Determination method of active ingredient content in polyamide epichlorohydrin wet strength agent

Abstract

The present invention provides a method for detecting the content of effective components in a polyamide epichlorohydrin wet strength agent, and belongs to the technical field of analysis and detection. The detection method comprises the following steps: (1) preparing a PAE test solution; (2) obtaining a reaction solution 1 through an acid hydrolysis reaction; (3) obtaining a reaction solution 2 through an esterification reaction; (4) using a gas chromatograph-mass spectrometer to test the response value of diethyl adipate in the sample to be tested; (5) drawing a standard curve to calculate the concentration of diethyl adipate in the sample to be tested; (6) excluding the concentrations of diethyl adipate and adipic acid in the test sample; (7) calculating the content of effective components in the polyamide epichlorohydrin wet strength agent sample to be tested by a formula. The method is used for detecting the content of effective components in a polyamide epichlorohydrin wet strength agent, can accurately calculate the content of PAE effective components in the wet strength agent, significantly improves the accuracy and reliability of the determination, reduces the detection cost and operation difficulty, and has wide applicability.

Description

Technical Field

[0001] The invention belongs to the technical field of analysis and detection, and in particular relates to a method for detecting the content of effective components in a polyamide epichlorohydrin wet strength agent. Background Art

[0002] In the modern papermaking industry, polyamide epichlorohydrin (PAE) wet strength agent is widely used to improve the wet and dry strength of paper. Accurately determining the content of active ingredients in PAE wet strength agent is of great significance for ensuring product quality, maintaining fair competition in the market, and enhancing brand reputation. At present, the existing detection technologies for the content of PAE active ingredients mainly include drying method and nuclear magnetic resonance method.

[0003] The drying method mainly calculates the remaining solid content by placing a certain amount of wet strength agent sample in an oven at 105°C to evaporate water and other volatile substances. This method is simple to operate and easy to perform, and is widely used in laboratory testing. However, the inherent disadvantage of the drying method is that it cannot distinguish the actual effective ingredients in the sample from adulterated substances (such as industrial salt, urea and sodium sulfate, etc.) based only on weight changes, which may cause distortion of the test results.

[0004] Nuclear magnetic resonance (NMR) can provide high detection accuracy by detecting the magnetic resonance signal of hydrogen atoms in the sample, and can perform detailed molecular structure analysis of the PAE component in the wet strength agent. Although the NMR method can accurately determine the PAE content in theory, its equipment is expensive, the operation is complicated, and the experimental conditions are strict, making it unsuitable for routine testing. Summary of the invention

[0005] The invention aims to solve the problems of insufficient accuracy and high cost in detecting the content of PAE active ingredient in wet strength agent by existing drying method and nuclear magnetic resonance method.

[0006] The present invention provides a method for detecting the content of an effective ingredient in a polyamide epichlorohydrin wet strength agent, comprising the following steps:

[0007] (1) Dilute the polyamide epichlorohydrin wet strength agent to be tested with water to obtain a PAE test solution;

[0008] (2) After adding concentrated hydrochloric acid and the PAE test solution obtained in step (1) into a conical flask, a condenser is installed in the conical flask, and after heating and refluxing the reaction, the reaction solution is transferred to an evaporator bottle to evaporate the solvent, thereby obtaining a reaction solution 1;

[0009] (3) adding anhydrous ethanol, concentrated sulfuric acid and toluene to the evaporator bottle containing the reaction solution 1, mixing, ultrasonicating the evaporator bottle, and placing it in a water bath for heating and reaction to obtain the reaction solution 2;

[0010] (4) transferring the reaction solution obtained in step (3) into a nitrogen blowpipe, rinsing, and concentrating the solution by nitrogen blowpipe; fixing the volume with a solvent, extracting, taking the upper layer of liquid and diluting it, and testing it on a gas chromatograph-mass spectrometer to obtain the response value of diethyl adipate of the sample to be tested;

[0011] (5) preparing standard working solutions of diethyl adipate of different concentrations to obtain standard working solution samples; testing on a gas chromatograph mass spectrometer to obtain the response value of diethyl adipate; plotting a standard curve using the response value of diethyl adipate of the obtained standard working solution sample and the corresponding concentration points; and then calculating the concentration of diethyl adipate in the test sample by the external standard method using the response value of diethyl adipate of the test sample in step (4) and the standard curve obtained above, and recording it as C ;

[0012] (6) Take the PAE test solution obtained in step (1), add solvent to make up the volume, extract, take the upper liquid, and directly detect the concentration of diethyl adipate using a gas chromatograph-mass spectrometer to obtain the concentration of diethyl adipate, which is recorded as C 0 ;

[0013] Take the PAE test solution obtained in step (1) and directly detect the concentration of adipic acid using a liquid chromatograph to obtain the concentration of adipic acid, which is recorded as C 1 ;

[0014] (7) Calculation of results

[0015] Calculate the effective ingredient content of the polyamide epichlorohydrin wet strength agent sample to be tested according to formula (1);

[0016] (1)

[0017] Where:

[0018] E ——The content of active ingredients in the sample to be tested, %;

[0019] m ——The mass of the sample to be tested, g;

[0020] C ——The concentration of diethyl adipate measured after hydrolysis and esterification of the sample, μg / L;

[0021] V ——The volume of solvent required for final volume adjustment after sample hydrolysis and esterification, mL;

[0022] f ——The final dilution factor of the sample after hydrolysis and esterification;

[0023] C 0——The concentration of diethyl adipate directly measured without hydrolysis and esterification of the sample, μg / L;

[0024] V 0 ——The volume of solvent required for final volume determination when the sample is not hydrolyzed and esterified to test the concentration of diethyl adipate, mL;

[0025] f 0 ——The final dilution factor of the sample when testing the diethyl adipate concentration without hydrolysis and esterification;

[0026] C 1 ——The concentration of adipic acid directly measured without hydrolysis and esterification of the sample, mg / L;

[0027] V 1 ——The volume of the sample before hydrolysis and esterification to test the adipic acid concentration, mL;

[0028] f 1 ——The final dilution factor of the sample when testing the adipic acid concentration without hydrolysis and esterification.

