Detection method of acrylamide content in polyacrylamide and its application

Abstract

The present application embodiment proposes a method for detecting the content of acrylamide in polyacrylamide and its use. The detection method comprises: reacting acrylamide standard solutions of different concentrations with inorganic acid solution and thiosalicylic acid in a water bath respectively 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 ​​acrylamide in the standard samples of different concentrations, and obtaining a linear equation of 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 ​​acrylamide in the sample to be tested; substituting the peak area of ​​acrylamide in the sample to be tested into the linear equation to calculate the concentration of acrylamide in the sample to be tested; the detection method of the present application embodiment is not only easy to operate, but also can effectively improve the separation effect, detection accuracy and precision.

Description

Technical Field

[0001] The present application relates to the technical field of analytical chemistry, and in particular to a method for detecting acrylamide content in polyacrylamide and uses thereof. Background Art

[0002] Acrylamide is an organic compound with neurotoxicity, immunotoxicity, reproductive toxicity and potential carcinogenicity. At present, there will be a certain amount of residual acrylamide in the cationic polyacrylamide produced with acrylamide as raw material. Given that cationic polyacrylamide is widely used in water treatment and hair care, this leads to the residual acrylamide being directly or indirectly contacted or ingested by the human body. Therefore, when using acrylamide as raw material to produce polyacrylamide, the residual amount in the polyacrylamide should be limited.

[0003] In the prior art, the detection methods of residual acrylamide include chemical methods and instrumental methods. Among them, the chemical method includes bromine titration, and the instrumental method includes high performance liquid chromatography, high performance liquid chromatography tandem mass spectrometry or gas chromatography tandem mass spectrometry. In the high performance liquid chromatography detection, since the detection wavelength of acrylamide is relatively short, at about 200nm, at this wavelength, almost all substances have a response, and the interference is serious when the sample composition is complex. Because of its good water solubility, the retention time in most chromatographic columns is not long, so that acrylamide and impurities cannot be separated, affecting the accuracy of the results.

[0004] At present, the most widely used detection method is high performance liquid phase tandem mass spectrometry; however, this detection method uses deuterated acrylamide as an internal standard, which is complicated to operate. Gas phase tandem mass spectrometry requires acrylamide to be brominated to generate 2,3-dibromopropionamide, which is then separated and purified for analysis. It also has the problem of complex operation and high requirements for detection personnel.

[0005] In view of this, the present application provides a method for detecting the acrylamide content in polyacrylamide. Summary of the invention

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

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

[0008] In a first aspect, the present application provides a method for detecting acrylamide content in polyacrylamide, the detection method comprising:

[0009] Prepare acrylamide standard solutions of different concentrations; react the acrylamide standard solutions of different concentrations with an inorganic acid solution and thiosalicylic acid in a water bath to obtain standard samples of different concentrations;

[0010] Performing high performance liquid chromatography ultraviolet detection on standard samples of different concentrations to obtain the peak areas of acrylamide in the standard samples of different concentrations; obtaining a linear equation of 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 polyacrylamide solution, react the polyacrylamide solution with an inorganic acid solution and thiosalicylic acid 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 ​​acrylamide in the sample to be tested; the peak area of ​​acrylamide in the sample to be tested is substituted into a linear equation to calculate the concentration of acrylamide in the sample to be tested.

[0013] As an embodiment, the acrylamide standard solutions of different concentrations are reacted with the inorganic acid solution and thiosalicylic acid in a water bath to obtain standard samples of different concentrations, including:

[0014] Inorganic acid solution and thiosalicylic acid were added to standard acrylamide solutions of different concentrations, and the solutions were placed in a 65°C water bath for reaction;

[0015] After the reaction, acetonitrile was added, the volume was fixed with distilled water, and bubbles were removed by ultrasonic wave. Standard samples of different concentrations were obtained after filtration.

[0016] As an embodiment, the polyacrylamide solution is prepared, and the polyacrylamide solution is reacted with an inorganic acid solution and thiosalicylic acid in a water bath to obtain a sample to be tested, comprising:

[0017] Prepare a polyacrylamide solution, add an inorganic acid solution and thiosalicylic acid to the polyacrylamide solution respectively, and place the solution in a 65°C water bath for reaction;

[0018] After the reaction is completed, acetonitrile is added, and the test solution is obtained after the volume is fixed with acetonitrile;

[0019] The test solution was filtered and mixed with an equal volume of distilled water, and air bubbles were removed by ultrasound to obtain the test sample.

