 mL, and shake well; use a pipette to transfer 10 mL to another 100 mL volumetric flask, dilute to volume, and mix well to obtain a stock solution.

[0079] In this embodiment, after obtaining the stock solution, dimethyl monoethanolamine standard solutions of different concentrations can be prepared based on the stock solution, and an alkali reagent and 4-nitrobenzyl chloride are added to the dimethyl monoethanolamine standard solution, and the solution is placed in a water bath for reaction to obtain standard samples of different concentrations.

[0080] In this embodiment, an alkaline environment is created by adding an alkaline reagent, sodium carbonate.

[0081] Specifically, under alkaline conditions, dimethylmonoethanolamine standard solutions of different concentrations are reacted with 4-nitrobenzyl chloride in a water bath to obtain standard samples of different concentrations, including:

[0082] (1.1) Add an alkali reagent, acetonitrile, and 4-nitrobenzyl chloride to standard solutions of dimethylmonoethanolamine at different concentrations and place in a 60°C water bath for reaction.

[0083] (1.2) After the reaction is completed, distilled water is used to make up the volume, and bubbles are removed by ultrasonication. Standard samples of different concentrations are obtained after filtration.

[0084] After preparing the above-mentioned stock solution (dimethylmonoethanolamine stock solution with a concentration of 200.4 mg / L), 0.50 mL, 1.00 mL, 2.00 mL, 3.00 mL, and 4.00 mL of the stock solution were respectively measured and placed in a 50 mL volumetric flask, and the volume was made up to 10 mL with distilled water. 1 mL of 5% sodium carbonate was added, and 0.5 mL of 1% 4-nitrobenzyl chloride and 5 mL of acetonitrile were added dropwise. The mixtures were placed in a 60° C. water bath for reaction for 1-3 hours.

[0085] Typically, after the reaction is completed, phosphoric acid (e.g., 2 mL of 10% phosphoric acid) is added to terminate the reaction, and then the volume is adjusted to the mark with distilled water. Air bubbles are removed by ultrasonication, and a series of standard samples are obtained by filtering with a syringe filter.

[0086] Typically, the ultrasound duration is 3 to 5 minutes, preferably 5 minutes.

[0087] In this example, 4-nitrobenzyl chloride was added in the form of a 4-nitrobenzyl chloride solution.

[0088] The preparation method of the 4-nitrobenzyl chloride solution is as follows: 1 g of 4-nitrobenzyl chloride is weighed, dissolved in 99 g of acetonitrile, and dissolved by ultrasonication to obtain a 4-nitrobenzyl chloride solution with a mass concentration of 1%.

[0089] See also Figure 1 This example, through relevant experiments, found that the derivatization reaction temperature affects the chromatogram peak area; as the temperature increases, the peak area increases, and after reaching the peak, it decreases with increasing temperature. The peak area is maximum at 60°C, indicating that this temperature is effective for derivatization and is conducive to the detection results.

[0090] In step (2), after preparing the above-mentioned standard samples of different concentrations, the standard samples of different concentrations are subjected to high performance liquid chromatography ultraviolet detection to obtain the peak areas of dimethyl monoethanolamine in the standard samples of different concentrations; and based on the peak areas corresponding to the standard samples of different concentrations, a linear equation for the corresponding relationship between concentration x and peak area y is obtained.

[0091] As an embodiment, the chromatographic column used for high performance liquid chromatography ultraviolet detection in this example is Agilent ZORBAX EXTEND-C18, and the column temperature of the chromatographic column is 30°C.

[0092] The chromatographic conditions for the above-mentioned high performance liquid chromatography ultraviolet detection include:

[0093] The detection wavelength was 260–270 nm (preferably 262 nm), and the injection volume was 20 μL;

[0094] Mobile phase A was acetonitrile;

[0095] Mobile phase B was a mixed solution of acetonitrile, water, and phosphoric acid in a volume ratio of 100:898:2.