[0029] Furthermore, in step (1), the usage ratio of polyamide epichlorohydrin wet strength agent and water is 0.1-0.5 g:100 mL;

[0030] In step (2), the ratio of the PAE test solution obtained in step (1) to concentrated hydrochloric acid is 20.0 mL: (10.0-50.0) mL.

[0031] Furthermore, in step (1), the ratio of the polyamide epichlorohydrin wet strength agent to water is 0.1 g: 100 mL;

[0032] In step (2), the ratio of the PAE test solution obtained in step (1) to concentrated hydrochloric acid is 20.0 mL:40.0 mL.

[0033] Furthermore, in step (2), the heating reflux reaction time is 1.5 to 3 hours; the heating reflux reaction temperature is 250 to 300°C.

[0034] Furthermore, in step (2), the heating reflux reaction time is 2 hours; and the heating reflux reaction temperature is 275°C.

[0035] Furthermore, in step (3), the ratio of the reaction solution 1, anhydrous ethanol, and concentrated sulfuric acid is 1-5 mL: 20 mL: 1-2 mL;

[0036] In step (3), the usage ratio of toluene to anhydrous ethanol is 10-30 mL:20 mL.

[0037] Furthermore, in step (2), the reaction liquid is transferred to an evaporator bottle to evaporate the solvent, specifically: the reaction liquid is transferred to an evaporator bottle of a vacuum parallel concentrator, and evaporated by the vacuum parallel concentrator until the liquid volume remains 1-5 mL;

[0038] In step (2), when evaporation is performed using a vacuum parallel concentrator, the water bath temperature is 40-60°C, the rotation speed is 140-160 rpm, and the vacuum degree is 10-30 mbar;

[0039] In step (3), the mixing is carried out by shaking; the shaking time is 5 to 15 minutes; the shaking speed is 150 rpm; the vacuum degree during shaking is normal pressure;

[0040] In step (3), the ultrasonic time of the evaporator bottle is 5 to 20 minutes; during the ultrasonication, the water temperature in the ultrasonicator is 40°C to 50°C;

[0041] In step (3), the temperature of the heating reaction in the water bath is 50-80° C.; and the time of the heating reaction in the water bath is 20-40 min.

[0042] Furthermore, in step (4), rinsing is specifically performed by ethanol rinsing; nitrogen blowing and concentration is specifically performed by nitrogen blowing and concentration at 40-60°C to 2-5 mL; and the extraction time is 1-5 min;

[0043] Furthermore, in step (4) and step (6), the solvent is selected from toluene, ethyl acetate, benzene or dichloromethane.

[0044] Furthermore, in step (6), when testing the concentration of diethyl adipate, the solvent used for volume determination is the same as the solvent used for volume determination in step (4); and the parameters of the gas chromatograph-mass spectrometer are the same as the parameters of the gas chromatograph-mass spectrometer in step (4).

[0045] The present invention has the following advantages:

[0046] 1. High detection accuracy

[0047] The method of the present invention uses a gas chromatography-mass spectrometer (GC-MS) to fully hydrolyze PAE into adipic acid and then esterify it into diethyl adipate for quantitative analysis, so as to accurately measure the effective ingredient content of PAE. Compared with the traditional drying method, this method effectively avoids the problem of distortion of test results caused by adulterated ingredients.

[0048] 2. Strong reliability and repeatability

[0049] The method of the present invention ensures high reliability and repeatability of the detection process by optimizing the experimental steps and conditions (such as acid-water ratio, heating reflux reaction time, reaction temperature, esterification reaction temperature, etc.), and can stably obtain consistent detection results.

[0050] 3. Easy operation and low cost

[0051] The method of the present invention is relatively simple, and the required equipment such as gas chromatography-mass spectrometer (GC-MS) and ultrasonic cleaner are commonly found in most laboratories, which significantly reduces the detection cost and operation difficulty.

[0052] 4. Wide applicability

[0053] The method of the present invention is not only suitable for detecting the effective components of PAE wet strength agent, but also can be used for determining the PAE content in media such as paper and papermaking white water, and can achieve comprehensive monitoring of the PAE content in the entire production process. DETAILED DESCRIPTION

[0054] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0055] The embodiment of the present invention provides a method for detecting the content of an effective ingredient in a polyamide epichlorohydrin wet strength agent, comprising the following steps:

[0056] (1) Dilute the polyamide epichlorohydrin wet strength agent (PAE) to be tested with water to obtain a PAE test solution;

[0057] (2) After adding concentrated hydrochloric acid and the PAE test solution obtained in step (1) into a conical flask, a condenser is installed in the conical flask, and after heating and refluxing the reaction, the reaction solution is transferred to an evaporator bottle to evaporate the solvent, thereby obtaining a reaction solution 1;

[0058] (3) adding anhydrous ethanol, concentrated sulfuric acid and toluene to the evaporator bottle containing the reaction solution 1, mixing, ultrasonicating the evaporator bottle, and placing it in a water bath for heating and reaction to obtain the reaction solution 2;

[0059] (4) transferring the reaction solution obtained in step (3) into a nitrogen blowpipe, rinsing, and concentrating the solution by nitrogen blowpipe; fixing the volume with a solvent, extracting, taking the upper layer of liquid and diluting it, and testing it on a gas chromatograph-mass spectrometer to obtain the response value of diethyl adipate of the sample to be tested;

[0060] (5) preparing standard working solutions of diethyl adipate of different concentrations to obtain standard working solution samples; testing on a gas chromatograph mass spectrometer to obtain the response value of diethyl adipate; plotting a standard curve using the response value of diethyl adipate of the obtained standard working solution sample and the corresponding concentration points; and then calculating the concentration of diethyl adipate in the test sample by the external standard method using the response value of diethyl adipate of the test sample in step (4) and the standard curve obtained above, and recording it asC ;