[0020] As an embodiment, the inorganic acid solution is a dilute sulfuric acid solution.

[0021] As an implementation method, the linear equation is:

[0022] y=100.6292x+3.1635, correlation coefficient R 2 =0.99979.

[0023] As an embodiment, the chromatographic column used in the high performance liquid chromatography ultraviolet detection is Agilent SB-C8.

[0024] As an embodiment, the column temperature of the chromatographic column is 30°C.

[0025] As an embodiment, the chromatographic conditions of the high performance liquid chromatography ultraviolet detection include:

[0026] The detection wavelength was 250-260 nm, and the injection volume was 20 μL;

[0027] Mobile phase A was acetonitrile;

[0028] The mobile phase B was a mixed solution of acetonitrile, water and phosphoric acid in a volume ratio of 100:898:2.

[0029] As an embodiment, the gradient elution program of mobile phase A and mobile phase B is:

[0030] Elution was performed with mobile phase A and mobile phase B in a volume ratio of 15:85 for 10 min;

[0031] Elution was performed with mobile phase A and mobile phase B in a volume ratio of 80:20 for 5 min;

[0032] Elution was performed with mobile phase A and mobile phase B in a volume ratio of 15:85 for 5 min;

[0033] Among them, the flow rate is 1.0mL / min.

[0034] 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 polyacrylamide products.

[0035] The embodiments of the present application have at least the following beneficial effects:

[0036] In the embodiment of the present application, thiosalicylic acid is used as a derivatization reagent, and acrylamide and thiosalicylic acid undergo an electrophilic addition reaction to generate 2-(2-carboxymethylphenylthio) propionamide. Among them, the 2-(2-carboxymethylphenylthio) propionamide generated by derivatization is very easy to separate in high performance liquid chromatography, and can achieve the purpose of separation and detection through high performance liquid chromatography, so it is easy to eliminate the interference of matrix effect and improve the 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] The detection method provided in the embodiment of the present application can more accurately detect the acrylamide content in polyacrylamide, and the detection method is highly efficient; it solves the problem of impurity interference in the existing acrylamide detection method, and has a better application prospect in the quality control of polyacrylamide products.

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

[0039] Figure 1 This is a schematic diagram showing the effect of the derivatization reaction temperature on the acrylamide peak area;

[0040] Figure 2 is the liquid chromatogram of acrylamide;

[0041] Figure 3 Schematic diagram of the linear equation of acrylamide concentration and peak area. DETAILED DESCRIPTION

[0042] The technical scheme in the embodiments will be clearly and completely described below in combination with the embodiments of the present application and the accompanying drawings. Obviously, the embodiments described below are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0043] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations 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, unless the context clearly indicates otherwise, the singular forms of "a", "an" and "the" are intended to include plural forms.

[0045] The following is a detailed description of the method for detecting the acrylamide content in the polyacrylamide of the embodiment of the present application and its application.

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

[0047] In the prior art, when acrylamide is detected by high performance liquid chromatography, since the detection wavelength of acrylamide is relatively short, at about 200 nm, almost all substances respond at this wavelength, and interference is serious when the sample composition is complex; at the same time, acrylamide has good water solubility and a short retention time in most chromatographic columns, so that acrylamide and impurities cannot be separated, affecting the accuracy of the results.

[0048] In view of this, this embodiment provides a method for detecting the acrylamide content in polyacrylamide.

[0049] Specifically, the detection method comprises:

[0050] (1) preparing acrylamide standard solutions of different concentrations; reacting the acrylamide standard solutions of different concentrations with an inorganic acid solution and thiosalicylic acid in a water bath to obtain standard samples of different concentrations;

[0051] (2) performing high performance liquid chromatography ultraviolet detection on standard samples of different concentrations to obtain peak areas of acrylamide in the standard samples of different concentrations; based on the peak areas corresponding to the standard samples of different concentrations, obtaining a linear equation for the corresponding relationship between concentration x and peak area y;

[0052] (3) preparing a polyacrylamide solution, reacting the polyacrylamide solution with an inorganic acid solution and thiosalicylic acid in a water bath to obtain a sample to be tested;

[0053] (4) Performing high performance liquid chromatography ultraviolet detection on the sample to be tested to obtain the peak area of ​​acrylamide in the sample to be tested; substituting the peak area of ​​acrylamide in the sample to be tested into a linear equation to calculate the concentration of acrylamide in the sample to be tested.