[0096] The high performance liquid chromatography ultraviolet detection of this embodiment adopts gradient elution. Specifically, the gradient elution program of the mobile phase A and the mobile phase B is:

[0097] Elution was performed with mobile phase A and mobile phase B at a volume ratio of 0:100 for 9 min;

[0098] Elution was performed with mobile phase A and mobile phase B in a volume ratio of 70:30 for 5 min;

[0099] Elution was performed with mobile phase A and mobile phase B at a volume ratio of 0:100 for 7 min;

[0100] The flow rate is 1.0 mL / min.

[0101] In step (3), the preparation of a hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution; reacting the hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution with 4-nitrobenzyl chloride in a water bath under alkaline conditions to obtain a sample to be tested, comprising:

[0102] (3.1) Prepare a hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution. Add an alkaline reagent, acetonitrile, and 4-nitrobenzyl chloride to the hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution, and place in a 60°C water bath for reaction.

[0103] (3.2) After the reaction is completed, distilled water is added to the volume, bubbles are removed by ultrasonication, and the sample to be tested is obtained after filtration.

[0104] Exemplarily, the above steps may be:

[0105] Weigh 0.5 g (accurate to 1 mg) of hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride and place it in a 50 mL volumetric flask. Fill the flask with distilled water to 10 mL, add 1 mL of 5% sodium carbonate, dropwise add 0.5 mL of 1% 4-nitrobenzyl chloride and 5 mL of acetonitrile, and place in a 60°C water bath for 1-3 hours to carry out the derivatization reaction.

[0106] Typically, after the reaction is completed, phosphoric acid (e.g., 2 mL of 10% phosphoric acid) is added to terminate the reaction, and then the volume is adjusted to the mark with distilled water. Air bubbles are removed by ultrasonication, and the sample to be tested is filtered with a syringe filter.

[0107] Typically, the ultrasound duration is 3 to 5 minutes, preferably 5 minutes.

[0108] As mentioned above, the alkaline conditions described in this embodiment are pH values greater than 7. In this embodiment, an alkaline environment is created by adding an alkaline reagent, sodium carbonate.

[0109] As an embodiment, the alkaline reagent is sodium carbonate.

[0110] It is understood that step (3) is to allow dimethylmonoethanolamine in the hydroxypropylbis-hydroxyethyldimethylammonium chloride solution to undergo a nucleophilic substitution reaction with 4-nitrobenzyl chloride to generate (4-nitro)benzylhydroxyethyldimethylammonium chloride; wherein, please refer to Figure 2 The (4-nitro)benzylhydroxyethyldimethylammonium chloride generated by derivatization is very easy to separate in the subsequent high performance liquid chromatography, which can effectively eliminate the interference of matrix effects and improve the accuracy of the detection results.

[0111] As described above, in step (4), the sample to be tested obtained in step (3) is injected into a high performance liquid chromatograph for high performance liquid ultraviolet detection to obtain the peak area of dimethyl monoethanolamine; the obtained peak area of dimethyl monoethanolamine is substituted into the linear equation obtained in step (2) to calculate the concentration of dimethyl monoethanolamine.

[0112] It is understandable that in the testing process in steps (2) and (4), the sample (standard sample or sample to be tested) is injected into the high performance liquid chromatograph for high performance liquid ultraviolet detection.

[0113] The high performance liquid chromatography ultraviolet detection conditions in step (4) are the same as those in step (2).

[0114] Specifically, the chromatographic column used for high performance liquid chromatography ultraviolet detection in step (4) is Agilent ZORBAXEXTEND-C18, and the column temperature of the chromatographic column is 30°C.

[0115] Among them, the chromatographic conditions of high performance liquid chromatography ultraviolet detection include:

[0116] The detection wavelength was 260–270 nm (preferably 262 nm), and the injection volume was 20 μL;

[0117] Mobile phase A was acetonitrile;

[0118] Mobile phase B was a mixed solution of acetonitrile, water, and phosphoric acid in a volume ratio of 100:898:2.

[0119] The high performance liquid chromatography ultraviolet detection in step (4) also adopts gradient elution; specifically, the gradient elution program of mobile phase A and mobile phase B is:

[0120] Elution was performed with mobile phase A and mobile phase B at a volume ratio of 0:100 for 9 min;

[0121] Elution was performed with mobile phase A and mobile phase B in a volume ratio of 70:30 for 5 min;

[0122] Elution was performed with mobile phase A and mobile phase B at a volume ratio of 0:100 for 7 min;

[0123] The flow rate is 1.0 mL / min.