[0061] (6) Take the PAE test solution obtained in step (1), add solvent to make up the volume, extract, take the upper liquid, and directly detect the concentration of diethyl adipate using a gas chromatograph-mass spectrometer to obtain the concentration of diethyl adipate, which is recorded as C 0 ;

[0062] Take the PAE test solution obtained in step (1) and directly detect the concentration of adipic acid using a liquid chromatograph to obtain the concentration of adipic acid, which is recorded as C 1 ;

[0063] (7) Calculation of results

[0064] Calculate the effective ingredient content of the PAE wet strength agent sample according to formula (1);

[0065] (1)

[0066] Where:

[0067] E ——The content of active ingredients in the sample to be tested, %;

[0068] m ——The mass of the sample to be tested, g;

[0069] C ——The concentration of diethyl adipate measured after hydrolysis and esterification of the sample, μg / L;

[0070] V ——The volume of solvent required for final volume adjustment after sample hydrolysis and esterification, mL;

[0071] f ——The final dilution factor of the sample after hydrolysis and esterification;

[0072] C 0 ——The concentration of diethyl adipate directly measured without hydrolysis and esterification of the sample, μg / L;

[0073] V 0 ——The volume of solvent required for final volume determination when the sample is not hydrolyzed and esterified to test the concentration of diethyl adipate, mL;

[0074] f 0 ——The final dilution factor of the sample when testing the diethyl adipate concentration without hydrolysis and esterification;

[0075] C 1——The concentration of adipic acid directly measured without hydrolysis and esterification of the sample, mg / L;

[0076] V 1 ——The volume of the sample before hydrolysis and esterification to test the adipic acid concentration, mL;

[0077] f 1 ——The final dilution factor of the sample when testing the adipic acid concentration without hydrolysis and esterification.

[0078] Polyamide epichlorohydrin (PAE) wet strength agent is used to improve the wet and dry strength of paper. Its active ingredient is mainly polyamide epichlorohydrin (PAE), and it often contains doping substances (such as industrial salt, urea, sodium sulfate, etc.), which affect the product quality and effect of the wet strength agent. The embodiment of the present invention proposes a scientific, efficient and accurate detection method, which hydrolyzes the active ingredient in the polyamide epichlorohydrin wet strength agent to generate adipic acid, then esterifies it to diethyl adipate, and uses gas chromatography-mass spectrometry (GC-MS) for quantitative analysis. This method can accurately calculate the content of the PAE active ingredient in the wet strength agent through an equimolar relationship, significantly improves the accuracy and reliability of the determination, reduces the detection cost and operation difficulty, and has wide applicability.

[0079] .

[0080] In one embodiment of the present invention, in step (1), the usage ratio of polyamide epichlorohydrin wet strength agent to water is 0.1-0.5 g:100 mL. For example, the usage ratio of polyamide epichlorohydrin wet strength agent to water can be 0.1 g:100 mL, 0.2 g:100 mL, 0.3 g:100 mL, 0.4 g:100 mL, 0.5 g:100 mL.

[0081] In a preferred embodiment of the present invention, in step (1), the usage ratio of polyamide epichlorohydrin wet strength agent to water is 0.1 g:100 mL.

[0082] In an embodiment of the present invention, step (2) performs an acid hydrolysis reaction on the PAE test solution. The PAE test solution is mixed with concentrated hydrochloric acid and then heated under reflux conditions to ensure that the amide bonds in the PAE molecular structure are fully cleaved. By heating and reflux, the reaction mixture can be maintained at a boiling point, so that the acid and the PAE molecules are fully in contact, promoting the complete reaction. Subsequently, the reaction solution is transferred to an evaporator bottle for solvent evaporation, which helps to remove excess reaction medium.

[0083] In one embodiment of the present invention, in step (2), the ratio of the amount of the PAE test solution obtained in step (1) to the concentrated hydrochloric acid is 20.0 mL: (10.0-50.0) mL. In a preferred embodiment of the present invention, the ratio of the amount of the PAE test solution obtained in step (1) to the concentrated hydrochloric acid is 20.0 mL: 40.0 mL. Specifically, the mass percentage concentration of the concentrated hydrochloric acid is 36-38%. In the embodiment of the present invention, a suitable acid-water ratio can make the acid hydrolysis reaction more complete, which is more helpful to improve the detection accuracy. A lower acid-water ratio generally leads to incomplete hydrolysis reaction.

[0084] In one embodiment of the present invention, in step (2), the heating reflux reaction time is 1.5 to 3 hours. In a preferred embodiment of the present invention, the heating reflux reaction time is 2 hours. In the embodiment of the present invention, a moderate reflux time provides the best detection effect at a suitable hydrolysis temperature, and a too long reflux time may lead to the occurrence of side reactions.

[0085] In one embodiment of the present invention, in step (2), the temperature of the heating reflux reaction is 250-300° C. In a preferred embodiment of the present invention, the temperature of the heating reflux reaction is 275° C. In the embodiment of the present invention, the appropriate hydrolysis temperature helps to completely hydrolyze PAE and produce a higher content of active ingredients.

[0086] Specifically, in step (2), before heating and reflux reaction, zeolite is added to the conical flask to prevent boiling during the reaction. For example, 6 zeolites can be added to a 250 mL conical flask.

[0087] Specifically, step (2) further comprises, after the heating reflux reaction, rinsing the conical flask and the condenser with water, and pouring the rinsing liquid into the evaporator bottle. For example, 20 mL of first-grade water is used to rinse the conical flask and the condenser three times, and the rinsing liquid is poured into the evaporator bottle.

[0088] Specifically, in step (2), the reaction liquid is transferred to an evaporator bottle to evaporate the solvent, specifically: the reaction liquid is transferred to an evaporator bottle of a vacuum parallel concentrator, and evaporated by the vacuum parallel concentrator until the liquid volume remains 1-5 mL. For example, it can be 1 mL, 2 mL, 3 mL, 4 mL, 5 mL, etc.