[0054] It can be understood that the thiosalicylic acid in this embodiment is added in the form of a thiosalicylic acid solution; in this embodiment, thiosalicylic acid is used as a derivatization reagent, and acrylamide and thiosalicylic acid undergo an electrophilic addition reaction to generate 2-(2-carboxymethylphenylthio)propionamide. Among them, the 2-(2-carboxymethylphenylthio)propionamide 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, so it is easy to eliminate the interference of matrix effect and improve the detection accuracy.

[0055] Therefore, the detection method of this embodiment is not only easy to operate, but also can effectively improve the separation effect, detection accuracy and precision.

[0056] Next, the relevant steps of the above detection method will be further described.

[0057] Step (1), preparing acrylamide standard solutions of different concentrations; reacting the acrylamide standard solutions of different concentrations with inorganic acid solution and thiosalicylic acid in a water bath to obtain standard samples of different concentrations; may be;

[0058] Weigh 0.1025 g of acrylamide standard into a 100 mL volumetric flask and dilute to the mark with distilled water. The concentration is 1025 mg / L. Transfer 10 mL to another 100 mL volumetric flask and dilute to the mark with distilled water as a stock solution (102.5 mg / L).

[0059] After obtaining the stock solution, acrylamide standard solutions of different concentrations can be prepared based on the stock solution, and inorganic acid solution and thiosalicylic acid are added to the acrylamide standard solution, which is placed in a water bath for reaction to obtain standard samples of different concentrations.

[0060] Wherein, acrylamide standard solutions of different concentrations are reacted with inorganic acid solution and thiosalicylic acid in a water bath to obtain standard samples of different concentrations, including:

[0061] Inorganic acid solution and thiosalicylic acid were added to standard acrylamide solutions of different concentrations, and the solutions were placed in a 65°C water bath for reaction;

[0062] After the reaction, acetonitrile was added, the volume was fixed with distilled water, and bubbles were removed by ultrasonic wave. Standard samples of different concentrations were obtained after filtration.

[0063] For example, after obtaining the above-mentioned stock solution, 0.50mL, 1.00mL, 2.00mL, 3.00mL, 4.00mL and 5.00mL of the stock solution are respectively measured in a 50mL volumetric flask, filled up to 10mL with distilled water, 2mL of acetonitrile is added, 0.5mL of 1% mass concentration of thiosalicylic acid is added, 0.1mL of 10% mass concentration of sulfuric acid solution is added dropwise, and the mixture is placed in a water bath at 65°C for 3 hours; after the reaction is completed, 20mL of acetonitrile is added, the volume is adjusted to the scale with distilled water, and bubbles are removed by ultrasonication for 5 minutes; a series of standard samples are obtained by filtering with a syringe filter.

[0064] This example found through relevant experiments that the peak area of ​​acrylamide increases with increasing temperature, and after reaching the peak value, it decreases with increasing temperature. When the temperature is 65°C, the peak area is the largest, and this temperature has a good derivation effect, which is conducive to reflecting the detection results.

[0065] In this embodiment, the preparation method of the thiosalicylic acid solution is as follows: weigh 0.5 g of thiosalicylic acid, add 49.5 g of acetonitrile, and dissolve by ultrasonication to obtain a thiosalicylic acid solution with a mass concentration of 1%.

[0066] In step (1), thiosalicylic acid is used as a derivatization agent in this embodiment, and acrylamide and thiosalicylic acid undergo an electrophilic addition reaction to generate 2-(2-carboxymethylphenylthio)propionamide. The 2-(2-carboxymethylphenylthio)propionamide generated by derivatization is very easy to separate in high performance liquid chromatography, and can achieve the purpose of separation and detection through high performance liquid chromatography, so it is easy to eliminate the interference of matrix effect and improve the detection accuracy and precision.