[0124] In summary, in this example, 4-nitrobenzyl chloride is used as a derivatization reagent. Under alkaline conditions, dimethylmonoethanolamine and 4-nitrobenzyl chloride undergo a nucleophilic substitution reaction in a water bath to produce (4-nitro)benzylhydroxyethyldimethylammonium chloride. The derivatized (4-nitro)benzylhydroxyethyldimethylammonium chloride is easily separated in high-performance liquid chromatography (HPLC), enabling separation and detection by HPLC. This makes it easy to eliminate matrix effect interference and improve detection accuracy. The detection method of this example is not only easy to operate, but also effectively improves separation efficiency, detection accuracy, and precision.

[0125] Next, the use of the second aspect of this embodiment will be described.

[0126] use

[0127] It is understandable that, since hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride products produced using dimethyl monoethanolamine as a raw material will contain a certain amount of dimethyl monoethanolamine, and hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride is commonly used in skin care products or personal washes, this residual dimethyl monoethanolamine can easily come into contact with or be ingested by the human body, either directly or indirectly. Therefore, when using dimethyl monoethanolamine as a raw material to produce hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride, the residual amount of hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride should be limited.

[0128] As described above, the detection method provided in this embodiment can more accurately and quickly detect the content of dimethyl monoethanolamine in hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride, and the detection method is highly efficient; therefore, the detection method can meet the needs of safety risk screening of dimethyl monoethanolamine in hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride, and can provide better technical support for the quality control and safety monitoring of hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride, suggesting that the detection method has better application prospects in the quality control of hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride.

[0129] The present application will be further described below with reference to specific examples. It should be understood that these examples are only used to illustrate / explain the present application and are not intended to limit the scope of the present application.

[0130] In the following examples, all materials, reagents and instruments used can be purchased from commercial sources unless otherwise specified.

[0131] It should be noted that, in the following examples, unless otherwise specified, the method and conditions for analysis (separation and detection) using a high performance liquid chromatograph are as follows:

[0132] The preparation method of 4-nitrobenzyl chloride solution is as follows: weigh 1 g of 4-nitrobenzyl chloride, dissolve it in 99 g of acetonitrile, and dissolve it by ultrasonication to obtain a 4-nitrobenzyl chloride solution with a mass concentration of 1%.

[0133] A high performance liquid chromatograph (HPLC) was used, and the concentration of phosphoric acid solution in mobile phase B was 85%.

[0134] Mobile phase A was acetonitrile; mobile phase B was acetonitrile: water: phosphoric acid = 100:898:2 (volume ratio).

[0135] The gradient elution program is shown in Table 1 below:

[0136] Table 1:

[0137] Time (min) Mobile phase A (%) Mobile phase B (%) Flow rate (mL / min) 0.00 0 100 1 9.00 0 100 1 10.00 70 30 1 15.00 70 30 1 16.00 0 100 1 23.00 0 100 1

[0138] Among them, the chromatographic column selected is Agilent ZORBAX SB-C8, the chromatographic column length is 250 mm, the chromatographic column inner diameter is 4.6 mm, and the chromatographic column filler particle diameter is 5 μm; the detection wavelength is set to 262 nm, the column temperature is 30°C, and the injection volume is 20 μL.

[0139] Examples 1-10:

[0140] This example found that the derivatization temperature of dimethyl monoethanolamine affects its peak area. Therefore, by setting a gradient water bath temperature, the peak area of dimethyl monoethanolamine was detected, specifically:

[0141] Weigh 0.2004 g of dimethylmonoethanolamine standard, dissolve it in distilled water, dilute to 100 mL, and shake well. Pipette 10 mL into another 100 mL volumetric flask, dilute to volume, and mix well to obtain a stock solution with a concentration of 200.4 mg / L.