[0089] Specifically, in step (2), when evaporation is performed using a vacuum parallel concentrator, the water bath temperature is 40-60°C, the rotation speed is 140-160 rpm, and the vacuum degree is 10-30 mbar. Preferably, when evaporation is performed using a vacuum parallel concentrator, the water bath temperature is 40-60°C, the rotation speed is 150 rpm, and the vacuum degree is 20 mbar.

[0090] In an embodiment of the present invention, step (3) performs an esterification reaction on the reaction solution 1 obtained by acid hydrolysis. Anhydrous ethanol is used as an alcohol source for the esterification reaction, and performs an esterification reaction with the carboxylic acid or its precursor in the reaction solution to generate an ester compound. Concentrated sulfuric acid is used as a catalyst for the esterification reaction. Shaking and ultrasonic treatment help to accelerate the uniform distribution of the substances, so that the reactants are fully contacted and the reaction rate is increased. Subsequently, heating in a water bath can maintain the temperature of the reaction solution within the optimal range, ensuring that the esterification reaction is fully carried out, thereby obtaining a reaction solution 2.

[0091] In one embodiment of the present invention, in step (3), the ratio of the amount of reaction solution 1, anhydrous ethanol, and concentrated sulfuric acid is 1-5 mL: 20 mL: 1-2 mL. Specifically, the mass fraction of concentrated sulfuric acid is 98.3%.

[0092] In one embodiment of the present invention, in step (3), the amount ratio of toluene to anhydrous ethanol is 10-30 mL: 20 mL. Preferably, the amount ratio of toluene to anhydrous ethanol is 20 mL: 20 mL. In the embodiment of the present invention, toluene is used as a solvent to dissolve the reaction product and maintain the uniformity of the reaction environment. At the same time, the high boiling point of toluene helps to maintain a stable temperature of the reaction system during the heating process.

[0093] In one embodiment of the present invention, in step (3), the mixing can be performed by shaking. The shaking time is 5 to 15 minutes. The shaking speed is 150 rpm. The vacuum degree during shaking is normal pressure.

[0094] In one embodiment of the present invention, in step (3), the ultrasonic time of the evaporator bottle is 5 to 20 minutes. More preferably, the ultrasonic time of the evaporator bottle is 10 minutes. During the ultrasonication, the water temperature in the ultrasonicator is about 40°C to 50°C.

[0095] In one embodiment of the present invention, in step (3), the temperature of the heating reaction in the water bath is 50-80°C. The time of the heating reaction in the water bath is 20-40 minutes. For example, the heating reaction in the water bath can be specifically maintained at 50-80°C for 30 minutes. In the embodiment of the present invention, the appropriate esterification reaction temperature can avoid the occurrence of side reactions and improve the detection accuracy, while too high a temperature (90°C) will affect the final detection result.

[0096] In the embodiment of the present invention, in step (4), the polyamide epichlorohydrin wet strength agent after acid hydrolysis and esterification is subjected to gas chromatography-mass spectrometry detection. The obtained reaction solution is concentrated by nitrogen blowing, the solvent is fixed to volume, and the extract is vortexed to obtain the extract, which is then diluted and tested on a gas chromatography-mass spectrometer to obtain the response value of diethyl adipate.

[0097] In one embodiment of the present invention, in step (4), rinsing is specifically rinsing with ethanol. More specifically, 10 mL of ethanol is used to rinse the evaporator bottle three times.

[0098] In one embodiment of the present invention, in step (4), nitrogen blowing and concentration is specifically nitrogen blowing and concentration at 40-60° C. to 2-5 mL.

[0099] In one embodiment of the present invention, in step (4), the extraction time is 1-5 min. For example, it can be 1 min, 2 min, 3 min, 4 min or 5 min.

[0100] In one embodiment of the present invention, in step (4), the extraction method can be vortex or the like.

[0101] In one embodiment of the present invention, in step (4), the solvent is selected from toluene, ethyl acetate, benzene or dichloromethane.

[0102] In one embodiment of the present invention, in step (4), the parameters of the gas chromatograph mass spectrometer are as follows:

[0103] a) Chromatographic column: HP-5MS capillary column (30 mm×0.25 mm×0.25 μm);

[0104] b) Inlet temperature: 250°C;

[0105] c) Split mode: 25:1;

[0106] d) Injection volume: 1 μL;

[0107] e) Heating program: 100°C for 1 min, then increase to 180°C at a rate of 4°C / min, hold for 4 min, then 220°C for 1 min;

[0108] f) Carrier gas: helium;

[0109] g) Constant flow mode: flow rate is 1.0 mL / min;

[0110] h) Mass spectrometry scanning mode: selected ion monitoring;

[0111] i) Ion source: EI;

[0112] j) Temperature: 230°C;

[0113] k) Quadrupole temperature: 150°C.

[0114] In the embodiment of the present invention, step (5) is to calculate the concentration of diethyl adipate in the test sample by drawing a standard curve of diethyl adipate.

[0115] In the embodiment of the present invention, step (6) is a sample matrix interference elimination experiment. By combining a liquid chromatograph and a gas chromatograph-mass spectrometer, the contents of adipic acid and diethyl adipate in the PAE wet strength agent sample are accurately determined, and the accuracy and reliability of the test results are ensured by eliminating the adipic acid and diethyl adipate already present in the sample matrix.

[0116] In one embodiment of the present invention, in step (6), when testing the concentration of diethyl adipate, the solvent used for volume determination can be the same as the solvent used for volume determination in step (4). At this time, the parameters of the gas chromatograph mass spectrometer in step (6) are the same as the parameters of the gas chromatograph mass spectrometer in step (4). Specifically, in step (4) and step (6), the solvent is selected from toluene, ethyl acetate, benzene or dichloromethane.

[0117] In another embodiment of the present invention, in step (6), when testing the concentration of diethyl adipate, the solvent used for volume determination may be different from the solvent used for volume determination in step (4). In this case, the standard curve of diethyl adipate needs to be redrawn, and the parameters of the gas chromatograph mass spectrometer need to be adjusted accordingly.

[0118] In one embodiment of the present invention, in step (6), the extraction time is 1-10 min. The extraction method can be vortex or the like.