[0067] In step (2), after the standard samples of different concentrations are prepared, high performance liquid chromatography ultraviolet detection is performed on the standard samples of different concentrations to obtain the peak areas of acrylamide in the standard samples of different concentrations; at the same time, based on the peak areas corresponding to the standard samples of different concentrations, a linear equation of the corresponding relationship between the concentration x and the peak area y is obtained;

[0068] In other words, a linear regression is performed with acrylamide concentration as the abscissa x and the peak area as the ordinate y to obtain the corresponding linear equation.

[0069] Specifically, the above linear equation is: y=100.6292x+3.1635, and the correlation coefficient R 2 =0.99979.

[0070] In step (2), the standard sample after the above derivatization reaction is separated and detected by high performance liquid chromatography ultraviolet; wherein the 2-(2-carboxymethylphenylthio)propionamide 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, so it is easy to eliminate the interference of matrix effect and improve the detection accuracy.

[0071] At the same time, in step (2), based on the above test results (peak area of ​​acrylamide), a linear equation (calibration model) for the corresponding relationship between concentration x and peak area y can be obtained; based on the linear equation, when the content of the sample to be tested is tested, the content (concentration) of acrylamide in the polyacrylamide solution can be quickly obtained according to the peak area of ​​the sample to be tested.

[0072] In step (3), a polyacrylamide solution is prepared, and the polyacrylamide solution is reacted with an inorganic acid solution and thiosalicylic acid in a water bath to obtain a sample to be tested, comprising:

[0073] Prepare a polyacrylamide solution, add an inorganic acid solution and thiosalicylic acid to the polyacrylamide solution respectively, and place the solution in a 65°C water bath for reaction;

[0074] After the reaction is completed, acetonitrile is added, and the test solution is obtained after the volume is fixed with acetonitrile;

[0075] The test solution was filtered and mixed with an equal volume of distilled water, and air bubbles were removed by ultrasound to obtain the test sample.

[0076] Specifically, the above steps may be:

[0077] Weigh 8g (accurate to 1mg) of liquid polyacrylamide, place it in a 100mL beaker, add 2mL of distilled water and 2mL of acetonitrile, add 0.5mL of 1% mass concentration of thiosalicylic acid, drop 0.1mL of 10% mass concentration of sulfuric acid solution, stir evenly with a glass rod, seal with plastic wrap, and place in a water bath at 65℃ for 3 hours. After the reaction is completed, add 20mL of acetonitrile, stir with a glass rod to condense the polyacrylamide, transfer the solution to a 50mL volumetric flask, wash the beaker and polymer (polyacrylamide) with acetonitrile 3-5 times, transfer the washing liquid to a volumetric flask, dilute to the scale with acetonitrile, filter with a syringe filter to obtain a 2mL scale with a scale sample tube, filter the distilled water to the 4m scale, mix well, remove bubbles with ultrasound, and obtain the sample to be tested.

[0078] Usually, the ultrasonication time is 3 to 5 minutes, preferably 5 minutes.

[0079] The liquid polyacrylamide (solution) can be obtained by conventional dissolution methods; for example, 1 g of solid sample polyacrylamide is taken, and 7 mL of distilled water is added to dissolve it to obtain 8 g of liquid polyacrylamide.

[0080] It can be understood that the purpose of step (3) is to allow acrylamide in the polyacrylamide solution to undergo an electrophilic addition reaction with thiosalicylic acid to generate 2-(2-carboxymethylphenylthio)propionamide. The derivatized 2-(2-carboxymethylphenylthio)propionamide is very easy to separate in the subsequent high performance liquid chromatography, which can eliminate the interference of matrix effects and improve the accuracy of the detection results.

[0081] In step (4), the sample to be tested is subjected to high performance liquid chromatography ultraviolet detection to obtain the peak area of ​​acrylamide in the sample to be tested; the peak area of ​​acrylamide in the sample to be tested is substituted into a linear equation to calculate the concentration of acrylamide in the sample to be tested, which specifically includes:

[0082] 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 ​​acrylamide; the obtained peak area of ​​acrylamide is substituted into the linear equation described in step (2) to calculate the concentration of acrylamide.