[0142] Take 10 50mL volumetric flasks, transfer 2mL of 200.4mg / L dimethylmonoethanolamine stock solution into each volumetric flask, make up to 10mL with distilled water, add 1mL of 5% sodium carbonate, 0.5mL of 1% 4-nitrobenzyl chloride, and 5mL of acetonitrile, and mix thoroughly. Place in a water bath at 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, and 80℃ for 1 hour respectively. After the reaction is completed, remove the volumetric flask, add 2mL of 10% phosphoric acid to terminate the reaction, make up to the mark with distilled water, and remove bubbles by sonication for 5 minutes. Filter with a syringe filter into a sample bottle. Inject the sample into a high-performance liquid chromatograph for separation and detection. The test results are shown in Table 2:

[0143] The water bath temperature is the horizontal axis and the peak area is the vertical axis. The test results are as follows: Figure 1 As shown;

[0144] Table 2: Water bath temperature and resolution

[0145]

[0146] Based on Table 2 and Figure 1 The test results show that the peak area of dimethylmonoethanolamine increases with increasing temperature. After reaching the peak, it decreases with increasing temperature. The peak area is maximum at 60°C, indicating that this temperature provides the best derivatization effect. Therefore, the derivatization temperature was determined to be 60°C.

[0147] Among them, the liquid chromatogram after separation is as follows Figure 2 As shown. Combined Figure 2 As can be seen from the liquid chromatogram, no interference peaks appear in the liquid chromatogram; that is, this embodiment uses 4-nitrobenzyl chloride as a derivatization reagent to effectively eliminate matrix effect interference and improve the accuracy of the detection results.

[0148] Accuracy experiment

[0149] Examples 11-15:

[0150] Weigh 0.2004 g of dimethylmonoethanolamine standard into a 100 mL volumetric flask and dilute to the mark with distilled water, resulting in a concentration of 2004 mg / L. Transfer 10 mL to another 100 mL volumetric flask and dilute to the mark with distilled water to prepare a stock solution (concentration of 200.4 mg / L) for later use.

[0151] Next, 0.50 mL, 1.00 mL, 2.00 mL, 3.00 mL, and 4.00 mL of the stock solution were respectively measured and placed in five 50 mL volumetric flasks, and the volume was filled to 10 mL with distilled water. 1 mL of 5% sodium carbonate was added, and 0.5 mL of 1% 4-nitrobenzyl chloride and 5 mL of acetonitrile were added dropwise. The flasks were placed in a water bath at 60° C. for 1 hour. After the reaction was completed, the volumetric flasks were removed, 2 mL of 10% phosphoric acid was added to terminate the reaction, the volume was filled to the mark with distilled water, and bubbles were removed by ultrasonication for 5 minutes. The standard samples were filtered into sample bottles with a syringe filter, and the samples were injected into a high performance liquid chromatograph for ultraviolet spectrum detection to obtain the peak area of dimethyl monoethanolamine. The test results are shown in Table 3:

[0152] Table 3: Peak area for detection of dimethyl monoethanolamine

[0153] Example Dimethyl monoethanolamine (mg / L) Peak area (mAU·s) Example 11 2.004 191.5 Example 12 4.008 389.6 Example 13 8.016 809.0 Example 14 12.024 1186.3 Example 15 16.032 1624.7

[0154] Combined with the test results in Table 3, with the concentration of dimethyl monoethanolamine as the horizontal coordinate and the peak area as the vertical coordinate, linear regression was performed and the linear equation was obtained: y=56.6280x-2.1918, with a correlation coefficient R=0.99921. The linear equation is as follows Figure 3 As shown in Table 3 and Figure 3The test results show that dimethyl monoethanolamine has good linearity in the concentration range of 0-16 mg / L.

[0155] Examples 16-18:

[0156] Accurately weigh 3 parts of hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride (weights shown in Table 4) (accurate to 1 mg), place them separately in 50 mL volumetric flasks, make up to 10 mL with distilled water, add 1 mL of 5% sodium carbonate, add 0.5 mL of 1% 4-nitrobenzyl chloride and 5 mL of acetonitrile dropwise, and place in a 60°C water bath for 1 hour.