[0119] In one embodiment of the present invention, in step (6), when testing the concentration of adipic acid, specifically: preparing standard working solutions of adipic acid of different concentrations to obtain standard working solution samples of adipic acid; testing on a liquid chromatograph to obtain a response value of adipic acid; drawing a standard curve of adipic acid based on the response value of adipic acid of the standard working solution sample and the corresponding concentration point; and then testing the sample to be tested, i.e., the PAE test solution obtained in step (1), on a liquid chromatograph by an external standard method (test parameters are the same as those of the standard working solution sample of adipic acid), using the response value of adipic acid of the sample to be tested and according to the above-mentioned standard curve of adipic acid, calculating the concentration of adipic acid in the sample to be tested, which is recorded as C 1 .

[0120] In one embodiment of the present invention, in step (6), the parameters of the liquid chromatograph are as follows:

[0121] a) Chromatographic column: C18 chromatographic column;

[0122] b) Column temperature: 30°C;

[0123] c) Detection wavelength: 210nm;

[0124] d) Injection volume: 20 μL;

[0125] e) Mobile phase: A:B=80:20, A is 10 mmol / L phosphate buffer solution (pH=2.6), B is methanol;

[0126] f) Flow rate: 1.0 mL / min.

[0127] In the embodiment of the present invention, step (7) is calculated by a specific formula to obtain the effective ingredient content of the PAE wet strength agent.

[0128] It should be pointed out that in the formula, f, f 0 、f 1 The dilution multiples are all the final dilution multiples of the samples. In the detection method of the embodiment of the present invention, step (2) is a hydrolysis reaction, step (3) is an esterification reaction, and step (6) is an exclusion experiment for excluding diethyl adipate and adipic acid in the sample. C, V, f These are the relevant parameters of the sample of the present invention after the hydrolysis reaction in step (2) and the esterification reaction in step (3). C 0 、V 0 、f 0 The parameter related to diethyl adipate when the sample has not undergone step (2) hydrolysis reaction and step (3) esterification reaction. C 1 、V 1 、f 1 It is a parameter related to adipic acid when the sample has not undergone step (2) hydrolysis reaction and step (3) esterification reaction.

[0129] The present invention will be described in detail below with reference to embodiments.

[0130] Example 1 A method for detecting the content of active ingredients in a PAE wet strength agent (sample A) comprises the following steps:

[0131] (1) Weigh 0.1 g of PAE wet strength agent (sample A) and dilute it to 100 mL with water to obtain PAE test solution;

[0132] (2) Take 20.0mL of the diluted PAE test solution obtained in step (1) and add it to a 250mL conical flask. Add 6 zeolites and 40.0mL of concentrated hydrochloric acid (i.e., the acid-water ratio is 40.0mL:20.0mL=2:1). Add a condenser to the conical flask and reflux the reaction on the heating plate at 275°C for 2h. After completion, transfer the liquid to the evaporator bottle and rinse the conical flask and condenser with 20mL of first-grade water three times. Pour the rinse liquid into the evaporator bottle. Evaporate in a vacuum parallel concentrator at a water bath temperature of 60°C, a rotation speed of 150rpm, and a vacuum degree of 20mbar until the liquid volume remains about 2mL;

[0133] (3) Add 20 mL of toluene, 20 mL of anhydrous ethanol and 1 mL of concentrated sulfuric acid to the 2 mL of remaining liquid, and continue to shake the mixed solution at 150 rpm (vacuum is normal pressure) for 10 min. Ultrasonicate the evaporator bottle for 10 min, and the water temperature in the ultrasonicator is about 40°C~50°C. Place the ultrasonicated evaporator bottle in a water bath at 70°C for 30 min, then transfer the solution in the evaporator bottle into a suitable nitrogen blowpipe, and rinse the evaporator bottle with 10 mL of ethanol three times, and concentrate it to about 5 mL at 50°C nitrogen blowpipe;

[0134] (4) Add toluene to make the volume 25mL (the volume of toluene added V 20 mL), vortex extraction for 1 min, take the upper liquid and dilute 100 times. Since step (2) is to take 20 ml from 100 mL, it is equivalent to diluting 5 times, so the final dilution factor is f =100×5=500, and the response value of diethyl adipate of the sample to be tested is obtained by using a gas chromatograph mass spectrometer for testing;

[0135] Among them, the gas chromatography-mass spectrometer parameters are as follows:

[0136] l) Chromatographic column: HP-5MS capillary column (30 mm×0.25 mm×0.25 μm);

[0137] m) Inlet temperature: 250°C;

[0138] n) Split mode: 25:1;

[0139] o) Injection volume: 1 μL;

[0140] p) Heating program: 100℃ for 1 min, then increase to 180℃ at a rate of 4℃ / min, hold for 4 min, then run at 220℃ for 1 min;

[0141] q) Carrier gas: helium;

[0142] r) Constant flow mode: flow rate is 1.0 mL / min;

[0143] s) Mass spectrometry scanning mode: selected ion monitoring;

[0144] t) Ion source: EI;

[0145] u) Temperature: 230°C;

[0146] v) Quadrupole temperature: 150°C.

[0147] (5) preparing standard working solutions of diethyl adipate of different concentrations to obtain standard working solution samples; using a gas chromatograph-mass spectrometer for testing, with the test parameters being the same as the test parameters of the gas chromatograph-mass spectrometer in step (4) to obtain the response value of diethyl adipate; drawing a standard curve using the response value of diethyl adipate of the obtained standard working solution sample and the corresponding concentration points; and then calculating the concentration of diethyl adipate in the test sample by the external standard method using the response value of diethyl adipate of the test sample in step (4) and the standard curve obtained above, which is recorded as C ;

[0148] The concentration of diethyl adipate mother liquor is 50 mg / mL. Take 0.01 mL of mother liquor and add 99.9 mL of toluene to prepare an intermediate solution with a concentration of 5 mg / L.

[0149]

[0150] The standard curve of diethyl adipate is as follows:

[0151] Y=41.046X+2896.670, where Y is the response value of diethyl adipate and X is the concentration of diethyl adipate.