[0083] Therefore, in this embodiment, the sample to be tested after the derivatization reaction is separated and detected by high performance liquid chromatography ultraviolet, and the peak area of ​​acrylamide 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 acrylamide in the polyacrylamide solution can be quickly obtained according to the peak area of ​​the sample to be tested.

[0084] Therefore, the testing scheme of this embodiment has better detection accuracy, and the testing process is more convenient and faster.

[0085] As an implementation manner, the inorganic acid solution used in this embodiment is preferably a dilute sulfuric acid solution, such as a sulfuric acid solution with a mass concentration of 10%.

[0086] It is understandable that in the test processes in steps (2) and (4), the sample (standard sample or sample to be tested) is injected into a high performance liquid chromatograph for high performance liquid ultraviolet detection.

[0087] As an implementation mode, the chromatographic column used in the above-mentioned high performance liquid chromatography ultraviolet detection is Agilent SB-C8, and the column temperature of the chromatographic column is 30°C.

[0088] As an embodiment, the chromatographic conditions of the above-mentioned high performance liquid chromatography ultraviolet detection include:

[0089] The detection wavelength is 250-260 nm (e.g., 258 nm), and the injection volume is 20 μL;

[0090] Mobile phase A was acetonitrile;

[0091] The mobile phase B is a mixed solution of acetonitrile, water and phosphoric acid (such as phosphoric acid with a mass concentration of 85%) in a volume ratio of 100:898:2.

[0092] In this embodiment, the gradient elution program of mobile phase A and mobile phase B is:

[0093] Elution was performed with mobile phase A and mobile phase B in a volume ratio of 15:85 for 10 min;

[0094] Elution was performed with mobile phase A and mobile phase B in a volume ratio of 80:20 for 5 min;

[0095] Elution was performed with mobile phase A and mobile phase B in a volume ratio of 15:85 for 5 min;

[0096] Among them, the flow rate is 1.0mL / min.

[0097] Therefore, in this embodiment, thiosalicylic acid is used as a derivatization reagent, and acrylamide and thiosalicylic acid undergo an electrophilic addition reaction to generate 2-(2-carboxymethylphenylthio) propionamide. Among them, the 2-(2-carboxymethylphenylthio) propionamide generated by derivatization is very easy to separate in high performance liquid chromatography, and can achieve the purpose of separation and detection through high performance liquid chromatography, so it is easy to eliminate the interference of matrix effect and improve the detection accuracy; in summary, the detection method of this embodiment is not only easy to operate, but also can effectively improve the separation effect, detection accuracy and precision.

[0098] Next, the use of the above detection method in the quality control of polyacrylamide products will be explained.

[0099] It is understandable that since a certain amount of acrylamide will remain in the cationic polyacrylamide produced using acrylamide as a raw material, and cationic polyacrylamide is widely used in water treatment and hair care, the residual acrylamide will be directly or indirectly contacted or ingested by the human body. Therefore, when using acrylamide as a raw material to produce polyacrylamide, the residual amount in the polyacrylamide should be limited.

[0100] As mentioned above, the detection method provided in this embodiment can detect the acrylamide content in polyacrylamide more accurately and quickly, and the detection method is highly efficient; therefore, it can meet the needs of acrylamide safety risk screening in polyacrylamide products, and provide good technical support for the quality control and safety monitoring of polyacrylamide products, suggesting that the detection method has better application prospects in the quality control of polyacrylamide products.

[0101] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate / explain the present application and are not used to limit the scope of the present application.

[0102] In the following examples, the materials, reagents and instruments used can be purchased from commercial sources unless otherwise specified.

[0103] 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:

[0104] The preparation method of the thiosalicylic acid solution is as follows: weigh 0.5 g of thiosalicylic acid, add 49.5 g of acetonitrile, and dissolve by ultrasonication to obtain a thiosalicylic acid solution with a mass concentration of 1%.

[0105] Agilent 1260 liquid chromatograph was used for high performance liquid chromatography, and the concentration of phosphoric acid solution in mobile phase B was 85%.

[0106] Mobile phase A was acetonitrile; mobile phase B was acetonitrile: water: phosphoric acid = 100: 898: 2 (volume ratio).