[0157] After the reaction, the volumetric flask was taken out, 2 mL of 10% mass concentration phosphoric acid was added to terminate the reaction, the volume was filled up to the mark with distilled water, and bubbles were removed by ultrasonication for 5 minutes; the solution was filtered into a sample bottle with a syringe filter, and the obtained sample was injected into a high performance liquid chromatograph for ultraviolet spectroscopy detection to obtain the peak area of dimethyl monoethanolamine. The peak area was substituted into the linear equation obtained in the above Examples 11-15, and the content of dimethyl monoethanolamine in each sample was calculated, which was the content of the target substance contained in Examples 16-18, and was recorded as A value.

[0158] Examples 19-21:

[0159] Accurately weigh 3 parts of hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride, the weight is shown in Table 4 (accurate to 1 mg), and place them in 50 mL volumetric flasks respectively. Take the stock solution (200.4 mg / L) prepared in Examples 11-15 as a reference substance (known concentration), add 0.5 mL (parallel group 1), 1 mL (parallel group 2), and 2 mL (parallel group 3), respectively, add distilled water to 10 mL, add 1 mL of 5% mass concentration of sodium carbonate, add 0.5 mL of 1% mass concentration of 4-nitrobenzyl chloride and 5 mL of acetonitrile dropwise, and place in a water bath at 60 ° C for 1 hour.

[0160] After the reaction, the volumetric flask was taken out, 2 mL of 10% mass concentration phosphoric acid was added to terminate the reaction, the volume was filled up to the mark with distilled water, and bubbles were removed by ultrasonication for 5 minutes; the mixture was filtered into a sample bottle with a syringe filter, and the obtained sample was injected into a high performance liquid chromatograph for ultraviolet spectroscopy detection to obtain the peak area of dimethyl monoethanolamine. The peak area was substituted into the linear equation obtained in the above Examples 11-15 to calculate the content of dimethyl monoethanolamine in the sample, which was the content of the target substance contained in Examples 19-21, recorded as the C value.

[0161] The recovery rate is calculated based on the A value and the C value, where the recovery rate formula is:

[0162] ;

[0163] In the above formula: A is the content of the target substance contained in Examples 16-18; B is the increase in sample concentration after adding the reference substance; C is the content of the target substance contained in Examples 19-21.

[0164] The calculation formula for B value is:

[0165] (Concentration of stock solution*volume of stock solution added) / weight of the corresponding test sample in Examples 19-21.

[0166] Among them, each concentration was prepared in triplicate, and three sets of parallel experiments were performed. The recovery rate was determined under the content determination item. The test results are shown in Table 4 below. Among them, the recovery rate in Table 4 was calculated by taking the average value of the A value (i.e., 451.4 mg / kg) and substituting it into the above recovery rate calculation formula to calculate the A value;

[0167] Table 4: Accuracy test results

[0168]

[0169] According to the test results in Table 4, the average recovery rate of the three parallel group experiments is greater than 98%, indicating that the analyte can be effectively enriched during the treatment of the sample, and the RSD is less than 2%, indicating that the detection method of this embodiment has excellent accuracy.

[0170] Precision experiment

[0171] Examples 22-27:

[0172] The dimethyl monoethanolamine solution (standard sample) of Example 13 was taken and injected 6 times continuously. The peak area of the main component was recorded and the precision was calculated. The test results are shown in Table 5 below:

[0173] Table 5: Precision test results

[0174]

[0175] The test results in Table 5 indicate that the detection method of this embodiment has excellent precision and repeatability.

[0176] Solution stability test

[0177] Examples 28-32:

[0178] The dimethyl monoethanolamine solution (standard sample) of Example 13 was taken and injected at room temperature for 4, 8, 12, 24, and 48 hours, and the peak area change of the main component was recorded. The test results are shown in Table 6 below:

[0179] Table 6: Solution stability test results

[0180]

[0181] According to the test results in Table 6, it is shown that the detection method of this embodiment has excellent stability of the derivatization solution within 48 hours at room temperature.