[0152] (6) Take 1.0 mL of the 100 mL PAE solution prepared in step (1) and add toluene. V 0 = 5mL fixed volume, extraction, dilution multiple at this time f 0 =100, take the upper layer of liquid, and use a gas chromatograph-mass spectrometer (with the same instrument parameters as step 4) to detect the response value of diethyl adipate that has not undergone hydrolysis, and then substitute it into the standard curve obtained in step (5), and the concentration of diethyl adipate is recorded as C 0 ;

[0153] Prepare standard working solutions of adipic acid of different concentrations to obtain standard working solution samples; use a liquid chromatograph to test and obtain the response value of adipic acid; draw a standard curve based on the response value of adipic acid of the obtained standard working solution sample and the corresponding concentration point. Then, by using the external standard method, use the response value of adipic acid of the sample to be tested and the above obtained standard curve to calculate the concentration of adipic acid in the sample to be tested; specifically, take 1.0 mL from the 100 mL PAE test solution prepared in step (1), that is, V 1 =1mL, the dilution factor is f 1 =100, and the response value of adipic acid is obtained by liquid chromatography. The concentration of adipic acid in the test sample is calculated according to the standard curve and recorded as C 1 .

[0154] Among them, the parameters of the above-mentioned liquid chromatograph are as follows:

[0155] a) Chromatographic column: C18 chromatographic column;

[0156] b) Column temperature: 30°C;

[0157] c) Detection wavelength: 210nm;

[0158] d) Injection volume: 20 μL;

[0159] e) Mobile phase: A:B=80:20, A is 10 mmol / L phosphate buffer solution (pH=2.6), B is methanol;

[0160] f) Flow rate: 1.0 mL / min.

[0161] (7) Calculation of results

[0162] Based on the equimolar relationship, the active ingredient content of PAE wet strength agent is calculated according to formula (1).

[0163] (1)

[0164] Where:

[0165] E ——The content of active ingredients in the sample to be tested, %;

[0166] m ——The mass of the sample to be tested, g;

[0167] C ——The concentration of diethyl adipate measured after hydrolysis and esterification of the sample, μg / L;

[0168] V——The volume of solvent required for final volume adjustment after sample hydrolysis and esterification, mL;

[0169] f ——The final dilution factor of the sample after hydrolysis and esterification;

[0170] C 0 ——The concentration of diethyl adipate directly measured without hydrolysis and esterification of the sample, μg / L;

[0171] V 0 ——The volume of solvent required for final volume determination when the sample is not hydrolyzed and esterified to test the concentration of diethyl adipate, mL;

[0172] f 0 ——The final dilution factor of the sample when testing the diethyl adipate concentration without hydrolysis and esterification;

[0173] C 1 ——The concentration of adipic acid directly measured without hydrolysis and esterification of the sample, mg / L;

[0174] V 1 ——The volume of the sample before hydrolysis and esterification to test the adipic acid concentration, mL;

[0175] f 1 ——The final dilution factor of the sample when testing the adipic acid concentration without hydrolysis and esterification.

[0176] Sampling volume of sample A m is 0.1060g (accurate to 0.0001g), V =20mL, f =500; f 0 =100, V 0 =5mL; f 1 =100, V 1 =1mL; measured C =671.15μg / L, C 0 =0.0μg / L, C 1 =0.0mg / L, and the PAE active ingredient content is calculated according to formula (1): E =9.56%.

[0177] Verification Example 1 :

[0178] The PAE effective component content of sample A was quantitatively detected by internal standard method using nuclear magnetic resonance hydrogen spectroscopy, and the effective component content of PAE was measured to be 9.39%. This result is highly consistent with the nuclear magnetic resonance detection result in Example 1, further verifying the accuracy of the method of the present invention.

[0179] Comparative Example 1-1 :

[0180] Same as Example 1, except that:

[0181] The acid-water ratio is 1:1 (i.e., the acid-water ratio is 20.0 mL: 20.0 mL = 1:1), the reflux time is 2 h, the hydrolysis temperature is 200 ° C, the esterification temperature is 50 ° C, and the other conditions remain unchanged. The sampling amount of sample A is 0.1097 g. V =20mL, f =500, f 0 =100, V 0 =5mL; f 1 =100, V 1 =1mL; measured C =355.83 μg / L, C 0 =0.0μg / L, C 1 =0.0mg / L, and the PAE active ingredient content is calculated according to formula (1): E =4.90%.

[0182] In this experiment, the lower hydrolysis temperature and relatively short reflux time may lead to incomplete hydrolysis reaction, resulting in low content of effective ingredients. Although the acid-water ratio of 1:1 can provide a certain acidic environment, the hydrolysis temperature is not enough to fully decompose the PAE components in the sample, thus affecting the test results.

[0183] Comparative Example 1-2 :

[0184] Same as Example 1, except that:

[0185] The acid-water ratio is 1:1 (i.e., the acid-water ratio is 20.0 mL: 20.0 mL = 1:1), the reflux time is 3.5 h, the hydrolysis temperature is 250 ° C, and the other conditions remain unchanged. The sampling amount of sample A is 0.1151 g. V =20mL, f =500, f 0 =100, V 0 =5mL; f1 =100, V 1 =1mL; measured C =582.26μg / L, C 0 =0.0μg / L, C 1 =0.0mg / L, and the PAE active ingredient content is calculated according to formula (1): E =7.64%.

[0186] Increasing the hydrolysis temperature to 250°C and extending the reflux time to 3.5 hours significantly improved the decomposition efficiency of PAE, and the test results were improved compared with the comparative example 1-1. However, the settings of the acid-water ratio and the esterification reaction temperature were still not optimal, resulting in the active ingredient content not reaching the optimal value.