[0107] The gradient elution program is shown in Table 1 below:

[0108] Table 1:

[0109] Time (min) Mobile phase A(%) Mobile phase B(%) Flow rate (mL / min) 0.00 15 85 1 10.00 15 85 1 11.00 80 20 1 16.00 80 20 1 17.00 15 85 1 22.00 15 85 1

[0110] Among them, the chromatographic column selected is Agilent ZORBAX SB-C8, the chromatographic column length is 250mm, the chromatographic column inner diameter is 4.6mm, and the chromatographic column filler particle diameter is 5μm; the detection wavelength is set to 258 nm, the column temperature is 30℃, and the injection volume is 20μL.

[0111] Embodiment 1-10:

[0112] The present application found that the derivatization temperature of acrylamide affects its peak area. Therefore, the peak area of ​​acrylamide is detected by setting a gradient water bath temperature, specifically:

[0113] Weigh 0.1009 g of acrylamide 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, add distilled water to dilute to volume, mix well, and obtain a stock solution with a concentration of 100.9 mg / L;

[0114] Take 10 50mL volumetric flasks, transfer 4mL of 100.9mg / L acrylamide stock solution into the volumetric flasks respectively, make up to 10mL with distilled water, add 2mL acetonitrile, add 0.5mL 1% mass concentration of thiosalicylic acid, and drop 0.1mL 10% mass concentration of sulfuric acid solution; place in a water bath at 40, 45, 50, 55, 60, 65, 70, 75, 80, 85℃ for 3 hours respectively. After the reaction is completed, add 20mL acetonitrile, distilled water to 50mL, ultrasonic for 5 minutes to remove bubbles, filter into a sample bottle with a syringe filter, inject into a high performance liquid chromatograph for separation and detection, and the test results are shown in Table 2.

[0115] The water bath temperature is the horizontal axis and the peak area is the vertical axis. The test results are as follows: Figure 1 shown.

[0116] Table 2: Water bath temperature and resolution

[0117] Example Water bath temperature (℃) Peak area Example 1 40 100.3 Example 2 45 155.7 Example 3 50 480.8 Example 4 55 753.6 Example 5 60 816.7 Example 6 65 823.4 Example 7 70 819.7 Example 8 75 800.2 Example 9 80 782.4 Example 10 85 750.3

[0118] Based on Table 2 and Figure 1 The test results show that the peak area of ​​acrylamide increases with the increase of temperature. After reaching the peak value, it decreases with the increase of temperature. Among them, when the temperature is 65℃, the peak area is the largest, and the derivatization effect is good at this temperature. Therefore, the derivatization temperature is determined to be 65℃.

[0119] Among them, the liquid chromatogram after separation is as follows Figure 2 As shown. Combined Figure 2 It can be seen from the liquid chromatogram that no interference peak appears in the liquid chromatogram; that is, in this embodiment, thiosalicylic acid is used as a derivatization reagent to eliminate the interference of matrix effects and improve the accuracy of the detection results.

[0120] Accuracy experiment

[0121] Embodiment 11-16:

[0122] Weigh 0.1025 g of acrylamide standard into a 100 mL volumetric flask, dilute to the mark with distilled water, and the concentration is 1025 mg / L; transfer 10 mL to another 100 mL volumetric flask, dilute to the mark with distilled water, and use it as a stock solution (102.5 mg / L) for later use; measure 0.50 mL, 1.00 mL, 2.00 mL, 3.00 mL, 4.00 mL, and 5.00 mL of the stock solution into a 50 mL volumetric flask, fill up to 10 mL with distilled water, and add 2mL acetonitrile, add 0.5mL 1% thiosalicylic acid, add 0.1mL 10% sulfuric acid solution, and place them in a water bath at 65°C for 3 hours; after the reaction, add 20mL acetonitrile, distilled water to the scale, and remove bubbles by ultrasonic for 5 minutes; filter with a syringe filter to obtain a series of standard samples; filter with a syringe filter into a sample bottle, inject into a high performance liquid chromatograph for ultraviolet spectrum detection, and obtain the peak area of ​​acrylamide. The test results are shown in Table 3:

[0123] Table 3: Peak area for detection of acrylamide

[0124] Example Acrylamide(mg / L) Peak area Embodiment 11 1.025 107.17 Example 12 2.050 208.97 Embodiment 13 4.100 417.58 Embodiment 14 6.150 621.17 Embodiment 15 8.200 838.44 Example 16 10.25 1026.32

[0125] Combined with the test results in Table 3, linear regression was performed with acrylamide concentration as the horizontal coordinate and peak area as the vertical coordinate. The linear equation was: y=100.6292x+3.1635, and the correlation coefficient R 2 =0.9979, the linear equation is Figure 3 As shown; combined with Table 3 and Figure 3 The test results show that acrylamide has good linearity in the concentration range of 0-10 mg / L.