[0182] In summary, this embodiment uses 4-nitrobenzyl chloride as a derivatization reagent. Under alkaline conditions, dimethyl monoethanolamine and 4-nitrobenzyl chloride undergo a nucleophilic substitution reaction in a water bath to produce (4-nitro)benzylhydroxyethyldimethylammonium chloride. The derivatized (4-nitro)benzylhydroxyethyldimethylammonium chloride is easily separated in high-performance liquid chromatography (HPLC), enabling separation and detection by HPLC. This makes it easy to eliminate matrix effect interference and improve detection accuracy. Therefore, the detection method of this embodiment is not only easy to operate, but also effectively improves separation efficiency, detection accuracy, and precision.

[0183] The above is a detailed introduction to the technical solutions provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present application. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present application. At the same time, for those skilled in the art, according to the embodiments of the present application, there may be changes in the specific implementation methods and application scope. In summary, the contents of this specification should not be understood as limiting the present application.

Claims

1. A method for detecting the content of dimethyl monoethanolamine, characterized in that: The detection method comprises: Prepare dimethyl monoethanolamine standard solutions of different concentrations; react the dimethyl monoethanolamine standard solutions of different concentrations with 4-nitrobenzyl chloride in a water bath under alkaline conditions to obtain standard samples of different concentrations; wherein the 4-nitrobenzyl chloride serves as a derivatization reagent; Performing high performance liquid chromatography ultraviolet detection on standard samples of different concentrations to obtain the peak areas of dimethyl monoethanolamine in the standard samples of different concentrations; obtaining a linear equation for the corresponding relationship between concentration x and peak area y based on the peak areas corresponding to the standard samples of different concentrations; Prepare a hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution; under alkaline conditions, react the hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution with 4-nitrobenzyl chloride in a water bath to obtain a sample to be tested; Performing high performance liquid chromatography ultraviolet detection on the sample to be tested to obtain the peak area of dimethyl monoethanolamine in the sample to be tested; substituting the peak area of dimethyl monoethanolamine in the sample to be tested into a linear equation to calculate the concentration of dimethyl monoethanolamine in the sample to be tested; The chromatographic column used for the high performance liquid chromatography ultraviolet detection is Agilent ZORBAX EXTEND-C18; The chromatographic conditions of the high performance liquid chromatography ultraviolet detection include: The detection wavelength was 260–270 nm, and the injection volume was 20 μL; Mobile phase A was acetonitrile; Mobile phase B was a mixed solution of acetonitrile, water, and phosphoric acid in a volume ratio of 100:898:2; The gradient elution program of mobile phase A and mobile phase B is: 。 2. The detection method according to claim 1, wherein Under alkaline conditions, dimethylmonoethanolamine standard solutions of different concentrations are reacted with 4-nitrobenzyl chloride in a water bath to obtain standard samples of different concentrations, including: Alkaline reagent, acetonitrile and 4-nitrobenzyl chloride were added to dimethylmonoethanolamine standard solutions of different concentrations, and the mixture was placed in a 60℃ water bath for reaction. After the reaction, the volume was adjusted with distilled water, bubbles were removed by ultrasonication, and standard samples of different concentrations were obtained after filtration.

3. The detection method according to claim 1, wherein The prepared hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution; Under alkaline conditions, a hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution is reacted with 4-nitrobenzyl chloride in a water bath to obtain a sample to be tested, including: Prepare a hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution, add an alkali reagent, acetonitrile and 4-nitrobenzyl chloride to the hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride solution respectively, and place it in a 60°C water bath for reaction; After the reaction, the volume was adjusted with distilled water, bubbles were removed by ultrasonication, and the sample to be tested was obtained after filtration.

4. The detection method according to claim 2 or 3, characterized in that The alkaline reagent is sodium carbonate.

5. The detection method according to claim 1, wherein The linear equation is: y=56.6280x-2.1918, correlation coefficient R=0.99921.

6. The detection method according to claim 1, characterized in that The column temperature of the chromatographic column is 30°C.

7. Use of the detection method according to any one of claims 1 to 6 in quality control of hydroxypropyl bis-hydroxyethyl dimethyl ammonium chloride products.

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