[0187] Comparative Examples 1-3 :

[0188] Same as Example 1, except that:

[0189] The acid-water ratio is 1:1 (i.e., the acid-water ratio is 20.0 mL: 20.0 mL = 1:1), the reflux time is 5 h, the esterification reaction temperature is 90 ° C, and the other conditions remain unchanged. The sampling amount of sample A is 0.1014 g. V =20mL, f =500, f 0 =100, V 0 =5mL; f 1 =100, V 1 =1mL; measured C =422.03μg / L, C 0 =0.0μg / L, C 1 =0.0mg / L, and the PAE active ingredient content is calculated according to formula (1): E =6.29%.

[0190] Although the hydrolysis reaction was more complete at a higher hydrolysis temperature (275°C) and a longer reflux time (5 hours), the esterification reaction temperature was too high (90°C) and may cause side reactions or excessive reactions of some components, thus affecting the final test results. The higher esterification temperature failed to further improve the detection accuracy of the active ingredient, but instead led to a decrease in the content of the active ingredient.

[0191] Comparative Examples 1-4 :

[0192] Same as Example 1, except that:

[0193] The acid-water ratio is 0.5:1 (i.e., the acid-water ratio is 10.0 mL: 20.0 mL = 1:1), the hydrolysis temperature is 250°C, the esterification temperature is 90°C, and the other conditions remain unchanged. The sampling amount of sample A is 0.1008 g. V =20mL, f =500, f 0 =100, V 0 =5mL; f 1 =100, V 1 =1mL; measured C =351.87 μg / L, C 0 =0.0μg / L, C 1 =0.0mg / L, and the PAE active ingredient content is calculated according to formula (1): E =5.27%.

[0194] In this experiment, the acid-water ratio was too low (0.5:1), which may have resulted in insufficient acidity in the reaction medium, thus affecting the adequacy of the hydrolysis reaction. Although the hydrolysis temperature was moderate, the esterification temperature was too high, which again raised the possibility of side reactions and ultimately led to a low test result.

[0195] Comparative Examples 1-5 :

[0196] Same as Example 1, except that:

[0197] The acid-water ratio is 0.5:1 (i.e., the acid-water ratio is 10.0 mL: 20.0 mL = 1:1), the reflux time is 3.5 h, and the other conditions remain unchanged. The sampling amount of sample A is 0.1110 g. V =20mL, f =500, f 0 =100, V 0 =5mL; f 1 =100, V 1 =1mL; measured C =388.79 μg / L, C 0 =0.0μg / L, C 1 =0.0mg / L, and the PAE active ingredient content is calculated according to formula (1): E=5.29%.

[0198] Similar to Comparative Examples 1-4, insufficient acid-water ratio is still the main problem, and although the reflux time is extended, the detection results are not significantly improved. This shows that the combination of low acid-water ratio and high esterification reaction temperature is not conducive to accurate PAE component detection.

[0199] Comparative Examples 1-6 :

[0200] Same as Example 1, except that:

[0201] The acid-water ratio is 0.5:1 (i.e., the acid-water ratio is 10.0 mL: 20.0 mL = 1:1), the reflux time is 5 h, the hydrolysis temperature is 200 ° C, the esterification temperature is 50 ° C, and the other conditions remain unchanged. The sampling amount of sample A is 0.1069 g. V =20mL, f =500, f 0 =100, V 0 =5mL; f 1 =100, V 1 =1mL; measured C =377.05μg / L, C 0 =0.0μg / L, C 1 =0.0mg / L, and the PAE active ingredient content is calculated according to formula (1): E =5.33%.

[0202] Although the reflux time was extended and the esterification reaction temperature was lowered, the acid-water ratio and hydrolysis temperature were still insufficient, resulting in incomplete hydrolysis reaction, which affected the detection accuracy. The final results showed that this combination of conditions could not achieve the best detection effect.

[0203] Comparative Examples 1-7 :

[0204] Same as Example 1, except that:

[0205] The reflux time is 5h, the hydrolysis temperature is 250℃, the esterification temperature is 50℃, and the other conditions remain unchanged. The sampling amount of sample A is 0.1054g. V =20mL, f =500, f 0 =100, V 0 =5mL; f 1 =100,V 1 =1mL, measured C =529.77 μg / L, C 0 =0.0μg / L, C 1 =0.0mg / L, and the PAE active ingredient content is calculated according to formula (1): E =7.59%.

[0206] The experimental conditions are close to the optimal combination, but the extension of reflux time and the reduction of esterification reaction temperature did not significantly improve the test results. Although the hydrolysis temperature is moderate, the long reflux time may lead to overreaction of some components, affecting the final active ingredient content.

[0207] The experimental conditions of the specific embodiments and comparative examples are shown in the following table:

[0208] Table 1

[0209]

[0210] Example 2 :

[0211] Same as Example 1, except that:

[0212] Sample B is used to replace sample A. The sampling amount of sample B is 0.1017g (accurate to 0.0001g). V =20mL, f =500, f 0 =100, V 0 =5mL; f 1 =100, V 1 =1mL; measured C =613.91μg / L, C 0 =0.0μg / L, C 1 =606.7 mg / L. According to formula (1), the effective content of PAE is calculated as follows: E =8.51%.

[0213] Verification Example 2 :

[0214] The PAE active ingredient content of sample A was quantitatively detected by internal standard method using the classic nuclear magnetic resonance hydrogen spectroscopy method, and the PAE active ingredient content was measured to be 8.53%. This result is highly consistent with the nuclear magnetic resonance detection result in Example 2, further verifying the accuracy of the method of the present invention.

[0215] Comparative Example 2-1 :

[0216] Same as Example 2, except that:

[0217] Without performing the sample matrix interference elimination experiment (i.e., without performing step 6), formula (1) C 0 and C 1 The default values ​​are all 0, and the calculated effective ingredient content of PAE is 9.13%.

[0218] Due to the failure to eliminate matrix interference, diethyl adipate generated from adipic acid in sample B was mistakenly included in the determination result of PAE active ingredients, resulting in a significantly higher calculated PAE content. Compared with the PAE content (8.53%) measured by nuclear magnetic resonance (NMR), the test result (9.13%) without eliminating matrix interference had a large deviation, which confirmed the necessity of matrix interference elimination experiment in accurate determination.