[0126] Embodiment 17-19:

[0127] Weigh 3 parts of liquid polyacrylamide accurately, the weight is shown in Table 4 (accurate to 1 mg), place them in a 100mL beaker, add 2mL of distilled water, add 2mL of acetonitrile, add 0.5mL of 1% mass concentration of thiosalicylic acid, add 0.1mL of 10% mass concentration of sulfuric acid solution, stir evenly with a glass rod, seal with food preservative film, and place them in a water bath at 65℃ for 3 hours. After the reaction is completed, add 20mL of acetonitrile, stir with a glass rod to precipitate the polymer, transfer the solution into a 50mL volumetric flask, wash the beaker with acetonitrile, transfer the washing liquid into the volumetric flask and adjust to the scale; filter with a syringe filter to obtain a 2mL scale of a scaled sample tube, then filter the distilled water to the 4mL scale, mix well, and remove bubbles by ultrasonic for 5 minutes to obtain the sample to be tested.

[0128] The obtained samples to be tested were injected into a high performance liquid chromatograph for ultraviolet spectrum detection to obtain the peak area of ​​acrylamide, which was substituted into the linear equations obtained in the above Examples 11-16, respectively, to calculate the content of acrylamide in each sample, that is, the content of the target substance contained in Examples 17-19, recorded as A value.

[0129] Embodiment 20-22:

[0130] Accurately weigh 3 parts of liquid polyacrylamide, the weight is shown in Table 4 (accurate to 1 mg), and place them in 100 mL beakers respectively. Take the stock solution (102.5 mg / L) prepared in Example 11-16 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 2 mL of distilled water, add 2 mL of acetonitrile, add 0.5 mL of 1% mass concentration of thiosalicylic acid, add 0.1 mL of 10% mass concentration of sulfuric acid solution, stir evenly with a glass rod, seal with food preservative film, and place in a water bath at 65°C for 3 hours. After the reaction is completed, 20 mL of acetonitrile is added, stirred with a glass rod to precipitate the polymer, and the solution is transferred to a 50 mL volumetric flask, and then the beaker is washed with acetonitrile, and the washing solution is transferred to a volumetric flask and fixed to the scale, and filtered with a syringe filter to obtain a 2 mL scale of a scaled sample tube, and then distilled water is filtered to the 4 mL scale, mixed, and ultrasonicated for 5 minutes to remove bubbles. Filtered into a sample bottle with a syringe filter, the obtained sample was injected into a high performance liquid chromatograph for ultraviolet spectrum detection, and the peak area of ​​acrylamide was obtained, which was substituted into the linear equation obtained in the above Examples 11-16, and the content of acrylamide in the sample was calculated, that is, the content of the target substance contained in Examples 20-22, recorded as C value.

[0131] The recovery rate was calculated based on the A value and the C value, where the recovery rate was calculated as follows: .

[0132] In the above formula: A is the content of the target substance contained in Examples 17-19; B is the increase in sample concentration after adding the reference substance; C is the content of the target substance contained in Examples 20-22.

[0133] The calculation formula of B value is:

[0134] (Concentration of stock solution*volume of stock solution added) / weight of the corresponding test sample in Examples 20-22.

[0135] Among them, each concentration was prepared in triplicate, and three groups of parallel experiments were performed. The recovery rates were determined respectively under the content determination item. The test results are shown in Table 4 below; among them, the recovery rates in Table 4 were calculated by substituting the average value of the A values ​​(i.e., 30.49 mg / kg) into the above recovery rate calculation formula.

[0136] Table 4: Accuracy test results

[0137]

[0138] According to the test results in Table 4, the average recovery rate of the three parallel group experiments was greater than 96%, and the RSD was less than 3%, indicating that the detection method of this embodiment has excellent accuracy.

[0139] Precision experiment

[0140] Embodiment 23-28:

[0141] The liquid polyacrylamide solution of Example 17 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:

[0142] Table 5: Precision test results

[0143]

[0144] According to the test results in Table 5, it is shown that the detection method of this embodiment has excellent precision and repeatability.

[0145] Solution stability test

[0146] Examples 29-33:

[0147] The liquid polyacrylamide solution of Example 17 was taken and sampled 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:

[0148] Table 6: Solution stability test results

[0149]

[0150] 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.

[0151] In summary, in this embodiment, thiosalicylic acid is used as a derivatization reagent, and acrylamide and thiosalicylic acid undergo an electrophilic addition reaction to generate 2-(2-carboxymethylphenylthio) propionamide. Among them, the 2-(2-carboxymethylphenylthio) propionamide generated by derivatization is very easy to separate in high performance liquid chromatography, and can achieve the purpose of separation and detection through high performance liquid chromatography, so it is easy to eliminate the interference of matrix effect and improve the detection accuracy; therefore, the detection method of this embodiment is not only easy to operate, but also can effectively improve the separation effect, detection accuracy and precision.

[0152] The technical solutions provided in the embodiments of the present application are introduced in detail above. 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 will be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present application.

Claims

1. A method for detecting acrylamide content in polyacrylamide, characterized in that: The detection method comprises: Prepare acrylamide standard solutions of different concentrations; react the acrylamide standard solutions of different concentrations with an inorganic acid solution and thiosalicylic acid in a water bath to obtain standard samples of different concentrations; wherein the acrylamide and thiosalicylic acid undergo an electrophilic addition reaction; Performing high performance liquid chromatography ultraviolet detection on standard samples of different concentrations to obtain the peak areas of acrylamide in the standard samples of different concentrations; obtaining a linear equation of 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 polyacrylamide solution, add an inorganic acid solution and thiosalicylic acid to the polyacrylamide solution respectively, and place the solution in a 65°C water bath for reaction; add acetonitrile after the reaction is completed, and obtain a test solution after constant volume with acetonitrile; filter the test solution, mix it with an equal volume of distilled water, and remove bubbles with ultrasound to obtain a test sample; Performing high performance liquid chromatography ultraviolet detection on the sample to be tested to obtain the peak area of ​​acrylamide in the sample to be tested; substituting the peak area of ​​acrylamide in the sample to be tested into a linear equation to calculate the concentration of acrylamide in the sample to be tested; Wherein, the chromatographic column used in the high performance liquid chromatography ultraviolet detection is Agilent SB-C8; The chromatographic conditions of the high performance liquid chromatography ultraviolet detection include: The detection wavelength is 250~260nm; 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 the mobile phase A and the mobile phase B is: Elution was performed with mobile phase A and mobile phase B in a volume ratio of 15:85 for 10 min; Elution was performed with mobile phase A and mobile phase B in a volume ratio of 80:20 for 5 min; Elution was performed with mobile phase A and mobile phase B in a volume ratio of 15:85 for 5 min.

2. The detection method according to claim 1, characterized in that: The acrylamide standard solutions of different concentrations are reacted with the inorganic acid solution and thiosalicylic acid in a water bath to obtain standard samples of different concentrations, including: Inorganic acid solution and thiosalicylic acid were added to standard acrylamide solutions of different concentrations, and the solutions were placed in a 65°C water bath for reaction; After the reaction, acetonitrile was added, the volume was fixed with distilled water, and bubbles were removed by ultrasonic wave. Standard samples of different concentrations were obtained after filtration.

3. The detection method according to claim 1 or 2, characterized in that: The inorganic acid solution is a dilute sulfuric acid solution.

4. The detection method according to claim 1, characterized in that: The linear equation is: y=100.6292x+3.1635, correlation coefficient R 2 =0.99979.

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

6. The detection method according to claim 1, characterized in that: The injection volume of the high performance liquid chromatography ultraviolet detection is 20 μL.

7. The detection method according to claim 1, characterized in that: In the gradient elution program of mobile phase A and mobile phase B, the flow rate was 1.0 mL / min.

8. Use of the detection method according to any one of claims 1 to 7 in the quality control of polyacrylamide products.

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