[0219] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting the content of active ingredients in polyamide epichlorohydrin wet strength agent, characterized in that: The steps include: (1) Dilute the polyamide epichlorohydrin wet strength agent to be tested with water to obtain a PAE test solution; (2) After adding concentrated hydrochloric acid and the PAE test solution obtained in step (1) into a conical flask, a condenser is installed in the conical flask, and after heating and refluxing the reaction, the reaction solution is transferred to an evaporator bottle to evaporate the solvent, thereby obtaining a reaction solution 1; (3) adding anhydrous ethanol, concentrated sulfuric acid and toluene to the evaporator bottle containing the reaction solution 1, mixing, ultrasonicating the evaporator bottle, and placing it in a water bath for heating and reaction to obtain the reaction solution 2; (4) transferring the reaction solution obtained in step (3) into a nitrogen blowpipe, rinsing, and concentrating the solution by nitrogen blowpipe; fixing the volume with a solvent, extracting, taking the upper layer of liquid and diluting it, and testing it on a gas chromatograph-mass spectrometer to obtain the response value of diethyl adipate of the sample to be tested; (5) preparing standard working solutions of diethyl adipate of different concentrations to obtain standard working solution samples; testing on a gas chromatograph mass spectrometer to obtain the response value of diethyl adipate; plotting a standard curve using the response value of diethyl adipate of the obtained standard working solution sample and the corresponding concentration points; and then calculating the concentration of diethyl adipate in the test sample by the external standard method using the response value of diethyl adipate of the test sample in step (4) and the standard curve obtained above, and recording it as C ; (6) Take the PAE test solution obtained in step (1), add solvent to make up the volume, extract, take the upper liquid, and directly detect the concentration of diethyl adipate using a gas chromatograph-mass spectrometer to obtain the concentration of diethyl adipate, which is recorded as C 0; Take the PAE test solution obtained in step (1) and directly detect the concentration of adipic acid using a liquid chromatograph to obtain the concentration of adipic acid, which is recorded as C 1; (7) Calculation of results Calculate the effective ingredient content of the polyamide epichlorohydrin wet strength agent sample to be tested according to formula (1); (1) Where: E ——The content of active ingredients in the sample to be tested, %; m ——The mass of the sample to be tested, g; C ——The concentration of diethyl adipate measured after hydrolysis and esterification of the sample, μg / L; V ——The volume of solvent required for final volume adjustment after sample hydrolysis and esterification, mL; f ——The final dilution factor of the sample after hydrolysis and esterification; C 0——The concentration of diethyl adipate directly measured without hydrolysis and esterification of the sample, μg / L; V 0——The volume of solvent required for final volume determination when the sample is not hydrolyzed and esterified to test the concentration of diethyl adipate, mL; f 0——The final dilution factor when the sample is tested for diethyl adipate concentration without hydrolysis and esterification; C 1——The concentration of adipic acid directly measured without hydrolysis and esterification of the sample, mg / L; V 1——The volume of the sample before hydrolysis and esterification to test the adipic acid concentration, mL; f 1 – Final dilution factor of the sample when testing adipic acid concentration without hydrolysis and esterification.

2. The detection method according to claim 1, characterized in that: In step (1), the dosage ratio of polyamide epichlorohydrin wet strength agent to water is 0.1-0.5 g:100 mL; In step (2), the ratio of the PAE test solution obtained in step (1) to concentrated hydrochloric acid is 20.0 mL: (10.0-50.0) mL.

3. The detection method according to claim 2, characterized in that: In step (1), the usage ratio of polyamide epichlorohydrin wet strength agent and water is 0.1 g:100 mL; In step (2), the ratio of the PAE test solution obtained in step (1) to concentrated hydrochloric acid is 20.0 mL:40.0 mL.

4. The detection method according to claim 1, characterized in that: In step (2), the heating reflux reaction time is 1.5 to 3 hours; the heating reflux reaction temperature is 250 to 300°C.

5. The detection method according to claim 4, characterized in that: In step (2), the heating reflux reaction time is 2 hours; the heating reflux reaction temperature is 275°C.

6. The detection method according to claim 1, characterized in that: In step (3), the ratio of the reaction solution 1, anhydrous ethanol and concentrated sulfuric acid is 1-5 mL: 20 mL: 1-2 mL; In step (3), the usage ratio of toluene to anhydrous ethanol is 10-30 mL:20 mL.

7. The detection method according to claim 1, characterized in that: In step (2), the reaction liquid is transferred to an evaporator bottle to evaporate the solvent, specifically: the reaction liquid is transferred to an evaporator bottle of a vacuum parallel concentrator, and evaporated by the vacuum parallel concentrator until the liquid volume remains 1-5 mL; In step (2), when evaporation is performed using a vacuum parallel concentrator, the water bath temperature is 40-60°C, the rotation speed is 140-160 rpm, and the vacuum degree is 10-30 mbar; In step (3), the mixing is carried out by shaking; the shaking time is 5 to 15 minutes; the shaking speed is 150 rpm; the vacuum degree during shaking is normal pressure; In step (3), the ultrasonic time of the evaporator bottle is 5 to 20 minutes; during the ultrasonication, the water temperature in the ultrasonicator is 40°C to 50°C; In step (3), the temperature of the heating reaction in the water bath is 50-80° C.; and the time of the heating reaction in the water bath is 20-40 min.

8. The detection method according to claim 1, characterized in that: In step (4), rinsing is specifically performed by ethanol rinsing; nitrogen blowing concentration is specifically performed by nitrogen blowing concentration to 2-5 mL at 40-60°C; and the extraction time is 1-5 min.

9. The detection method according to claim 1, characterized in that: In step (4) and step (6), the solvent is selected from toluene, ethyl acetate, benzene or dichloromethane.

10. The detection method according to claim 1, characterized in that: In step (6), when testing the concentration of diethyl adipate, the solvent used for volume determination is the same as the solvent used for volume determination in step (4); and the parameters of the gas chromatograph-mass spectrometer are the same as the parameters of the gas chromatograph-mass spectrometer in step (4).

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